/diy/ - Do It Yourself

this thread's digits brought to you in part by the CD4516 4-bit presettable up/down counter

I am well aware i can buy fuses online, but where do you buy them locally since radioshack died?

today i hit up walmart, target, lows, home depot, microcenter, and ham radio outlet, and no one had a decent selection.

>>1694524

well, if you live in Milwaukee, you would google ''electronic component stores in Milwaukee'' but if you live someplace else, i have no idea how this can be done. it might be impossible to do outside Milwaukee.

>>1694524
you probably have a local sparky shop and/or maybe even an electronics distributor near you, the few sorts of places I'd expect to stock anywhere close to a full line
also ACE and True Value still have a good selection of hardware things unlike wife's-son's-home improvement stores
but usually I just Pic related or do without

>>1694530
>>1694524
>he uses fuses
That’s a waste of time. If you have a problem with the circuit, fuse blows and you have no idea where the real issue is. If you go sans-fuse, then a specific part of the circuit blows and you know exactly what to fix.

>>1694533
>then a specific part of the circuit blows and you know exactly what to fix.
No.

>>1694516
Is parasitic resistance a real thing? When do we have to worry about it?

When did pic related stop being the standard for 7 segment indicators? I have a pile of these from a while ago, but everywhere I look now, the style is 5 pins bottom/top instead of left/right with gaps.

>>1694524
frys electronics if youre in ca

>>1694516
>that popped cap
Serves you right for using coax on FR-2 dot-board. I'd also blame you for using electrolytic capacitors, but it's still possible that they're there to inject DC down to an active antenna or something along those lines. Use blank FR-4 and go manhattan style. Every component is a surface mount component if you try hard enough.

>>1694557
blame the chinks?

>>1694573
joke's on you, not OC, just some grab that looked like it could have been a photobomb, as it were

>>1694543
any time you go into third world waters

>>1694464
>right next to the vector table
fine thinking. so it's a bit like the 6502's zero page indirect mode, without the indirect from memory (which is more difficult on a RISC machine)
>add to the cost
what technology are you implementing it in?

I know this is really easy and that I could do this with resistors. But the end product I'm going to do will be 8 total connections that will need display leds on if the device is on or off. I feel I know IC's well enough that they should have no problem with 8 inputs and 8 outputs based on them with a bit of work. But I'm not sure what that IC would be. Google searching keeps giving me either chaser/blinker ics, which I'm just looking for an on/off setup. Which I feel would also be really helpful in the future.

OI have fairy lights that have a module that works with a remote control. The module is removable.
I don't know what kind of connection it is, but hypothetically would I be able to plug in an arduino zero w, and then send commands to it? Like on off. I want to pretty much be able to control the lights, from my phone or laptop.

>>1694590
post schematic

>>1694592
>>>/diy/amg/
also google

>>1694595

>>1694447
>DUDE CHILIES OWOWOWOW
heh

>blurples don't provide the best photosynthetic radiation per watt. but the IP65 enclosure is very nice if you're concerned about any topical treatments or mists getting into your lamps.
im not going to do any humid stuff as it would ruin my walls.
was more wondering about the difference in the circuits and power delivery and pros/cons of each.
got a decent answer from anon in another thread here >>>/out/1614606

>>1694543
> Is parasitic resistance a real thing?
Yes.
> When do we have to worry about it?
Any time that it's not going to be negligible compared to other resistances.

>>1694607
elemental sulfur is a dry powder treatment as are many insecticides, whether organic or factory. so maybe still a concern https://www.ehow.com/about_6563528_sulphur-spider-mites.html
that's a fair answer from /out/ if maybe a bit hard on the driverless lights. I've decided on name brand chink (oxymoron not intended) light engines. 30W in a 2cm square. lumens/watt looked respectable for not being Samsung, spectrum looked fair to decent, and they were under $1 each shipped. but I'm doing my own drivers so I have a bit more control over design and build quality
note well, no way to know what's inside the boxes or under the silicone without removing it. the box on those external drivers could be hiding anything, from a Mean Well clone made with dodgy parts and substandard insulation, to a Shenzhen OEM design made to a respectable spec, to the guts of a recycled laptop power brick that will ruin your walls a whole other way
the dudelmao dudes like genuine Mean Well drivers. even with separate light engines from china, they might be cheaper than you think https://www.digikey.com/product-detail/en/mean-well-usa-inc/LPC-60-1400/1866-3154-ND/

>>1694600
congrats, you've solved your own problem
if not, you'll need to show connections to the rest of the circuit and why your drawing doesn't work, because you haven't explained your problem very well

>>1694612
>problem
I don't have a problem. I knew this way would work. I was wanting to see if it would be possible to use an IC for it instead, as later I'll be adding 4 more connections. so it will be 9 inputs/outputs. As my current plan right now is to actually limit it to 2, 9 pin inputs, and each slot being filled with 2 wires from the 9, 9 pin connector/cables to fully populate the two inputs.

So I'm not using pointless connectors everywhere and making the board larger than it really needs to be. I could always just use small ass SMD resistors to do it and shrink it as well I guess.

>>1694614
I think you are looking for the resistor networks/resistor arrays section of your favorite electronics distributor. make sure you're sitting down when you look at the prices
or you could use 1206 resistors. 1/4W just like you're used to. can be handled almost as easily as through-hole components and soldered with the usual 1.6mm screwdriver tip, no problem

>>1694622
Don't believe the Resistor array would work for what I need. As it would be Input 1-5, and each input would have a dedicated LED to it, so if say 1,3,4 have power going to them only 1,3,4 LED would turn on. So the array doesn't seem possible with it's single input to multiple outputs.

And from what I calculated before I would need 1.2k and .5W resistor to power a common green LED off 24v, give or take a small amount. I do appreciate the help though.

>>1694625
>>1694622
Actually, I think this resistor network might work just fine. Didn't realize that the network was a straight through, while the array was more of a split.

https://www.ttiinc.com/content/ttiinc/en/apps/part-detail.html?mfrShortname=BOU&partsNumber=4116R-1-122LF&customerPartNumber=&minQty=25&customerId=

>>1694612
>elemental sulfur is a dry powder treatment as are many insecticides, whether organic or factory. so maybe still a concern
not sure i follow, you mean this is an issue from the lights or from insecticides i would spray on the plants? just fyi im not gonna spray anything but neem oil and soapy water.
the price for those mean well drivers is reasonable if i were to setup something bigger after i move from this shitt 1room apartment, but for the time being those driver/cob chink combos will suffice.
also, would need to fine a EU supplier cus our postal service is anal about non-EU packages paying tax.

thanks

ps rate my shrinkjob

>>1694645
Why did the earth heat shrink split?
When I'm doing a cord like this, I usually bulk up the wire shrunk area with electrical tape to bring it close to the same thickness of the wire. It looks better aesthetically and adds strength to the union so it doesn't fail when flexed as easily

>>1694672
it got heated when i soldered it so i had to cut it open a bit to pull it over.
some tape is a good idea, will try that next time.

>>1694684
>>1694645
desu i think i'll try one of these next time for convenience, with a thinner and longer cable cus this pc power cable i used is too short and heavy.

I'm here with a bit of a weird one:
I'm doign a small side project, using a keyboard. Since I'm a rather frugal person, I tried keeping cost as low as possible and got a free keyboard (I found it on the street, still works, had to clean it a bit though).
What I am trying to do is cut it in half, and connect the traces again, with wires, so I have two functioning halfes.
This would mean I would not have any problems with the IC, as I would not touch it.
It's a shitty rubber dome one though (pic related) and I can't really solder stuff to it, because it would melt.
Any ideas how to still do it or does it make more sense to just buy a used shitty keyboard with an actual PCB?


Also if I do decide to get a cheap used pcb keyboard, I never tried cutting traces and replacing them with wires, it probably makes sense to just cut the trace and instead of attaching the wire to the trace, look for the closest contact right?

Do rotary encoders need debouncing? I have the ordinary one that looks like a potentiometer and I thought that turning it by one step just gives you one square wave bump but instead i get this. Each division is 10us.
Or is it supposed to do that? But thats weird

>>1694686
from what i gather, ribbon cables are similar and i never seen anyone repair those.
would highly advice against trying it on those membrane keyboards.
also, are you aware you can buy quite cheap split keyboards? can probably find a really cheap one from one of those chinese sites like aliexpress.

>>1694689
>also, are you aware you can buy quite cheap split keyboards?
yes, but I really enjoy building or hacking dumb electronics for the sake of it. This isn't about making sense, I just want to have fun with it. Also I have some other ideas how to make it more interesting down the line, seperating the keyboard for that is the first step.

>>1694687

>>1694690
i figured that was the case. i'd suggest finding a cheap or used mechanical keyboard then.

>>1694689
would highly advice against trying it on those membrane keyboards.
I kind of thought so, thanks.
Pic related is someone who did something similar, but that looks like it's gonna be destroyed the second there's any mechanical stress on it.

>>1694692 was meant for >>1694689.

>>1694693
>>1694695
yeah, all the laptop repair vids i've seen they always remind you to be super careful with ribbon cables and they are pretty much the same thing as those membranes from what i gathered.
you're going to have a lot more fun with a proper pcb and easier to fix the enclosure for it aswell, plus any other mods you want to try will be easier.

>>1694698
btw you can also order individual parts for mechanical keyboards quite cheaply from the same site(s) i mentioned earlier

>>1694687
I have two rotary encoders I bought from Adafruit for 4$ each a long time ago. The description on the store page says "This rotary encoder is the best of the best, its a high quality 24-pulse encoder". Not sure if that's a lie but it definitely works like ass without debouncing.
I used the Bounce2 Arduino library to get it working reliably (configured with 2ms interval).

>>1694700
I'll do some scouting, if I can find a used cheap one it's probably cheapest to take that apart, if I can't find one, I'll have to buy the parts.

>>1694703
I figured it out. There was some hidden shit hw stuff sharing the pin i was using that was not on the do not use pin map so i used another pin and it's fine now
I really hate bugs like this

>>1694645
only saying you should be careful with powders and in particular sulfur. I don't know about other insecticides and their compatibility with the soft polymer coating on a COB but it seems wise to exercise caution and hope you don't get mites. in any case the problem is neatly solved if you place the COB in an appropriate luminaire

>>1694686
>I have junk, what do?

>>1694707
>I have junk, what do?
My issue is the opposite though, so I don't think I'm what is meant by that rule.
It's not that I have junk and am asking what to do, it's that there's something I want to do and I am asking if I can do that with my junk or if I have to invest some cash into it.
Junk that you can use isn't junk.

>>1694633

if you put the resistors on the ground side of the LEDs, then you can use a resistor array (aka resistor network), where the common pin goes to ground. this means you use one chip, not two.

>>1694707
im not going to use any powders or sulfur products so i should be fine, but noted, thanks.

>>1694633

if you put the resistors on the ground side of the LEDs, then you can use a resistor array (aka resistor network), where the common pin goes to ground. this means you use one chip, not two.

>>1694685

those things are dangerous unless enclosed. you invariably end up with bare wires hanging off the screws, giving you shocks when you didnt even ask for shocks.

>>1694708

it's rare, but i did find two Razer Blackwidow PCB keyboards with mechanical keys at the thrift store for $5 a piece.

>>1694724
>those things are dangerous unless enclosed.
true, i'll probably get one with cable clamp and enclosure just to prevent coming loose from tugs on the cable, but if i used that picture one it will be above the lights near whatever i use to hang them and wont be fiddled with while turned on, and all of them will be going thru a main switch and can be unplugged separately if needed.

