/diy/ - Do It Yourself

Old thread reached bump limit.

>>1151071

How do you clock a 74 series serial to parallel chip with a micro?

>>1158755
>how do I use google?
like this:

https://www.google.nl/search?q=hc595&safe=off&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiFuovJ25fTAhWhAMAKHedGBboQ_AUIBigB&biw=1661&bih=728#imgrc=_

I have a hard time actually putting circuit diagrams onto a physical breadboard
Is there some way to visualize what goes where better?

>>1158761
Well, the spacing for breadboards should be 0.1 inches apart from one another. The spaces in the middle are 0.3 inches apart. You can layout your circuit using EAGLE, and turn on the grid for 0.1 inch spacing. If you're running out of space on a breadboard, think about buying some more. Protoboard sucks, and you'll eventually want to start milling PCBs for prototypes using a CNC machine like the Othermill

>>1158755
a micro what?
micro brain?
micro penis?
no idea i don't have experience of either.

>>1158773
Don't come here if you know shit and want to know shit. And don't answer questions not addressed to you faggot. Fucking kill yourself already.

>>1158755
You would use the GPIO (General Purpose Input Output) pins of a microcontroller (like arduino, raspberry pi). You would raise the pin connected to the 74 series chip high then low. Most 74 series chips have fast clock speeds, so you shouldn't have to have a delay between the raising and lowering of the pin.

babby's first pcb: isolated usb to uart for uc debugging.

i have crippling autism and it tickled me to put the ground plane on top. maybe i'll put a meme on the bottom copper.

>>1158794
got any schematics? Those traces look slick

>>1158795
the tx line is run off power scavenged from the photovoltaic coupler and the rx line. it's limited to ~40uA average sourced when there's no rx activity but should be able to drive the line capacitance anyway as the slow response time of the photovoltaic limits it to <10kbaud. for all that idiocy i get one less pin on the header.

>1158599

thanks for the tips. the data sheet says 20mA @ 2.2V so I mathed it and it comes out to 110ohm. I don't understand resistor values, but I have heard they don't come in every single value, so I just used a chart called E12 and chose the next highest value.

here's the datasheet for the LED.

>>1158599

thanks for the tips. the data sheet says 20mA @ 2.2V so I mathed it and it comes out to 110ohm. I don't understand resistor values, but I have heard they don't come in every single value, so I just used a chart called E12 and chose the next highest value.

here's the datasheet for the LED.

>>1158872
fuck me I fucked up this post like 3 times.

>>1158871
>>1158872
>>1158874

>>1158877
nobully

>>1158872
>20mA @ 2.2V so I mathed it and it comes out to 110ohm

You are starting with 9V.
2V are dropped across the LED (1.8v-2.2v)
This leaves 7V to drop across the resistor @ 20ma
7v / 20ma = 350Ω
Standard values near this for 10% resistors are 330Ω (21ma) and 390Ω (18ma) - either will be OK

Ok all those guys from the previous thread saying you can get a voltage difference of 24V from a 12V battery just by using an amplifier are full of shit. The whole "I have a voltage difference of 12V after each of the two amplifiers, so they add to 24V" is like trying to take two 12V pairs of wires from a battery in parallel and adding them in series to get 24V. It doesn't work.

As you can infer from pic related, by using the two opamps you essentially double the gain, but the signal can never reach an amplitude above 6V, just the same as changing the gain on a normal opamp.

>>1158987
FFS, how about actually reading what people are trying to tell you.

Or just give up on electronics, because it's obviously too complicated for you.

>>1158987

>>1158975
well good thing I didn't actually do this circuit with my breadboard then.

Is there any such thing as an "active resistor"?

>>1159056
Like a voltage controlled current source?

You could use a MOSFET.

>>1159010
Oh hey is that a way to multiply voltages using only transistors and resistors? I guess I was just being ridiculous and all power supplies do this because of its extreme simplicity and this doesn't work by adding sine waves on top of one another that would in reality be coming from a parallel voltage source, thanks anon.

>>1158794
Longchip is long

>>1159056
Depends on what you mean, but you could try googling "active load". There are both test instruments and circuit blocks under that name, both used to replace resistors.
You can also use FETs (junction and MOS) as adjustable resistors and as such to replace potentiometers etc. in some applications. This use is slightly different than active load use (which is also possible with FETs).