Any resources to to teach oneself radio frequency? What would be some prerequisite knowledge needed to understand it?

>be me
>be a dumbass
>build current sense amp with 6001 op amp
>confuse myself with not exactly clear signal names
>months later...
>get boards back
>test current sense amp
>wonder why no output
>find I reversed inputs of op amp
>fug_XD.kicad_mod
>put 6001R op amp on next digi-key order
>mfw

>>1694732
arrl.org
>>>/diy/ham/

>>1694578
>>1694609
Do you guys know what causes parasitic resistance?

>>1694746

- impurities in materials.
- using the wrong materials.
- horny electrons that will tunnel through anything to get proton pussy.

>>1694750
>horny electrons that will tunnel through anything to get proton pussy.
cringe

>>1694767
virgin insulator detected

What is a good cheap source of large capacitors? I want to make a ghetto spot welder but dont want to spend a lot on brand new capacitors. I'm wondering if I can go to a second hand store and look for a specific old appliance/device that already has them inside that I can extract

First time using KiCAD, I'm trying to build a MIDI controller, I have a matrix of 4x3 potentiometers, what's the 'best practice' for wiring? I would not be mounting them directly on the board since I'm also wiring arcade buttons. I also am not sure if I should 'bridge' common voltage and common ground connections on the potentiometers or set up 12 voltage and 12 ground pins on the PCB.

Also any resources to get better at drawing schematics would be appreciated, I would like to git gud at this.

>>1694737
>6001R
What the shit, I didn't even know they made those. Did you try bending the pins so you could solder it on upside-down?

>>1694684
>so i had to cut it open a bit to pull it over
stick needle nose pliers in there and open them a bit to stretch it back open
slip it over the joint and apply heat to shrink it

>>1694724
>if you put the resistors on the ground side of the LEDs
Shit, I guess my understanding isn't as good as I thought. I had always figured that for an LED(or any component) to not burn out the voltage drop from the resistor had to be before the it.

>>1694912

>>1694912
voltage is a potential difference between two points.
the 0v or ground label that you apply to one node of a circuit is completely arbitrary.
americans make this 10x worse by calling 0v ground and confusing it with earth ground potential as something special. its not special its completely arbitrary.
the 0v ground of your battery in your circuit isn't at the same potential as the earth ground in your wall outlet. they are not connected, no current can flow, the difference in voltage cannot be measured in theory or practice.

voltage is arbitrary.

So I just built this, I don't have a signal generator, just a phone, tablet and speakers. It is suposed to modulate the sound from the bottom diff pair with a low frequency coming in the upper ones. It *works* but if I put the sound in using a capacitor then there are loud ticks and tocks and screeching but if I bypass the capacitor it "works" but with a distorted low frequency wave (it's a triangle but gets squarier).
My question to you is, what the fuck? Don't cellphone/tablets audio outputs do not like capacitors? The ticks are periodic and of only a couple Hz.
>>1694912
It makes no diference with the exception of when you are designing important things and need to think about ESD paths and optocoupler shit.

>>1694959
>>1694942
So as long as the total voltage drop on a line equals the input all components on that line will be fine and not burn out? Doesn't matter the order?

>>1694959
idk, did you try considering input and output impedances?

As a note, thank you guys for helping me out. I was able to figure it out, it functions as the way I thought it would, but I also learned that I could do it with the array which I was not aware of. Much appreciated.

>>1694988
You can also just use one resistor if only one LED will be on at at time. Or if you don't care about the brightness changing.

>>1694990
The initial design will only have 1 LED on at a time, but the additional 4 I'll be adding later may be on at all times. So I could do a bit were the 5 are connected to one, and the other 4 are connected to a array. But this is still just initial concept for it. I'll need to build one and see how I'm going to use it to test the system it's going on. Then I'll make more needed changes. But I appreciate the insight on this. My biggest goal really is to make it as simple and efficient as I can. I'm not so big a fan of brute forcing it, which was why I asked initially if there was another way besides all having their own dedicated resistor and lines.

>>1694991
Well there are LED driver ICs. Also some ICs that your circuit might already be using or that you could easily swap to may have their own current-limiting or collector resistor, I'm pretty sure 74LS logic ICs have ~100Ω from collector to Vcc (picrel), possibly with a diode drop or two in there to drop a little more voltage in case you have a 2V red LED. In any case I always see Ben Eater chucking LEDs on his ICs without any resistors and they seem to last a while, even if they do have more than 20mA through them.

>>1694819
think ahead to when you have to replace a pot that's gone scratchy. you'd want some way to easily disconnect and replace an individual pot, which depends a lot on what's available to you both in your component stock, distribution channels, skill set, and tolerance for repetitive tasks. for a lowest-common-denominator cheap-af way, a series of three-pin 2.54mm pin headers and "Dupont" connectors would be very convenient, and would also allow you to swap tapers, order, and values of pots if desired
>git gud
look at more schematics for systems at and near the level of complexity you would consider building. like any other language, écoute et répète

>>1694834
this proto has seen a lot of hot air over its life and has a lot of test points in the form of tacked-on bodge wire, so I didn't get around to testing my theory just yet

>>1694959
read the OP FAQ
and get a signal generator

>>1694991
did you check the power rating of all your resistors? those in an array might have a lower power rating than discrete resistors
>brute force is bad
quite to the contrary, my dude. repetition is a good thing in electronics. outside of especially constrained critical requirements, it's usually more time, trouble and cost to add a line item to the bill of materials than to add another piece to a line already there. the power rating of these resistors is just one example

>>1695004
stop idolizing that fucking hack
also Pic related

Just watching a video by Andreas Spiess (guy with a swiss accent) about how SDR works, and I never realised how simple the receiving circuit was. But from what I see even though they only have a bandwidth of 2 - 30MHz or so (since mixers are used to get up to the GHz ranges) and only have 8-14 bits of resolution, the ADCs are pretty sub-par. Compared to something like this:
https://octopart.com/wm8224csefl-cirrus+logic-53059007, which can be a 16-bit ADC at 40MSPS, for under $5. So all I'd need is one of those, some sort of frequency generating circuit (square wave vs sine wave circuits that I'd need to research)
And then get some sort of medium-speed USB interface that I can get to work with GNU-Radio. Is there anything particularly wrong with this idea?

>>1695036
>power rating of resistors
The network I first listed was good to 2.25W per element, which was well over what I needed, ideally going with another array and I've found several that meet my power ratings.

>>1695041
>2.25W per element
All at once? Sounds like closer to a total rating to me, can't imagine a DIP package dissipating 10W too well.

>>1695042
It only needs to dissipate .5W at max at a time in the design I listed.

>>1695040
>Is there anything particularly wrong with this idea?
yes. the biggest one is: where's your quadrature channel?
>some sort of frequency generating circuit
don't bother, anything you can build will drift more than a digital source. AD9850 is a pretty standard sine-wave LO in hamland these days, Si5351 is good for square waves

VTR guy back again, >>1692762
NTSC generator arrived, and good news, it actually works with the MONITOR input on the VTR. However the colors are WAY off. Haven't made any adjustments yet but I have a ways to go.

>>1695050
>quadrature channel
Two mixers and a phase shifter? Not sure how expensive those will get.
>don't bother, anything you can build will drift more than a digital source
I was including digital sources in that idea. Like the digital versions of PLLs or whatever.

>>1694834
lol I'm a dumbass nigger, it's the power pins that are reversed on the R, not the inputs. I need to start putting better bleach in my coffee in the morning

>>1695036
if you want to distinguish f(LO+x) from f(LO-x), you need a quadrature detector
>expensive
the SA612 is cheap, relatively speaking. a dual 4:1 analog mux may be cheaper, look up the quadrature sampling detector, aka the Tayloe detector (sic) which Tayloe muntzed the hell out of in a presentation years ago
>digital
ah ok. fortunately the digital solutions are generally pretty easy to configure into a quadrature relationship, there may be an ADI app note for the AD9850 covering this. istr the Si5351 has been made to do it, but it's fiddly. any single-phase clock can be divided by 4 and made into I and Q square waves with a 2-stage ring counter of DFFs
>medium speed USB
there's low speed (1.5Mbps), full speed (12Mbps), high speed (480Mbps) and super speed (whatever). the usual way to USB HS is the EZ-USB FX2, used in e.g. the Saleae Logic analyzer and clones. there are also a few ARM MCUs with USB HS device interfaces (NXP, maybe some ST) but I haven't touched them and they're not quite jellybean priced. note, USB HS has layout requirements you must follow in order to work well

holy shit lads, JLCSMT is open to the west

holy shit lads, JLC SMT assembly is now open to the world

>>1695004
> see Ben Eater chucking LEDs on his ICs
no idea who that is but either the IC is a current sink with a resistor in it or he is just plai retarded.

>>1695157
being born in brazil was a bad choice

>>1695198
definitely option b

>>1695200
the $2 special is all the time, for the first board in your order, if I'd known about that sale I would have fixed up a couple of new revs
anyway the USA is right behind you

>>1695205
>8 trumps = 34 reais = a decent meal in a good restaurant
>20 days
>mail mob kidnaps your shit and makes you pay 15 reais (3$) to get it if it is from abroad

>>1695214
>15 bolsa nero
merchant happens, huefriend

What kind of multimeter should I get? Or do I even need one? I'm just dicking around on a breadboard with LEDs while learning logic. I never used any resistors or capacitors or anything in my classes but I managed to acquire a fuck load of components and I figure a meter would be helpful now that resistors are involved while I learn wtf is going on.

The only bad things I've heard about cheap ones are people talking about how they'll kill you when probing high voltage systems or something. I'm just using a little 5v power supply on a breadboard, or sometimes just a 9v battery. Will the accuracy on a cheap meter be okay?

>>1695258
I would look for a super cheapo 830B multimeter.

>>1695258
I started with one of these a couple of years ago. It's like music, don't buy an expensive instrument until you actually know how to use it. How many electronic keyboards become tables/clothing hangers this way kek

>>1695036
wtf anon, very helpful, thanks a lot <3

>>1695294
The 830 is probably the archetype of 'the first meter'.

>>1695305
needs more blue to match the Hakko
and red to match the Playmobil

>>1695307
too late

>>1694959
mobile device output "ground" isn't actually ground
https://d3uzseaevmutz1.cloudfront.net/pubs/appNote/WAN0131.pdf

>>1695066
as a followup, would a scope like this work for this unit? i'm trying to spend the least money as possible
$80, and its in the same city as me so i could try to avoid shipping
https://www.ebay.com/itm/HP-54603B-Oscilloscope/153620855915?hash=item23c4843c6b:g:9AMAAOSw0DpdZgVi

>>1695450
or something like this?
https://chicago.craigslist.org/nch/ele/d/skokie-hitachi-mhz-oscilloscope/6993691974.html

>>1695340
Thanks! And yes, that pic sums it up pretty well. I had a faint idea of what is going on because there were some time constants on the oscilations and noises that were not present in any components in the circuit.
Fucking chinks.
>>1695450
>>1695453
Check the bandwidth, if it fits then it's good. I don't know how americans can have so many cheap scopes on ebay/craigslist. Here in brazil you can't find them at all and people sell them for an eye and a leg..