>>1159010
Ok sarcasm aside that sort of makes sense by adding two waveforms 180° phase shifted, but you'd need something to shift that. I didn't think an inverting amplifier could act that way, but I guess it can.

While fixing up the busted headers on this chink color sensor and checking if all connections were working, I noticed there seems to be a 0 ohm pulldown resistor on the OE pin.
It's more or less this sensor https://www.dfrobot.com/wiki/index.php/TCS3200_Color_Sensor_(SKU:SEN0101)
That doesn't seem quite right to me, or am I missing something?

>>1159145

the resistors probably aren't necessary anymore. maybe a newer revision of the sensor or something. It's not all that rare to come across, so I wouldn't worry about it.

cheaper to just use a 0 ohm resistor rather than throw out all PCB's they made up prior to the change. PCB's are several times more expensive than a couple of resistors.

because the 0 ohm resistors are in a surface mount package, they can easily be fed into a pick-and-place assembly machine.

>>1159145
>that GND pin
That's some nice soldering there, quality part.

>>1159106
> Oh hey is that a way to multiply voltages using only transistors and resistors?
It's a "full bridge". By itself, it doesn't multiply voltages, only the voltage swing (i.e. you get -X to +X where X is the supply voltage). But you could drive a diode-capacitor voltage multiplier from it.

Charge-pump voltage doublers (like in the MAX232) drive a voltage doubler from a half-bridge; that gives you an increased voltage with one side referenced to ground, which tends to be more useful.

>>1159184
I get the gist of it, but inverting amplifiers and H-bridges are kinda confusing. Haven't learnt them formally in physics lectures yet, but I did end up making the lecturer have to explain what the "magic smoke" was to the rest of the class in a lecture about CW multipliers.

I honestly learn half the theoretical stuff covered in the course through a little experimentation and a bunch of contributing on /ohm/, I really like this place.

hi ohm i dont know much about electronics, other than how to follow a diagram but several months ago someone helped walk me through a dc wall adapter so i could make an etcher for my knives.

would this be safe to use on an electronic cigarette? i dont want to sent 12v into the battery and im not sure if this setup would. im guessing if i turned it off it should be safe but i dont know and i cant get the battery out.

please excuse my ignorance and shitty ms paint.

Hey guys I was thinking of getting weller wlc100.
>https://www.amazon.com/Weller-WLC100-40-Watt-Soldering-Station/dp/B000AS28UC/ref=sr_1_3?s=hi&ie=UTF8&qid=1491856546&sr=1-3&keywords=stahl+soldering+station

and I came across
>pic related
>https://www.amazon.com/Stahl-Tools-SSVT-Temperature-Soldering/dp/B0029N70WM/ref=sr_1_1?s=hi&ie=UTF8&qid=1491856546&sr=1-1&keywords=stahl+soldering+station

/diy/ have any experience with either one?

>>1159239
The DC power there wouldn't even be 12V, it's probably higher but depends on the load. AC is measured in RMS value, the average absolute value of the voltage. RMS = peak_voltage / sqrt(2). When you put a filter capacitor across the DC outputs, the capacitor charges up to the peak voltage and holds on to it depending on the current drain. In the extremes, if there is no/minuscule current drain then the average output voltage will always stay buffered by the cap and be the same as the peak output voltage, so about 17V, but If you pull a huge drain on it then the cap will discharge very quickly and essentially follow the rectified AC waveform, making the RMS voltage 12V. The bigger the cap, the less ripple-voltage.

A few equations for you:
max_voltage = RMS_voltage*sqrt(2)
ripple_voltage ≈ max_voltage/(2*load_resistance*capacitance*frequency)
ripple_voltage ≈ current_drawn/(2*frequency*capacitance)
effective_DC_voltage = max_voltage - ripple_voltage/2

I recommend choosing a capacitor based off what ripple_voltage you can withstand, by rearranging the ripple_voltage equation:
capacitance > current_drawn/(2*ripple_voltage*frequency)

Theoretically as long as the current across the 18650 is in moderation the voltage can be as high as reasonable, I have seen a circuit whereby a NiCd was charged by rectified mains voltage with a big enough dropper-resistor. But you'll have to be more careful with a Li-ion, they have a habit of exploding. If the box shown is some sort of prebuilt Li-ion charger circuit that's made to be able to work off 17VDC or 12VAC then you're fine, but otherwise I don't know what your circuit is. Why have an AC/DC switch? What are you trying to accomplish?

>>1159408
i understand that the voltage may not be exactly 12V but that's what the charger said so that's what i figured i would label it as, it already came with the diodes and capacitor i just had to solder on the leads to the double switch. none of that can be changed.

normally i just attach the positive clip to a knife or tool i want to etch and press the negitive where i want to etch through a stencil, then switch to ac to make it black.

im trying to not put voltage to the battery, im simply trying to etch my name and some art into an electronic cigarette without blowing it up. the negative of the battery goes through the casing though and im wondering if i left it "off" would it affect the battery in any way? as far as i know it should not even notice the battery and just go through the etch pad and the connecting lead but i'm not sure and it could explode if im wrong.

>>1159400

you should decide on the basis of, "Do i wanna spend double and get an iron that'll work just fine in 15 years, and always have replacement tips available, or a chink clone that'll come apart in 2 years."

if you read the reviews, you'll see what i mean.

>>1159414

none of the electricity is gonna leak inside the unit unless you make a specific connection to something that's inside.

i never realized that Ac and Dc etch differently. in fact, i'm not sure i believe you when you say so. i'll have to try it myself. all i recall is that AC is a lot more sparkly.

>>1159427
ya ac seems to etch like if you have dc set up backwards if you aren't quick or if the knife is small(i guess that's due to resistance and higher current as a result?). either way i usually do 3 dc passes and use ac for a 4th, it seems to come out darker for me, not sure why and no guarantees it will work.

thanks though it will be fun to watch if this blows up on me i guess.

>>1158696

I know how to calculate voltage in a circuit with only resistors now what?

>>1159414
The AC might be a problem for leaking through the housing, but at that voltage and frequency it would only affect particularly delicate electronics. You know, capacitance or something. If possible I'd remove the electronics from the housing, either way the battery won't be the component that's effected by the current.

>>1159453
unfortunately it's all a sealed unit. so thats a no go. all thats on it as far as im aware is a low voltage cutoff and over current protection chips along with a few leds. just realised im an idot however and forgot that i can remove the resistor (coil, head) and essentially break the positive side of the circuit, this should almost definitely keep the unit safe.

>>1159445
the only way to learn electronics beyond the basics is to think of something you want to make, and start reading about the different circuits and theories needed to make it.

>>1159458
If the switch is closed then that won't be an issue anyways, I'm just wondering whether the capacitance of the ground might cause some voltages appearing here and there, probably because of ground loops. Like how you can get a shock by touching the mains live terminal without completing a circuit. I'm personally surprised that this thing isn't user-serviceable, does it use torx or something?

>>1159239
>>1159414
>>1159443
>>1159458

Just mark the fuckin' thing and go on.
If it damages it - don't mark the replacement.
FWIW: It won't affect the unit.

>>1159425
I went with weller anyways.

>>1158696
What is the go to entry level oscilloscope now a days? I know that the Rigol DSO 1052e was commonly recommended in the past, but a good amount of time has passed.

>>1159577
ds1052z or 4z

that siglent dave jones reviewed had a better bandwidth and lower target price but i don't think it's released yet

>>1159597
sorry i think i bridged universes, i can't find any record of a 1052z. i forget what their 2 channel model is. if you're not poor you'd might as well get the 4 channel anyway, i've needed all 4 before.

>>1159577
To add to his question, are there any good software-scopes for sale? Technically they should be cheaper since they don't need all their processing hard-wired, a decent processor in them, or any displays or knobs, just a way of sending their data to the computer, but I've noticed them being particularly pricy. Is this because the software is megabux, or is it still an emerging tech? There better be one that isn't Windows exclusive either, even if I do have to shell out a few arms and legs of the family.

>>1159171
But this way if I try to make the OE pin high it would just directly short to ground, wouldn't it?

>>1152374
>all of these can be had in packs of 10-100 for $1-2

I bought the lab book for AoE, and it suggests buying eg. LM317's from Digikey at a price of $2.5 per piece. Are they higher quality or is it just a huge ripoff?

>>1159755
Yeah I'm wondering too where one would get components that cheap. The regular legit channels don't sell them for anywhere near those prices. For lots of those components not even aliexpress is that cheap.

Does anyone have a recommendation for an electrolytic capacitor kit that has several common values in it that isn't too much but still contains good quality capacitors?

>>1159755

try ebay

Anyone else using LTSpice on MacOS? The Windows version updated a week ago, while the MacOS version updated 190 days ago, and the updater shits itself when I run it. Are there any new features I'm missing?