>>1695450
im not sure about the requirements to to work on television viewing/broadcasting equipment, but if you want a used scope that will be worth a damn pick up a tektronix. and tektronix probes for it. tektronix 465 is 100 mhz, the 475 is 200 mhz. http://w140.com/tekwiki/wiki/ also see https://www.mouser.com/pdfdocs/Tektronix12_things_to_consider1.pdf particularly page 5 the bottom of which states
>For digital signals, oscilloscopes must capture the fundamental, third and fifth
harmonics or the display will lose key features. So, the bandwidth of the scope
together with the probe should similarly be at least 5x the maximum signal bandwidth for better than ±2% measurement error – the ‘five times rule’. This is also needed for accurate amplitude measurements.

>High-speed digital, serial communications, video and other complex signals can therefore require scope bandwidths of 500 MHz or more.
>>1695503
its "an arm and a leg"

>>1695514
>>1695503
It seems like I only need a 20 or 30mhz range scope at min for a VCR, im gonna contact the guy and see. hopefully he has both probes

>>1695526
also I need a frequency counter. someone recommneded me this, but I have no idea how it works, do I need to hook it up to a radio? how do I attach it to my VTR?
https://www.ebay.com/itm/0-1-1100MHz-1-1GHz-Frequency-Counter-Tester-Measurement-F-Ham-Radio-PLJ-1601-C-/121840965555

>>1695545
Or you could not buy chinkshit?

>>1695547
thats a nice looking freq counter but this will be for a one time job and guaranteed ill never use it again. id be better off trying to find a boomer to borrow one from in chicago lol

>>1695548
That's probably the better option. At least then you can get readings you can actually trust.

>>1695549
Fine fine, how about this
https://www.ebay.com/itm/Fluke-Instruments-Model-1910A-Multi-Frequency-Counter-Tested-Good/143405209439?epid=1807743973&hash=item21639dd75f:g:~f8AAOSwbb5dkkKA
or this?
https://www.ebay.com/itm/Hewlett-Packard-Model-5314A-2-Channel-Universal-Frequency-Counter-Module-2/123927305204?epid=1400656473&hash=item1cdaa49bf4:g:k7YAAOSwTaxdN1np
will they let me get to 3.579545Mhz?

I don't have one arm, the joke is on you.

>>1695554
I meant using a boomer's frequency counter for a one-time use. That or if you have access to one at university or your job. Or maybe one of those stupid makerspaces if you're lucky and they aren't too snobby about you using the equipment. I mean if you do decide to buy one though either should work for the measurement you want to make. The Fluke measures up to 5Hz-125MHz and the HP up to 10Hz-100MHz on channel A and 10Hz-2.5MHz on B. Of course the HP appears to only have 6 digits so you will only be able to resolve to 3.57954MHz. The Fluke should not have that problem, assuming you cal it or feed in an external reference frequency, typically 10MHz.

>>1695558
I really dont think a makerspace would have old tech like a freq counter but who knows. The fluke isnt too bad and I could just resell it.
how do i put in an ext frequency on that? the BNC port on the back? does it have to be 10mhz? my NTSC generator has a 30mhz out bnc on it, could that work?

>>1695560
>I really dont think a makerspace would have old tech like a freq counter but who knows.
>old tech
>like a freq counter
what did they mean by this?

>>1694959
Ok so I got this working. i'm the same dood that made a phaser pedal last week, now I just did the same thing because I coudn't stop thinking about a way of making one without autistic hand made optocouplers.

The gilbert cell is fucking SENSITIVE, I had to make the guitar signal be almost sub mV for it to not saturate and screech like hell. That happened because I soldered a 100 ohm resistor in place of a 100k at R8 (it's 1k there but I forgot to change it)

Added a opamp pre-amplifier. I can get a bit of fuzz deppending on settings too.
Things to do
>sprinkle 0.1uf caps everywhere so it stops amplifying supersonic noise and random shit.

Electronics are cool

>>1695560
Yes, the BNC on the back. Flip the switch back there from int to ext. It does need to be a 10MHz signal. The internal reference oscillator is 10MHz and any external should be the same frequency. You could divide down your 30MHz signal with a simple counter configured to divide by 3.

>>1695584
>get a 10mhz generator
i feel like im falling down the rabbit hole here lol, first i bought a NTSC signal generator, next i'm buying a Scope, now im buying a frequency counter, then a 10mhz reference..... all for a VTR of my dad's tapes from the 70s and 80s that's mostly tv shows taped off local stations

>>1695258
ANENG 8009 if you don't mind something 3 times the price of an 830B.

>>1695294
but don't try to learn on a cigar box guitar either

>>1695514
>arm and a leg
foreign exchange rates vary, especially in Saudi Barbaria

>>1695547
the advent of digital cellular communications demanded higher precision frequency sources for cheap. I'd trust the new counter with the fresh, un-aged xtal to the old name brand unit that nobody but Jesus knows what troubles it's seen. the shitty $14.88 freq counters are fine, mine was within ±10ppm as found
he just needs to get it within a few tens of ppm so that the color reference signal doesn't shift unacceptably over the course of one scan line, about 1/15734 second

>>1695560
the chink counter uses a VCTCXO. there's a trimpot for fine adjustment (range is ±a few tens of ppm or less) on the back of the counter which you use to adjust it to the calibration frequency. but see above

>>1695595
this is the correct answer. it will serve you well for years, not only on the bench but around the house and car

>>1695603
so there's a chance if i buy the $15 bit it wont be correct out of the box? id still have to get a 13mhz signal calibrator?
i noticed too that it has a tiny two pin connector for RF, how can i get that to connect to the circuits on my vcr?

>>1695595
>>1695293
>>1695294
Since I couldn't find one of those on Amazon that shipped with Prime, I just went to the store and got this. Was this a mistake?

>>1695610
>no autoranging
>no AC current
>no backlight control
>no ncv
>no min/max
>probably no true rms
>>>>amazon
There were probably better options from amazon prime if you needed it immediately, though I can't speak for the price difference. If you didn't need it immediately then you fucked up. Even if you did you could have got a 830B for pretty cheap or even for free with a harbour freight coupon while you wait for your 8009 to arrive.

>>1695612
I can just return it. I literally just found this in a box in a corner and took it. 20 bucks. I have no idea what any of those things you listed are, though.

>>1695606
>correct
that's relative. you don't need a metrology lab for the purposes of ballparking a chroma subcarrier. it would be extremely unlikely for it to be more than ±50ppm out as found, which is about ±180Hz. you can use that to reduce the phase shift to 3 cycles through the rainbow per field instead of hundreds. but, the transmitter sends a "color burst" phase reference ~16000 times per second so that the receiver's phase reference stays aligned to that of the transmitter. the effect of the chroma subcarrier being off is exactly the rainbow shifts you're seeing
if you're not familiar with an NTSC color video signal, please see one of the many tuts. the first two parts of https://sagargv.blog spot.com/2011/04/ntsc-demystified-part-1-b-video-and.html are essential reading
repost that color play board schematic and let's see what we're dealing with here. there is probably a test point, and you may have to open the frequency control loop to align the crystal oscillator separately from the rest
>two pin connector
I won't tell anyone if you just tack a couple of pigtail leads on it. JST XH connectors are jellybean enough to be disposable

>>1695610
3½ digits is enough to get started until you have to worry about microvolts, which you probably won't if you're juts farting around with micros. I'm a big fan of the current inputs being separate from the voltage inputs. it's harder to do stupid shit that way. not a big fan of the resistance inputs being separate from the voltage inputs, but that's just me being lazy

>>1695612
>>>/g/

>>1695613
$20 isn't bad for that for a brick and mortar. if you don't need bells and whistles and toys, you did good
besides, amazon subsidizes fake news, but that's a discussion for another board

>>1695613
>I have no idea what any of those things you listed are
A bunch of features that range from "I'll never use it" to "actually kinda useful" that you can get almost all of on the AN8009 for $22 on ali (with ~15-30 day free shipping)
https://www.aliexpress.com/item/32842548196.html (looks like a pretty reputable seller)
It also automatically detects AC or DC on both V and A ranges, and I assume you can swap between the two with the select button in case you have a mixed AC and DC signal to measure.

>>1695614
>>>/g/
Sure they're moot points depending on what you were doing, but I bet you you've at least used one of those before, right?
>inb4 at /diy/ we make our own DMMs

>>1695616
yes, and fuck autorange right in the jannies' asses
also, when/if you yuppies grow up, you'll learn to be content with what you have and can get in due time instead of (((optimizing))) all the time

>>1695614
>left side color REC
>right side color PLAY

so i can just pull the black wire of the XH to a gnd point and alligator clip the red wire to the terminal point? seems doable. ofc, china shipping means I'll be waiting two weeks. but I'm in talks with someone on CL to get a 40mhz scope this week so I can at least start checking scope points.
thanks for that link I'll get reading on it to see what I'm dealing with, all the info you just gave about how the chromasubcarrier works was new to me but interesting.

>>1695628

when choosing scopes, choose the one that has more TV-related functions, like this one which includes filters for isolating horizontal video signals, and vertical video signals.

>>1695205
>definitely option b

fuck you, nigger! i just watched Ben Eater spend an hour designing and building a CRC-16 calculator using flip-flops and gates. the mental power necessary to figure that (sorta worthless) stuff out could power a small town for several hours.

When my multimeter is not used it turns itself off, how does that work? How do i do that without a mechanical switch?

>>1695621
This is just an assumption, but aren't the electronic switches actuated by the autoranging controller going to have lower impedance and with lower stray capacitance and external noise-coupling?

>>1695635
>TV-related functions
Not him, but am I ever likely to use those without a CRT TV/monitor? Can they be handy for troubleshooting VGA signals? I bet that video synth guy gets a lot of use from them though.

>>1695641
There either be a small power management IC that cuts power to the main controller and monitors battery level, or all that stuff is done in the main controller and it just enters sleep mode by itself going off an internal timer. The latter will probably have a higher quiescent current than the former. To do it yourself without just going the easy route and buying an MCU with a decent power-saving mode, you'll need some sort of simple timing circuit that doesn't have a high q-current. That means stay well the fuck away from a 555 timer. A monostable or bistable circuit could both be made to work here, depending how you want your reset to function. You also need to ensure that your timer is retriggerable, and that your MCU triggers it each time it detects itself being used. Something like pic related could work as a timing circuit in a pinch:
With the arrows leading towards the set and reset inputs of the latch respectively (possibly with inverters in there). Here the gate threshold voltage of the P-type FET is being used to judge the voltage of the RC circuit is approximately above a certain level. With this FET arrangement, when the circuit has entered sleep mode there should be no current flowing through the FETs. Probably fine for simple timing like this, a factor of 2 or 3 won't make a difference.

also ignore the fact that the MCU could do the timing itself, it still applies to a simpler circuit without its own oscillator

>>1695647
Oh yeah that definitely needs an inverter on that set line, again using one that doesn't have significant current flowing when the circuit is sleeping (N-ctype FET + pullup resistor).

>>1695635
>CRC
oh yeah that was mind-blowing how he used shift registers and XORs to do that kind of mathematics

Someone in the last thread wondered why the even earlier /ohm/ had been deleted
ban & wipe

I'm using a DC relay that puts out 24V 10A max, so 240W. I have a water chiller and a water heater that run on 24v, however the chiller is up to 400W, and the heating element is up to 600W.

I dont actually need more than 240W of cooling or heating capacity, can I just give it what the relay puts out or will it kill my relay.

here is the heating element: https://www.amazon.com/dp/B00KO32AB0

here is the relay
https://www.ereshop.com/shop/index.php?main_page=product_info&products_id=767

>>1695655
maybe it would help to add Ill have thermostats in between the relay and the cooling/heating devices.

I could maybe use that to throttle the power? Setting a low error and feeding the analog signal a close temperature reading so it doesnt try to go full power.

>>1695652
the more data your browser harvests the less captchas you get

>>1695628
excellent. you don't really need a freq counter to try to ballpark that 3.58MHz adjustment. grab a jeweler's screwdriver and try to make the bars widen and disappear. if the rainbow narrows, turn the other way, if it reverses, use a lighter touch. if you can't successfully make the adjustment, get a 3.579545MHz crystal on order

>>1695647
>lower impedance
they will leak. maybe nanoamps, but more if they are designed to be suitable for higher voltages
>lower stray capacitance
total capacitance would be the concern, and FETs have their own capacitance in the tens of pF. taking a step back for perspective, it's a slow pocket meter, not a scope. at 2Hz, tens of pF are irrelevant
>noise coupling
perspective, again. worry about the 1 meter antenna connected to the banana jacks first

>>1695635
>muh small-batch upcycled artisanal discrete logic
cute for demonstration purposes, almost but not quite a dead end in the age of behavioral synthesis. it is good to get the kids thinking in parallel and in Galois arithmetic (that mouthy little rebel) so they're not completely fucked the second they step outside arduino.cc

>>1695648
better to let the MCU handle the on-time by its own rules, e.g. if you want to auto-off only when the input signal is around 0, and grab its own tow bar so that, when the user requests, it can turn itself off promptly just by letting go. Pic related

>>1695652
>why the even earlier /ohm/ had been deleted
probably explicit dudelmao discussion

>>1695655
1. relays don't "put out". they are just mechanical switches
2. the load will consume whatever power it will and the relay contacts will pass whatever current the load consumes, even to the point of welding together. it's up to the designer (that means you) to ensure that the contact ratings exceed the line voltage and load current ratings
the coil ratings are a separate matter between you, the relay, whatever you're using to control it, and the LORD

>>1695660
>the 1 meter antenna connected to the banana jacks first
BNC DMMs when?

>>1695647
>small power management IC
can you recommend some easy to use one?

>>1695613
I would keep it. It has about 10MΩ input resistance as opposed to 1MΩ of the 830. Do you understand the caveat circuit at >>1695293? The resistance range of 200MΩ is rarely found on other meters.

>>1694533
kek, fuses aren't there just to protect circuit, have fun while your house burns down because you were too cheap to fuse your wires.

If i am a 3.3V powering arduino from a 5V battery, do you think it would be worth it to use buck converter instead and bypass the voltage regulator on the arduino?
With the voltage regulator it is wasting 1.7V depending on battery charge, while buck is 90% efficient and would be only wasting about 0.5V worth of energy
seems like a great way to extend the battery life like by like a 20% or so

>>1695669
Pic related might help you get started on your search, but one probably wouldn't buy it unless extremely low shutdown current were absolutely critical that couldn't be achieved otherwise, only a few such devices are needed, or it's on someone else's dime

>>1695684
when a tripfag is making a mistake, we must take care not to interrupt him
t.Napoleon

>>1695687
your analysis is correct

>>1695689
>Pic related might help y
I looked up some latching circuits and stuff and it was all too complicated and overengineered for my taste so i performed *big think* and came up with this incredibly simple solution that is perfect for me
Basically you press the button which opens the mosfet and allows the IC to boot and then the IC pulls one pin high and keeps the mosfet open and you can let go of the button. This is very fast so you can just barely tap the button and it will work.
And then when the IC wants to turn it self off it just pulls the pin low and boom, mosfet closes and near zero energy gets wasted. disgustingly simple

>>1695692
maybe. have you ever powered a microcontroller or other micropower circuit thru its ESD diodes via pull resistors on its GPIO pins? try it sometime, it's fun
to work around, crank that resistor value way up. to fix, add capacitive (i.e. MOSFET) isolation between the I/O pin and the pass device's gate

>>1695660
>>1695635
The scope i might be getting is a Hitachi V-423 40mhz . looks like it has a TV-H and TV-V mode on it too

>>1695660
>new crystal
I could do that, however, the whole area on the chip is under shielding with massive soldering globs all along the bottom, whats the best way to get it all out? I dont have a solder sucker, just a iron and some braid...

Hi, radiomuggle here. I'm trying to get into the LoRa field, and I bought an Ai-Thinker Ra-01 module to mess around with. This module advertises being able to work in a range of 410-525MHz.
However, looking at the datasheet of the SX1276, the frequency at which the transceiver works is configurable. Two of the factors I know of are the crystal (which runs at the recommended 32MHz), and the Frf register.
If I set the Frf register correctly, can I transmit and receive at 868MHz (the register is big enough to represent this)? If so, why does the product description state only 410-525MHz? If not, what characteristics of the module prevent this?

>>1694524
Consider using automotive fuses. You can make a fuse holder with crimp on spade connectors. Available at most hardware stores.

>>1695722
beautiful. how much did you pay for it again?

>>1695723
do you need to remove that can to make the adjustment? or did you already try to make the adjustment and weren't able to pull the crystal to fix the color?
>test point affordances on top of the can
feelsgood.jpg
since you care about the board, and without seeing the actual joints and pad layout on the bottom of the board, and assuming your soldering iron can put in the heat, the best way would be a solder sucker. I like the spring-loaded plunger type. however you may not be able to get a decent sucker cheaply in a timely fashion (see also the engineer's trilemma) in which case braid might do, though inefficiently. rosin flux is optional but recommended in either case

>>1695724
Pic related, for one example
if you don't know what a Smith chart is, you might not have a good idea what you're getting into with this particular adventure. I suggest you reconsider and get a properly designed 868MHz module instead, and develop enough knowledge about radio systems to pass the exam for the highest class of amateur radio license, even if you don't bother sitting for the exam

>>1695734
radiomuggle here. Thanks for the answer. While I might indeed be a tiny bit in over my head here, I want to eventually try and make my own SX1276-based module, instead of using a preconfigured module, for learning purposes more than anything (and it honestly doesn't seem like the hardware on these modules is very complex, aside from the SX1276 itself). So understanding what causes this limitation is interesting to me.
Now, you mention the power amplifier, but according to the datasheet, the power amplifier PA_HF inside of the SX1276, as mentioned in your screenshot, should be enough to transmit at the higher frequencies. This can be configured through the SPI protocol. So I think that isn't really the limiting factor, either?

>>1695734
havent gotten it yet, but either today or this week. guy wants $65 for it. says it works fine.
>>1695734
I tweaked the screw through the bottom but even minute adjustsments didn't do much for some reason. could be a crystal issue. i cant pull the crystal because its inside the shielding. sorry didnt take a picture of the pcb but here's a bit from the schematic, i circled X501 which I believe is the 3.58mhz xtal. with the yellow shielding box outlined
i do have one of those cheap plunger type ones, didnt think much of it but i suppose I could give it a try

I want to have a basic USB switch, two outputs, one input. I prefered if it recognized automatically if outputs are plugged in, but it can be a physical switch as well.

Does anyone either know where to get them or (since I couldn't find one) what chip makes sense to use to build one. Basically a switch that with one flipping of the switch changes all 4 signals between the pins. If possible, no digital switch then, since those would need additional power etc.

>>1695758
pic related

>>1695758
>>1695759
I just reread that and realized it makes no sense, sorry.
What I wanted to ask:
Are there USB switches like the one in those posts?
or
Are there 3 pin switches like pic related that switch 4 signals at once instead of one? ( with 12 pins then) I'd rather not just use one switch for every signal unless I have to.

>>1695762
You just need DPDT switch for the 2 data lines.

Just bought my first pic related

Am I supposed to get voltage readings when my hands come close to it with no cables plugged in? I get over 8 volts if I touch the insulation on the binding posts

Sorry for the stupid question

>>1695746
it's pure speculation as to what's on that module, what component values, how they're connected, etc. sometimes RF design has an empirical component, to compensate for unanticipated parasitic effects of components, including capacitors and inductors which already have frequency-dependent behaviors even in their ideal forms (it's what makes them useful). if you look up "quality factor" aka Q, you might see some of the complications that go into selecting/using reactive devices
>the limiting factor
>the
it isn't like a CPU that works absolutely fine when underclocked. that is the wrong mindset to apply here. the entire circuit has been designed to convey a certain range of operating frequencies efficiently and without distortion. at UHF, the shape of traces is sometimes use to shape circuit elements. want your mind blown? look into transmission lines, specifically the behavior of the 1/4 wavelength transmission line vs. 1/2 wavelength transmission line
also watch this https://www.youtube.com/embed/DovunOxlY1k
>make my own
that is the correct mindset. you would have better luck just copying their reference design onto a board than trying to reverse-engineer the thing you got. not that you will likely have any of the equipment required to validate it unless you have access to a university's RF lab or tens of thousands of dollars to spend to buy it (at the low end)

>>1695747
yep, crystal's probably fucked and you have found that mofo. you could be cute and just cut the shield off with a utility knife or other least destructive means, and tack-solder and/or copper-tape it back into place when you're done
the crystal could be of a size no longer commonly available (HC18). crystals are also especially sensitive to damage from physical mishandilng, including stress on the seals at the leads. be very careful when you form the new one's leads to fit the board. buy half a dozen, they're cheap

>>1695768
yes, it's that sensitive and you have that much static

>>1695783
to be clear, you're talking about something like this right? i can get a pack of 10 for about $4 it seems
https://www.ebay.com/itm/10-x-3-579545-3-58-MHz-QUARTZ-CRYSTAL-560445-4-HC49-U-COLOR-BURST-NOS-3579-545/362260971914?hash=item54586fc18a:g:PlAAAOSwdJtdCwCj

I've found with this board (after replacing many caps and a few transitors) that the pads are very weak and will separate from the board with mild force when desoldering. fortunately all the copper leads are on the top of the board meaning worst case you solder a wire right from component to component (or scratch off the green and solder right to the copper)

>>1695789
>chopped leads
>nEw OlD sToCk
something like that. but get new stock instead
https://www.digikey.com/product-detail/en/abracon-llc/ABL-3.579545MHZ-B2/535-9053-ND/675248

>>1695671
Nope, don't understand it at all. Don't even know what any of these settings do or which holes I'm supposed to plug the proves into. I think the ground goes in the middle one. I am a complete beginner.

>>1695747
>I tweaked the screw through the bottom but even minute adjustsments didn't do much for some reason

just FYI, when you approach that variable cap with a metal screwdriver, you change its capacity, which detunes it. so, what you have to do is turn it a tiny tiny bit, remove screwdriver, then check if that helped. then repeat 100 times.

or, find a piece of nylon or other hard plastic that you can shape into a screwdriver. then the only thing to worry about is not pushing down on the screw too hard, coz that too detunes the cap also.

>>1695807
Read this.

>>1695763
First of all, thanks, I didn't know the term.
But doesn't a DPDT switch only change 2 data lines? Wouldn't I need 2 DPDT switches? Are dpdt switches with 4 lines called differently?

>>1695763
nvm, I just understoof what you meant. Switch the data lines, power lines can just be connected normally. I should have thought a second about this, thanks.

>>1695783
>yes, it's that sensitive and you have that much static
Makes a bunch of sense, cheers

>>1695783
radiomuggle here.
I wasn't aware they had reference designs for this. That said, it sounds like I have a lot of reading to do to better understand what I'm dealing with here. Thanks for the answers.

Why TRS connectors and jacks aren't used in lab settings? My school had god awful banana plugs that were flimsy as fuck. a good big chad TRS plug would be much better.

>>1695823
cheers
have a bonus link https://electronics.stackexchange.com/questions/334392/sx1276-understanding-matching-network

>>1695825
phone jacks are only especially durable when molded

>>1695795
ah much better

>>1695809
thanks for the tip. im willing to bet the crystal is no good anyways and for a few pennies get a new one, doenst bother me. i will probably have more trouble with the rf shield than actually replacing the crystal lol

>>1695695
>powered a microcontroller or other micropower circuit thru its ESD diodes via pull resistors on its GPIO pins
what is this heresy

>>1695763
>DPDT switch for the 2 data lines
Not at any speed faster than USB 1.0 you aren't.

>>1695825
can't stack them
shit current capacity
shit voltage isolation
less freedom

>>1695825
about one thousand years ago, manual telephone switchboards were obsoleted by the strowger switch. telco stockpiles of TRS connectors flooded the surplus market and got put into all sorts of hobbyist and small-business equipment. it doesn't mean the fucking things are any good at carrying power, or even audio! they were just cheap.

>>1694516
I want to wire some grow lights for a weed plant. Just one, so the light doesn't have to he huge. I'd like to not spend 100 dollars is there a 20 dollar option?

>>1695815
> But doesn't a DPDT switch only change 2 data lines?
It does. Some devices won't be happy about being powered but unable to communicate (e.g. they'll try for a couple of seconds then shut down until power-cycled).

> Wouldn't I need 2 DPDT switches? Are dpdt switches with 4 lines called differently?
QPDT ("quad pole, double throw") or 4PDT ("four pole, double throw"). The "throw" is the number of different positions the switch can have (on-off is single throw, A-or-B is double throw, etc), "pole(s)" are essentially independent switches operated by the same knob/lever/button.

The main thing to bear in mind is that USB has some fairly tight constraints on parameters such as line capacitance, cross-talk, SNR. Slower (USB 1) devices may be more tolerant, faster devices won't be. Switches designed for DC or audio frequencies won't transmit high-frequency signals cleanly.

It it possible to make a load-sharing charging circuit for multi-cell batteries?
I can find tutorials for single-cell load-sharing circuits, but I can't find anything for multi-cell.
I mean, I know it's possible, otherwise laptop batteries would all be single-cell, I just can't figure out how to do it myself.

I'm trying to make a battery power hat for a Pi so I can throw it in my backpack as a portable computer, without having to power it through the USB port and a separate USB battery pack.

>>1695987
The usual approach for a laptop pack is charge the whole thing in series, apply resistor across one cell for a while if that cell's going higher voltage than the others.

>>1695987
the need for a load-sharing circuit is overstated. You can just let the battery charger power the load at the same time it's charging. It may not be ideal but I have the same pi-battery setup you're thinking of and it works just fine. Accepting the battery may only charge fully when it's off.
Why do you need that multi-cell pack? Boost converters are so tiny, cheap, and efficient that usually it makes more sense to make things easier for yourself by using a single cell (or parallel cells).

>>1695918
If you're going to save $80 on lights, spend $40 on a fire extinguisher.

>>1695987
Perhaps you're looking for a "balancing circuit" or "BMS" (battery management system)? Still, just use a booster from 1 or more parallel cells (which don't need balancing) from ~3.7V to 5V. They're smaller than an equivalent BMS.

>>1695725
interesting idea, but doesn't work in tight spots like, say, inside a multimeter.

>>1696026
Put an inline automotive fuse holder on your positive lead, so it pops before your more expensive ceramic fuse does.

>>1696007
What do you mean by apply a resistor across the cell?
Is that actively managed by a circuit, or is that just something you do once before assembly to condition the cell?

>>1696012
>>1696019
Admittedly, power stuff with lithium-ion batteries is a bit outside my electronics expertise, but from the few tutorials I read, you need a BMS even for parallel cells, since differences in internal resistance and stuff can cause one cell to take most of the power while charging.
I figured if a BMS is needed anyways, I might as well get a series battery since you can get them in pretty high capacities.

>>1694573
>Serves you right for using coax on FR-2 dot-board.
What's the issue here? mechanical stress creating an open circuit?

>>1695987
>otherwise laptop batteries would all be single-cell,
lol no. boost converters are inherently less efficient than buck converters
load-sharing is also called power path management by some vendors. for example, Benchmarq (acquired by TI) has a comprehensive line of battery management products with advanced features such as power path management. if you search on that term and 2S, you will find the datasheet for the bq25883 on the first page. there are almost certainly simpler chips for the job
>circuit
every good homemade Li+ control circuit tightly integrates a class D fire extinguisher

>>1696012
it is well short of ideal, to put it mildly. it's reckless and it's shit and you're a pathetic hack

>>1696098
automatic balancers do it every time the cell nears charge completion. look up the S-8209B
>BMS for parallel cells
not necessarily. only build packs with cells that have had the same service life experience (make, age). ensure cells are charged to the same voltage before joining them together in a pack. they will then hold balance between themselves through their service life and you need only worry about balance between each parallel rank when you connect them in series

>>1696103
Actually since it's dot-board there's basically no chance that mechanical stress causes an open-circuit, as the copper traces aren't actually connecting anything (assuming it's dot-board and not veroboard), the connecting solder/wires would have to break for that. Mainly that it's easier to delaminate or otherwise damage with heat than FR-4. Also the whole dot-board thing with an RF circuit (or at the very least high frequency enough to use that tiny choke, a BNC plug and maybe some other type of coax, and wire twisting) when manhattan or deadbug or one of the other styles would likely be a far better idea.

Say I have a 12v 1A wall wart;
what happens if I draw 3.5A from it?

>>1696127
how would you do that?

>>1696127
As you increase the current past 1A, the ripple voltage will increase a bit, then the voltage will drop below 12V, possibly popping a fuse, activating a PTC thermistor, or triggering a fault condition in the control circuitry that limits or entirely cuts off the current flow. If none of these happen, the wall-wart may just pump out 4V or something continuously, or it may burn up the flyback transformer coils or switching MOSFET.

>>1696131
A 3.3Ω power resistor as a load would do the trick, but I assume he means to power a slightly smarter load that's rated at 12V and may pull up to 3.5A.

>>1696127
>breaking news, fat neet dies in housefire

>>1696133
>next up in sports, dog bites man, and in weather, sky is blue

Pic related slips the bayonet into THT power diodes

>>1696132
>A 3.3Ω power resistor as a load would do the trick
Fantasy. Try it and measure the voltage.

>>1696132
thanks, it seems this is probably the cause of my troubles

>>1696133
>33
at least you got doubles

>>1695946
Thanks!

>>1696146
Oh that's what you were implying. I mean, if you read my post you'd understand that I didn't think he would be able to do it either, I thought your question was a "how would you attempt to do so" rather than a snarky "haha try it and see lmao".

>>1696065
do i look like this guy?

>>1696175
Why did you post your avatar?

Any reason why this wouldn't work to power a fan controller and 4x fans? Total Amperage of the fans is about 1A.

>>1696179
if it's your own controller design, post schematic
if it's not your own controller design, go back to the chinkshit general

>>1696183
It's a box standard Evercool 3pin fan controller and works fine with 4 fans off one motherboard pin.

>>1694533
Imagine being this mentally challenged...

>ordered some BNC probes for my scope on Amazon
>they delivered woman's hair spray instead
what the FUCK amazing

God, why is EMC testing such a pain in the ass? Are niche hardware startups simply forced to break the law by ignoring certification requirements, or is there any way to make business sense of having to pay many thousands to get all the certifications you need to bring something to the market, when the product would take years to recuperate it, if at all?

>>1696271

its a hurdle that keeps pennyless developers from stinking up the world with their noise. there's an easy solution tho: move to china, they only cost you'll incur is buying the certification stickers, a dollar for 1000.

>>1696269
>>they delivered woman's hair spray instead

keep trying, maybe next time they'll send the woman that goes along with the hair spray.

>>1696284
>buying the certification stickers
doesn't fool the FCC

>>1696271
you can verify EMC performance for yourself in some jurisdictions, at your own risk of course. maybe it's cheaper to line the whole inside of the device with conductive paint or foil
>inb4 intentional radiator
and that is why there is module certification

>>1696269
>buying anything from the greek jew
that was your first mistake

>>1696303
>the greek jew
Who's that?

>>1696306
Jeff Bezos, oligarch, defense contractor, purveyor of fake goods and fake news

I got this cheap tube guitar preamp online. When I turn it on and plug in my headphones, there's a nasty buzz.
I know it's a cheap preamp and I shouldn't expect much, but this is well beyond unusable.
Assuming it's not the tube that's the issue, I suspect it's the grounding. It's made out of metal and when I put my hand on it, the buzz gets slightly quieter.

Do you think it's the grounding or the faulty tube? How would I go about tackling this besides complaining to the seller (already did).

>>1696303
>you can verify EMC performance for yourself in some jurisdictions
Sure, if you have a hundred thousand dollars worth of test equipment

hey
im looking for some help with electricity/batteries

i have a 2 small engines/motors(like pic) powered by 2xAA batteries
i want to buy a adapter so i can use it from AC no buying or charging batteries

do i go for higher V or A for the engine to perform stronger/better?,

i can get
Output: 3.2 V – 1125MA 3,6va
or
Output: 4.5 V – 800 mA 3,6va

>>1696303
>>1696298
but really, the Scope i;m getting today only has one probe (he doesnt know where the other one is) do I NEED both probes when working on the VCR or is one enough?

>>1696341
some of it can be gimmicked up with the help of a decent SDR. look up EEVblog's low-rent EMC look at the Gigatron

>>1696336
test more.

>>1696347
check the manual and see how many of the scope screenshots have two traces on the screen at once. I'm pretty sure the answer will be 0 so one probe should be fine

>>1696351
neat thanks. I'll cancel the order for the probes

>>1696342
>2xAA batteries
That's 3V (assuming thry're in series) so you want 3 Volts
The current rating on wall warts is a maximum it can supply, the actual current(mA) is determined by voltage and load

>Output: 3.2 V – 1125MA 3,6va
this one

>>1696356
thank you very much

>>1696336
Would something like this help me?
https://www.ebay.com/itm/173939123575

>>1696336
let me try that again... test more
try another power supply if available, the one you're using could be shit
earth it to something
check the tube socket and tube for poor mating
look for loose wires inside. check jacks for proper and secure mating
don't trust chink tubes
if shit persists, post vocaroo

>>1696364
probably not, unless you have it plugged into your computer or phone or tablet etc.

>>1696365
I have another adapter at home that would fit, but it's 1.5A, and the one I got is 600mA, so it would be a bad idea to plug it in, right?
Dunno how to ground it, what should I ground and to what?

I just plug my headphones in. Fuck, I'm super dissapointed.

>>1696336
ground the grounding
no schematic found, only picture

>>1696373
I did some reading and turns out you can plug in an adapter with more amps so I did and it's better. Less noise and now when I touch the metal case, the noise dissapears completely.

>ground the grounding
Can you explain to me like I'm a retard? Thanks.

>>1696378
You could connect the output (OUT) to your amplifier (which is probably grounded).

>>1696386
My amp is dead, that's why I got this one.

>>1696373
Remove the tube and see if the hum goes away.
>386D is the only active component...

>>1696389
Makes noise even without the tube.

>>1696391
does the signal go through without the tube?

>>1696388
Doesn't matter, if it's connected to the mains it's grounded even if switched off. Alternatively find another connection to the mains ground and connect that to the metal case to hear if that helps. Currently the whole thing seems to be floating and touching it partially replaces the ground connection.

>>1696378
>you can plug in an adapter with more amps so I did and it's better.
This is likely where the hum is coming from.
The adapter you're using isn't filtered enough and the device can't filter the rest out.
Connect it with a battery of the same voltage.

>>1696392
No, it doesn't.

>>1696395
I just tried that, connected OUT to my other amp's input and that actually made it worse.
>touching it partially replaces the ground connection
Yeah, I feel like I'm losing it. I feel like I'm so close I wanna grow a third arm to hold that piece of shit while i play.

>>1696399
The other adapter made it much better and now the noise dissapears completely if I touch the metal casing. Don't have a third one to test it out. Well actually I do, but that's the worst one I have, I'll give it a try.

>>1695783
>>1695836
>>1695066
here's the XTAL location by the way, someone asked about seing the board. I suppose I could either try to desolder the RF shield or cut it open and metal tape it up again after..

>>1696399
>device can't filter the rest out
If so, touching the case would have no effect.

>>1696407
You're right. I wasn't paying enough attention.

>>1696404
>and now the noise dissapears completely if I touch the metal casing
connect a wire from the metal case to the screw on the outlet cover your adapter is plugged into

>>1696347
>do I NEED both probes when working on the VCR or is one enough?

you dont need any probes. if you keep it short, just some hookup wire soldered to paper clips at both ends make absolutely fine scope probes.
at the probe end, file the paperclip into a needle point to punch thru flux on a PCB and thru wire insulation.

>>1696399
>This is likely where the hum is coming from.

looks like there's a boost converter near the jacks to power the tube, maybe. that would be a likely cause of massive EM noise in an low-level amplifier.
anyway, it's a meme tube amp for retard hipsters, and shouldnt occupy our attention for more than a few seconds.

>>1696412
I knew it was gonna get down to this. If I don't find another solution (I won't), I'll try it tomorrow.

>>1696347
>do I NEED both probes when working on the VCR or is one enough?

you dont need any probes. if you keep it short, just some hookup wire soldered to paper clips at both ends make absolutely fine scope probes.
at the probe end, file the paperclip into a needle point to punch thru flux on a PCB and thru wire insulation.

>>1696399
>This is likely where the hum is coming from.

looks like there's a boost converter near the jacks to power the tube, maybe. that would be a likely cause of massive EM noise in an low-level amplifier.
anyway, it's a meme tube amp for retard hipsters, and shouldnt occupy our attention for more than a few seconds.

>>1696417
>Olive oil
Ew, no, that's gonna go rancid.
Use mineral oil or paraffin wax.

>>1696417
Where do you get those long high-value resistors? Apart from digikey and all that I mean. Are there common places you can salvage them from? I need maybe 1GΩ as feedback from a very high voltage flyback transformer. Though I'm unsure if I can get reliable feedback with another winding.

>>1696417
>looks like there's a boost converter near the jacks to power the tube,
https://sites.google.com/site/danampvalveamps/amplifiers/diy-low-voltage

>>1696406
hmm, I wish I'd seen that before you sent off for the crystals, I might have had you get the HC-49S surface mount type depending on whether there's room enough below the board to hold it
otoh, the shield can is held on in only two places, patience and flux would get it right off. when you do, post pic inside with a banana for scale
>banana optional, scale mandatory

>>1696417
ikr they should just download a crack of Guitar Rig and never mind this totally performance-unworthy shite

>audio goes through differentiator and back through integrator
>position for clipping the intermediate waveform exists
pretty rudimentary for a prototype, but I can see it being promising. I'll give manhattan-style circuitry a try with this project.

>>1696515

>>1696482
No worries, it was cheap I can always get another one.
Got my scope today. But I’m a total dummy as to how to use it. The manual said touch the tip to the .5v cal tip to get a square wave calibration but nothing happens when I do that

>>1696519
Fuck

>>1696519
How's things in australia? Pretty sure your probe's grounded bro. Set it to DC at that little 3-position toggle.

>>1696526
Ah thanks. That did it. A nice little Calibrated sine wave. Time to take a look at some circuits

>>1696533
That's no sine wave!
Also I've noticed that your trace is significantly bluer than my later hitachi, makes me wonder what other phosphors they use. I'd kill for an orange oscilloscope trace.

>>1696545
Square wave sorry, I had it right the first time. And it just looks blue but it’s reallt quite green.
Okay baby’s first scope adjustment.
See line two on the sheet. I set it to 20usec and .5v, and got this signal. It says adjust to 15V PP, is 15 the grid line that it’s at?

Hey lads I just got a hold of a vintage nad model 90 amp and I was looking for some servicing tips. The only service manual I could find is some sort of fucking bootleg copy scanned with an early 90s cheapo scanner and its barely readable.
I know that the the thing needs a recap starting with the filters which are completely gone as the heavy humming from the outputs suggest. What else should I preemptively replace ? I know that carbon resistors go bad so Imma do away with those too but I'm really worried I will bork this by cheaping out on a component that's going to take the output stage with it. I head that those ball shaped semiconductors may go open too but I don't know if it applies to this era of electronics. Also what brands/series of caps do you recommend for amps and filters ?

>>1696547
Before that I'd set your DC offset so your waveform is in the middle when you toggle it to ground. As far as "adjust it to 15V PP", doesn't that sound a bit funky when you've got a 1.5V PP waveform? No clue what you're supposed to be doing there.

>>1696547

adjust the position knob so the flat part of the waveform is on the centerline.
right now, the wave is 4 divisions (centimeters) high, and the volts/div knob is showing 0.5V so you have 4x0.5 = 2 Volts peak-peak.
it's possible your probe is doing a 10:1 attenuation, so it's really showing 20Vp-p
google how to change it to 1:1 attenuation.

also, make sure the red knob in the center of the volts/div is all the way clockwise. that's the calibrated position. if it's anyplace else, the voltage will be meaningless.

>>1696556

wait a minute. the text is telling you to use the 10:1 attenuator. that means it will show 1.5V on the screen when it sees 15V. get used to that.

>>1696556
Thanks. Red knobs are all the way over. The sheet says 10:1 probe but I can set it to 1:1 on the probe itself but the waveform goes out of bounds. To be clear I have not adjusted any of these pots prior to the scope so I hope these values aren’t off that badly

>>1696562

ok, 3 divisons at 0.5V is 1.5V --- times 10 means you have 15Vp-p. so, it's ok, next step.

>>1696566
Okay I think I’m getting it now. PP is top bottom waveform distance, each grid is whatever the volts div is, X10 for the 10:1 probe. Cool.
Can do any one of these. Not sure what VIT is but I have an NTSC signal feeding into the vtr right now.

>>1696571

VIT are various test signals injected by some TV stations for troubleshooting. you dont have them, so ignore them. (would be nice to have though.)

>>1696571

VIT are various test signals injected by some TV stations for troubleshooting. you dont have them, so ignore them. (would be nice to have though.)

you have 3 red knobs total. they all have to be fully CCW for the voltage and time readings to be accurate.

>>1696592
Ah ok. All red knobs are fully in their calibrated position. If I move them the red UNCAL light comes on, so we’re good there

>grab 3.5mm socket in KiCAD
>pins are already labelled "T", "R", "S"
>even the 4-pole socket is "T", "R1", "R2", "S"
>find a decent footprint in the footprint browser
>assign them all
>update PCB via schematic
>get error
>pad T not found in footprint
>pad R not found in footprint
>pad S not found in footprint
>no 3.5mm jack symbols with normal 1, 2, 3 labels
why have you done this to me

>>1696595
Somehow this is supposed to be the same

>>1696599
Perhaps zoom out a little time-wise? Where are you triggering? Holdoff may help here, if your scope does it.

>>1696602
I would assume you can get the ntsc signal to show, I have color bars from the generator feeding into the vtr. Notice that all the directions say trigger burst pattern. Do I need a second probe to showing the burst?

>>1695066
Also something interesting to note, those color bars show when i have AFT on (automatic fine tuning) it also shows the grid and dots as it should,
Now, when I turn OFF AFT, the color bars get even weirder, and the grid lines are all over the place.
It seems the AFT circuit is bypassing most of the color correction adjustments. I'll have to look into this.

Dear /ohm/,
I have to power two devices that require 12V DC @ 2A and they both have a female barrel jack connector. I have a single power supply that can deliver 12VC@5A (pic related) and it also has the same barrel jack. In theory, it should be able to power both devices, right?

How do I distribute the power between the two devices? I'm thinking about buying a pack of barrel jacks, soldering some wires onto them and then running them to my devices but I'm not sure how to connect them to the power supply. Do I cut the power supply's connector and just solder two pairs of wires to it? Is there a more elegant solution?

Thanks!

I'm putting together a relay controlled outlet. The plugs I got specified 14 awg wire, but the wire I got said it shouldn't be used for house wiring. Am I fine to use it in this outlet box? Do they just mean don't wire your whole house with it?

>>1696605
>I would assume you can get the ntsc signal to show
I haven't such a source to test on I'm afraid.

>>1696645
Yes, cutting the end off that and splicing two pairs of wires with barrel jacks on them will work, so will making a little box with a socket in one end and two cables coming out of it so you can easily swap out the brick if you break it. Ideally, your wires should be two cores inside circular insulation that's the right diameter to fit well inside the solderable barrel jacks' housings. If not, heat-shrink covers a multitude of sins. You'll want to shrink-wrap any solder connection, so ensure you remember to put it on before soldering the joint.

>>1696655
Should be fine.

>>1696664
>Yes, cutting the end off that and splicing two pairs of wires with barrel jacks on them will work, so will making a little box with a socket in one end and two cables coming out of it so you can easily swap out the brick if you break it. Ideally, your wires should be two cores inside circular insulation that's the right diameter to fit well inside the solderable barrel jacks' housings. If not, heat-shrink covers a multitude of sins. You'll want to shrink-wrap any solder connection, so ensure you remember to put it on before soldering the joint.
Thanks so much anon! After much searching of chinese sites, I came across this: barrel jack to USB. Now, USB is rated for 5V but do you think these cables could handle 12V@2A? I'd then have to make a small distribution box with a female barrel jack and two female USB terminals...

>>1696645

most expeditious way to do this is to cut off all the connectors and join all 3 cables: grounds together, then 12V together. solder is good, but black vinyl tape suffices.
neatest way is to order a Y splitter. for this you gotta make sure to get a M-M-M splitter (which may not exist) or 2 of these in the pic (M-M-F). and you gotta make sure all the sizes match what you need. ''they'' purposely make many diff sizes to ruin your life.
a middle ground is to buy 3 females with wire leads and join like-colored wires.

>>1696655

it's probably speaker wire, or similar, rated for 30V or whatever. that is, the insulation is too thin and too fragile. i'd use proper wire, just to avoid taking the blame in case things go bad. also, 14 seems too small - i'd go for 12, if not 10. just buy a foot at the hardware store, or borrow from the garbage container at a construction site.

>>1696668
>a middle ground is to buy 3 females with wire leads and join like-colored wires.
Thanks anon! I'll investigate further. Maybe I can luck out and find the Y splitter.

BTW, how do I know what AWG wire do I need for 12V@2A?

This is some magical chink led that has only two legs but is rgb and it changes color based on how fast you blink it, how the shit does that work?

>>1696675
https://www.youtube.com/watch?v=gxdgRHmOuIo

>>1696680
Yeah nah, turns out this one is different and just automatically cycles through colors, you cannot pick a color manually
shit i almost ordered them
Chinks never mentioned that at all thank god i read the reviews

>>1696597
wow, that's pretty broken
my initial reaction would be fuck it, use the Connector_Generic 01x03. or wait for the standard footprint library to catch up

>>1696662
you bought such a source. that's where the color bars are coming from

>>1696671
google "ampacity chart"

>>1696599
you're looking at about 2 scan lines there. zoom in on the horizontal time base by a factor of about 10. use the horizontal position to get the back porch of the scan line into view

>>1696668
All right, thanks to this anon, I've solved my power distribution issue with these cables. Took a lot of searching on chinkshit sites but I managed to find the Y-splitter and two cables of sufficient length! Pic relate.
Thanks so much anon!

>>1696666
>>1696668
Search for "DC jack pigtail". Ensure that the jacks have the correct internal pin/hole diameter, since there's two possible sizes for the same barrel outside diameter. One of these is probably much more common than the other.

>SOT-23 is feeling uncomfortably large to me
should I buy jellybeans in SOT-3x3 or continue my regimen of anal stretching?

>>1696682
>you bought such a source. that's where the color bars are coming from
No I'm a different guy who happens to also have a hitachi scope.

>>1696351
>>1696395
>>1696395
I fixed this shit. I'm using a 3.5mm jack splitter and have my headphones plugged to one connector and the other is connected to my computer and it's getting grounded that way. Sweet.

>>1694687
2 x 10nF ceramic from A&B to ground.

no problems; don't introduce code for it that's retarded.

>>1696701
>uses capacitors to debouce
>when there's a micro in the system
stop being a component merchant

Someone put a battery in reverse in a nimh/nicd charger and magic smoke/sparks came out.
What's the most likely culprit for that sort of stuff, capacitors, the LEDs or something else
?

>>1696698
congrats

>>1696710
The part that smoked.

>>1696710
Reverse engineer the circuit diagram, it doesn't look too difficult. And it should be pretty simple to see which component gave up the ghost.

>>1696714
I wasn't there when it blew, so I don't know exactly
It's odd though, there's no darkened area like I expected.
There's a very slight darkening under the lower zener(?) diode next to the IC hole but that's it.
Would the coil/caps blowing even cause visible darkening on the board?

>>1696718
Fair, I figured I'd ask if there's any obvious marks I should be looking for before I go for that, since I usually don't work with busted parts.

>>1696719
Coil is the most suspect part as far as smoking goes if the caps don't look damaged, and the damage could potentially be hidden beneath the wraps, but I can't imagine how the coil would have fried from a measly few volts across it. A few volts in reverse is also not usually enough to pop a cap. Unless it's meant to charge those RC battery packs, in that case anything goes. The diode should be somewhat easy to test, but I doubt it made "smoke/sparks" enough to see outside the case. Diodes would be expected to make a light "pop" and that's it. It's possible that the diode failed along with other parts, so make sure you don't replace a part only to power it on and immediately kill it again thanks to the actual source of the problem being unfixed. Transistors are similar as far as sparks and smoke goes to diodes, but can be somewhat sensitive to negative voltages, so Q1 may well be damaged if anything is.
t. fixed a rice cooker once

>>1696703
>stop being a component merchant
this so much

If something can be done in code with exact the same effect as hw solution would have, then do it in fucking code
because in code you can change it later and don¨t have to solder extra shit do your board
as long as the micro has enough resources and you aren't compromising the needed performance in other areas then using hw is retarded

>>1696710
Is it possible to detect if a battery is connected in reverse?
For example based on resistance

>>1696724
I'll go through them when I'm done reverse engineering it.
Thanks for the advice!

>>1696726
Probably is, but I think it's messy and beyond the scope of cheap chink chargers like this one though.

>>1696726
>>1696728
lmao just use a reverse protection diode

>>1696729
are you retarded?

>>1696730
Yeah that wouldn't work would it, you couldn't charge the thing in the first place. But a simple comparator circuit with a diode and transistor would be able to work if my sleep-deprived skull is still screwed on properly.

>>1696726
Based on voltage. The usual ∆U charger needs a certain minimal positive voltage to start charging. Totally discharged batteries are considered defect and you need to precharge them either using a dumb charger or by other means. Reverse charging is prevented by the design of the contacts.

>>1696119
Does the signal travel through the pads, or is it the lack of a ground plane?

>Dads old Weller didn't work so he fetched the blowtorch

Does a flyback stepdown converter (with 2 transistors and 2 coils on the mains side and 1 coil on the secondary) even make sense?
I've only seen stepup flyback converters, but the output of this one has to be around 5V based on the ratings of the components.

>>1696759
diagram > prose

>>1696761
I haven't cleaned it up yet, so I didn't think it would've been useful.
But it's pretty much exactly that, thanks!

Is there a difference? I have no idea how led strips are laid out

>>1696482
Measured the width of the xtal points in the board, about 12mm. Haven’t got the shield off yet I’ll let you know
>>1696682
So when I turn AFT On I get a better looking waveform, closer to what I should be seeing.

will this led cob will flicker like pic related?

https://www.aliexpress.com/item/4000096787572.html


>>1696763
one is serial, one is parallel. big difference.

>>1696668
>that is, the insulation is too thin and too fragile
Is it just the insulation that's the problem? I only need a couple inches to hook up the plugs and relays

>>1696725
>if the micro has enough resources
which, in this case, amounts to one bit per button, enough space and time for up to 10 more instructions, and the ability to wait a few ms
>inb4 this is a laotian komodo dragon appreciation board, we don't do patience
yep

>>1696766
if you turn off the automatic fine-tune, you have to fine tune the tuner manually, as the manual specified. you should be able to dial in as good a signal with manual titty twisting as with AFT
>12mm
sounds like an HC6 case. so oldskool
the HC49 can be bent to fit, no problem. remember, never touch the body while bending the leads. use a pair of long nose pliers to hold the lead on the body side of the bend then bend the free end with another tool
>shield
just melt and pull (by pushing from that side at the top of the can). it doesn't look like they kicked over the sides, luckily for us

>>1696763
sort of. copper, in wire, foil, or whatever other form, has a low but finite resistance and dissipates power that passes through it. in the case of the LED strip, the upshot is that you might notice LED brightness decreasing as you get further away from the power supply, stronger as the wire cross-section is reduced. that foil on the strip isn't all that thick, you might start to notice the effect after a meter or two if your eyes are good

>>1696777
idk, can't see under the silicone. but based on the lack of a large bulk cap sticking up through it, I think you'll be disappoint. that's the problem with these driverless jobbies: if they don't have to care about flicker, they won't

>>1696799
if you're not working inside the wall, don't worry about it, any 14AWG should be alright

>>1696802
It's basically just an oversized power strip that's computer controlled, so it'll be on a shelf, but I don't want to burn a hole in my greenhouse if I can help it. If I go back for 12 awg do I need to worry about bringing home some with the wrong kind of insulation, or it that standardized?

>>1696800
>but based on the lack of a large bulk cap sticking up through it
gotcha, thanks a lot. i'll look into proper drivers (got pointed towards mean well before) and anon on /homegrowmen/ suggested full spectrum white leds instead of meme purple growlights.
good thing chinkshit isnt that expensive so i can trial various stuff

>>1696804
ah ok
if you keep live terminals 8mm or more away from anything that is conductive but not part of the intended connection, or that is flammable, you should be fine. as always, double-check your connections, make sure they're secure and there are no strands flapping in the breeze. for mains power, take a third look over everything before applying power
>12
the outlet called for 14AWG, though, didn't it? 14AWG is good for 20A, conservatively. stick with that size but get something with better insulation. strip down a spare power cord, if you have to. disaster is expensive and time-consuming

>>1696811
excellent advice from the /out/standing homegrowmen

>>1696811
special bonus link
https://www.engineersedge.com/copper_wire.htm

>>1694686
nearly impossible to do. Conductive ink is how I fix those. They also make conductive epoxy which could be used to glue a thin wire to the trace or to build a pad. Just don't try to solder, won't work.

>>1696812
>the outlet called for 14AWG, though, didn't it? 14AWG is good for 20A
It called for 14 or 12 awg, but I have a 15A fuse on the box so maybe I should stick with 14. I just grabbed what was most convenient, and I didn't think the insulation would be the thing to fuck me.

The inside of the box is pretty full so I'll take your original advice and replace the wire.

>>1696816
thanks, already got that part covered tho. it's good to know people at the local college sometimes.

>>1696763

if the strips are rated at 12V, then, in the top drawing, you need 5x12V or 60V to light them coz they're in series. in the bottom drawing you only need 12V but the supply has to supply more current than the 60V one.

for the series circuit, if you get a constant-current LED supply like the one in the pic, you gotta make sure it can do 60V. the one pictured can do from 32V to 72V, so it would work.

a series circuit is usually preferred coz it uses less wire. but the constant current supplies can be dangerous: you have to match the power rating of the supply to your LEDs. if your supply is rated higher than your LEDs, then all your LEDs can fry.
parallel circuits (bottom drawing) dont care about a supply that's over-rated. like a cat, they just take what they need and leave the rest.

>>1696821

the insulation is not actually the problem. your wire is almost certainly good enough, or you could slip some tubing over it and it would better than fine. that problem is actually optics: when something goes wrong, even if it has nothing to do with the choice of wire, people will start to look for evidence of wrongdoing so blame can be apportioned. by using the standard, official, recognized and certified kind of wire, the blame-throwers have to find something else to bitch about.

>>1696840
I've seen a fair few LED strips, and never once in my life have I seen one that's rated for constant current instead of constant voltage. too dangerous
>series
>parallel
why not both

>>1696841

you've been looking in the wrong places. there's the hobby world where 12V and 24V strips are standard fare, then there's the lighting world, like restaurant lighting, where constant current, higher power circuits are the norm.

>>1696842
circuits, sure, just like street lamps. I can easily imagine that in a commercial or industrial setup it makes good sense to halve the cost of wire. but surely not these flexible tapes?

I know absolutely nothing about electronics. I want to convert an analogue signal from a photoresistor into a 1/0, and have some control over the threshold, how would I go about doing this. A raspberry Pi will be reading the bit.

>>1696881
The rpi doesn't need to control the threshold, I just want to be able to set it. By hand if possible

>>1696881
raspis don't have analog inputs
go ask on the arduino general

>>1696883
Sorry if I wasn't clear, I guess what I want is a 1-bit ADC with a configurable threshold.

>>1696884
Or a circuit that would have the same effect.

>>1696884
oh, a comparator
https://www.mpu51.com/mcucity/appnote/AN-074_LM339%20application%20note.pdf

>>1696887
Yeah I can work with that. Thanks.

>>1696888

you see that resistor in fig.5, Rpull-up. if you dont put that in, it wont work. noobs always miss that; they think it's optional.

>>1696888

you see that resistor in fig.5, Rpull-up. if you dont put that in, it wont work. noobs always miss that; they think it's optional.

the other noob error is to NOT use hysteresis. you wanna add it, like in fig.6 or else you will hate comparators. make it about 10% hysteresis.

>>1696777
>one is serial, one is parallel. big difference.
Wrong

>>1696887
An LM393 would work fine too, or even an LM319 if you're that way inclined.

>>1696902
>noobs always miss that
It's bitten me a few times, that's for sure.
>you wanna add it
Learning how to construct my own arbitrary positive and negative feedback loops has vastly improved the quality of circuits I can make.

>>1696931
thanks. I keep forgetting that noobs don't into parametric selectors
>constructing feedback loops
I bet it also gave you a much broader understanding of how things work, man-made and possibly otherwise. there are twentysomethings today who do not understand how a thermostat works

>>1696934
Why did the thermostat blush?
Because it saw the bimetallic strip!

On an oscilloscope probes, the attenuation switch many probes have does not "divide" the voltages by the number does it? Like having it in x1 reading a signal with a 50v wont suddenly turn into a 5v reading after switching to x10 attenuation (I was under the impression it was this way to increase the Vpk limits your scope could read, seems it doesnt).

What it does do is add impedance for "finer" measurements doesnt it? Sorry for dumb question, im new to this and dont want to fuck up.

>>1696840
>that problem is actually optics
Thanks for clarifying. I'll still replace it on the off chance that there's a fire (related or otherwise) and it costs me the insurance coverage or lands me with criminal charges.

>>1696939

>>1696840
>coz they're in series
No they aren't. Series would mean they were connected black-to red, black to red, etc. But they're instead connected red to red, black to black, etc.
They're just two different ways of wiring them in parallel.

>crystal-less USB 12Mbps
>32kB flash
>TSSOP20
>$0.88 each in single quantities
how will FTDI ever recover?

>>1696965
the resistance of the copper foil on those strips is significant. at that level of structure, it's reasonable to look at it as a component in a series connection

>>1696945
it's BOTH
it sure does divide the voltage. when you measure 50v with a 10x probe you will measure a 5v signal.
It does this BY adding impedance. The impedance it adds forms a voltage divider with the scope's input impedance.
and yes you do increase the voltage limit your scope can read with this, why wouldn't it?

>>1696992
But it isn't, each strip has red-black labels on it. Not to mention all the +ve rails are at the bottom and all the -ve rails are at the top, and the fact that both power inputs go to the first LED strip, and not one to the first and one to the last. Think for a minute, it's impossible for that to represent series LED strips.

Manhattan, here we come!

>>1697029
I repeat: at that level of structure
it is a series connection, which is not the same as a series circuit, nor does it need to be. look at it from the perspective of the copper, not the LEDs

>>1696840
>if the strips are rated at 12V, then, in the top drawing, you need 5x12V or 60V to light them coz they're in series.

but they aren't electrically in series, only mechanically

>>1696800
Look at the size of that guy. About 17mm wide

>>1696026
ya it's more for like the back of an enclosure to replace easily without opening the whole thing up

>>1697035
Oh. But the guy I replied to was saying he needed 5*12V = 60V to power the thing, why would you defend that?

>>1697096
>there are only two sides to every argument

>>1697057
yep, it's a big 'un

>>1697242
indeed. ill be careful when bending the leads on my new one when it comes in

If I run a 20-150 hz signal into a power amplifier, will I get a noticably stronger output signal than if I ran a full range input signal and then used a low-pass filter?
I mean, the amp has limited power, so if it focusses all that power into the low frequency range, the output should be bigger, but will it be noticable on a subwoofer chassis that does 85 dB at 1W?

We're talking ~15W of amplification here.

>>1697293
filters simply dissipate power on a frequency-dependent basis. you're simply choosing where to dissipate that power: in a pissant RC or LC or active filter at the small-signal level, OR in capacitors, inductors, and/or your speakers at the power level
if you don't notice some improved clarity in the sub-bass by filtering before the amp instead of after, you'll definitely notice it in your wallet

>>1697293
It depends upon a) the amplifier and b) the filter. Applying the filter to the input will never be any worse than applying it the output; it may or may not be better.

>>1697298
>>1697301
Well, I don't really have a choice. I'm running from the subwoofer pre-out of my car head unit to a tiny power amp and then into the subwoofer driver. There is no space for an additional filter or a larger amp in the car anyways.
I just wanted to know if 15W with limited range input would give me more bass than 15W at full range with filter after amp.
Then again the difference would only be a few watts, 5 at most, most likely not noticable.

>>1694516

What the fuck this shit is ?
Laundry machine refuses to turn on, and there's this crack

>>1697303
>no space
you sure?
a 1/3 reduction is a little more than 1.5dB if my math is correct, you would have to make the call on whether that's noticeable

>>1697031
Good old LM324

>>1697310

the crack is nothing. it's just the ceramic casing; the actual resistor is likely 100% good.

try knocking on the relays (big white cubes) with the handle of a small screwdriver as you activate the machine. old relays can sometimes lose their strength.

>>1697462
dash ageisht

What's the point of the diode in this circuit? I tried simulating it with and without the part and I get 4.5 volts in either case. Some kind of filtering? The input voltage is DC.

>>1696818
I figured. Already got myself a board with a decent pcb, much easier to cut some of those traces

>>1694516
I'm trying to design a vcf here and this is what I have so far. The varactor is 4pF at 0 volts but I'm not seeing any results when changing the voltage to it. Did I do something wrong or do I just need to add more filter stages and get a sharper cut off? Any help, feedback or resources would be really appreciated thanks.

>>1697481

prevents harm to cap in the event you plug in the battery backwards, trying to emulate Electroboom.

>>1697503
integrator action is the result I'd expect when filtering 100x the corner frequency
also, the dc blocking cap is usually much larger than the varactor capacitance so that the varactor dominates

>>1697503
>>1697544
Yeah set that DC blocking cap to 100pF at least.

>>1697544
>>1697550

Ok so I upped the capacitance on the DC cap to the recommended 100pF. I tested the circuit as pictured with 1 and 4 pf caps and got the expected/desired filtering where 4pf had a lower cut off than 1pf. When I tried the varicap at .01V applied I still got the same integrating behavior as if it was going straight to ground, even though I would expect it to be similar to the 4pf cap.

At this point it seems like there must be some error in the way I'm wiring the varicap. Thanks for the help so far

>>1697646
0.05V isn't very high, those things usually have a preferred bias voltage range from 2V-15V or so. Also I think you need to put a resistor in series with the bias voltage source, otherwise you're basically grounding the signal to a power rail, when in reality it should have somewhat of a low-pass effect in conjunction with the varactor. Hence ensure that the operating frequency is significantly higher than this "filter's" cutoff frequency. There may also be a high-pass filter from the 100pF cap and this new resistor to a rail, whose cutoff frequency may need to be equal to or less than the operational frequency.

I'm a total beginner and have dived straight into a club at my school that's working on a project using this: https://www.st.com/en/evaluation-tools/nucleo-f446re.html . I'm kind of confused on what exactly this is, mainly because it mentions Arduino, and the schematics have pins labeled "Arduino Connector" as well as "Morpho Connector". What's the relation here? I thought Arduino was an entire board itself? It kind of looks like this is an Adruino + some other stuff.

I'd ask other members but it's both 1am and I don't want to seem like a total dumbass right off the bat with a question like this.

>>1697516

Thanks, I'm a dummy for not thinking that.

>>1697660
Arduino is a development environment, referring mainly to the software that's effectively an IDE atop AVRDUDE, which is software used to program AVR microcontrollers. Though I believe there may be exceptions to this rule; microcontrollers that you can program without AVRDUDE or ones that aren't in the AVR family at all. A large variety of boards are made that are Arduino compatible, by the Arduino company, by other reputable companies like Robotdyn, and by noname chinese manufacturers. These boards typically just have an ATMega328 on them (e.g. Nano, Uno, Pro Mini), but the Arduino environment supports a variety of other MCU models (e.g. ATMega32 on the Pro Micro, ATMega2560 on the Mega), and even more if you include third-party addons (e.g. ATTiny85 on the Digispark). These boards are commonly referred to as Arduinos. I'm unsure where STM32s sit, but they're a pretty common MCU family these days, so I imagine they can be worked with using the Arduino environment.

Something to note is that the common Arduino boards have USB sockets and their own USB-to-serial converter IC that lets you program them directly through USB, but some less common boards require other methods of programming. I think the Pro Micro's microcontroller is USB compatible without the need of an extra IC. ICSP (in circuit serial programming) is a more common method outside of hobbyist fields, and this can be done with a device like an avrisp, or just with a specially programmed Arduino Uno. Your board looks like it has a USB input, so I wouldn't worry about that for now, though it does look to be split into two sections. I imagine the side with the USB can be used as a programmer specially for the other part of the dev-board, acting like an Uno in the previous example. Whether or not you can replace it with an Uno or avrisp is unknown, but it's somewhat likely.

I imagine their "morpho connector" is just a proprietary name for their sizeable GPIO setup.

How do i solder a wire to an aluminium tape? i tried to cover it with oil like i saw on tutorials but i amhaving zero luck

>>1697707
Sand it before using oil or rosin as flux? Sand it while using oil or rosin as flux?

I want to recycle some 18650 cells to power a Raspberry pi (+ screen and periphals).
I realize that I want a board to do the heavy lifting for me, so pic related are two I found. (1) is one you can get cheap from china, but it's only rated for 1 amp, and a Rpi can take up to 2.5 A from what I heard.
(2) is more expensive, but is rated for 2.1A which sounds better. Is that going to be okay? If not where do I find boards that are rated for that? What do I need to look at other than voltage, current and interface?

Lastly, they seem to assume one battery attached. If I wanted a higher capacity, can I just add more Li-ion cells in parallel?

>>1697550
it's a sim, he may as well set it to 100µF

>>1697774
look for "raspberry pi battery hat"
or look for a power bank that specifically notes pass-through charging capability
>more cells
no, Li+ electrical characteristics vary based on their life history. never connect used cells in parallel if they are at different voltages or have ever been used outside of that parallel connection
a reminder that playing with Li batteries is literally playing with fire. put your wet dream on pause until you have read everything about Li-ion batteries on batteryuniversity and gained an appropriate respect for the concentrations and rates of energy that make Li batteries worth using

>>1697655
Hey man, I made your changes. The bias voltage is now much higher now at 3V. I increased the resistance at the bias such that the cut off frequency of the high pass filter of 100MO and 100pF is now less then the operational frequency. I'm still seeing the undesired behavior though so I might try another sim tool in case this one is buggy and also begin working on an alternative which will just use jfets to control the cutoff freq. If I find anything new I'll post it. Pic related is current progress. Thank you for your feedback and help.

>>1697705
Thanks anon, that makes it a bit more understandable.

>>1697788
>100µF
I'd be worried that he'd get that long capacitor ramp messing up his sim, but for a continuous sim I guess that doesn't matter as much.

>>1697031
everyfucking time I try this I just hear "pop" and the copper flakes off from the board reee

>>1698062
That's a piece of copper-clad FR-4, not copper tape. I don't see the copper clad being any more vulnerable than an SMT PCB, sure you're not running your iron too hot?

>>1697788
Once they've been roughly balanced to same open circuit voltage connecting li-ions of same chemistry in parallel is fine, forcing them to same voltage by paralleling keeps them in balance despite the different capacities.

>>1698302
This, just connect them with a 10Ω resistor to balance them out and then you can connect them properly afterwards. There's nothing wrong with having a 1Ah cell in parallel with a 2Ah cell, since that's basically the same thing as having three 1Ah cells in parallel. But I'm unsure if there are differences in chemistry that might lead to significantly different forward voltages and/or disparate charging curves. Considering that charging circuits like the TP4056 seem to be used with every lithium ion and lipo under the sun, I'm guessing it's not an issue.

I have a device powered from a buck converter, but if i connect for example a battery across the buck converter output pins as a secondary power source, the buck starts getting super hot, any idea why?
the input power to the buck is disconnected

>>1698351
aaand it also apparently fried my IC.. thanks alot buck, you fag