>>1159996

> MacOS
> windows

bullshit babylon OS

If I wanted to light that LED without a resistor how much wire would I need?

>>1160015
>how much wire would I need?

what gauge?
what material?

>>1160015
The equivalent length of nichrome wire. You can get them with 70 ohms/ft, so from 1 ft to 100000ft depending on your power supply

>>1160015
Visit the wikipedia page for American Wire Gauge, it states the ohms/metre and ohms/foot for all of the wire gauges. Dropper resistance value is (source_voltage - LED_forward_voltage) / LED_forward_current.

Say you're using 32Ga copper wire, which has 0.538Ω/m, a 9V battery, and a 3V, 50mA LED. Your resistance will need to be 120Ω, so you'll need a little over 200m of wire. With 40Ga wire you'll need 35m, which is still stupid. You'll definitely need proper resistance wire, but you could always try making your own carbon resistors by burning bamboo fibres in a low-oxygen environment. Oh and just for shits, you'll need 234km of 2Ga wire.

Now if you head on over to the wikipedia page for nichrome you can look into making a reliable resistor for yourself. Nichrome has about 1µΩm of resistivity, which you divide by the cross-sectional area of your wire to get the resistance-per-distance. 32Ga gives 31.25Ω/m, so you'll need nearly 4 metres of that. 40Ga gives 199Ω/m, so you'll need only 60cm of it. You could (and should) wind this up to make it compact and prevent it from snapping, but who wants all that extra inductance?

Nichrome isn't a particularly good material for high-impedance resistors. If you want to make a resistor, use water and adjust the salt content until you're both getting a reasonable brightness from the LED, and not enough chlorine gas to make you cough up blood. If you just want to use an LED without waiting for the resistor to arrive from digikey, tough luck, build the salt-water corrosion machine or shell out the cash for fast shipping. If you want to demonstrate resistance-per-distance, 40Ga nichrome will be pretty damn brittle and hard to clamp clips on to, so you should probably buy one of those slide-rheostats they have in physics classrooms.

>>1159408
>RMS is the average absolute value
you are either wrong or your phrasing is just shit

hey /ohm/
powersupplyfag here
So I think i'm going to transformer > bridge rectifier > caps > switching preregulator for my power supply.
2x0-15V taps on the toroidal transfomrer i ordered off ebay
I'm going to be using the LM78S40 I think (it's the only switching regulator i can find at the local shop)
My question is, since 15VAC + 15VAC = 30V x 1.414 = ~42V at the capacitor filter and assuming it can get as high as say 45V.. how do i protect my p channel mosfet? the regulator will drag the gate to ground which means it'd be 40 Vgs when its under light load which would probably destroy the mosfet?

>>1159725
Scopes _need_ some kind of hardware acquisition and triggering circuitry to be useful for non-trivial applications. That's where most of the cost is, and you can't get rid of that portion.

>>1159755
For stuff that's old and not special, like a LM317, you can probably get away with buying from eBay since there's loads of old stock out there.

Would a simple AD9833 module work for making baby's first signal generator?

>>1160136
Jolly good, old chap. You need something else to control it of course.

>>1160139
Yeah, I got enough parts for that lying around.

>>1160117
Ok that's supposed to be an "of" instead of a ",", I was just emphasising that it's the average value with respect to magnitude, because averaging a sine wave would otherwise result in a zero. Oops.

>>1159725

There is far more competition and volume for normal scopes. The higher end USB scopes are boutique equipment.

Only on the low end (~20 MHz) are the USB scopes cheap.

>>1160195
That wasn't really the problem. If you average the absolute value of a sine, the result is about 90% of its RMS value.
RMS = root mean square, meaning that you square the voltage before averaging and then take a square root of the result.

>>1160124
An easy option would be to use a high side mosfet driver IC (and optionally replace the P-fet with an N-fet).
You can also try something like pic related, but you need rather small resistors to avoid excessively long turn-off/on times.

Achieved a milestone today: I blew up my first component.
Hooked up a photocoupler directly to a power source, completely forgetting that inside is in fact an LED.

I have a device here that gets powered by usb, but i want to connect it to the wall outlet, i found a guy on some forum that says that it takes 3v and 500mAh, is there a way to verify this? If i connect a power supply that's for example, 4.5V and 600mAh, will the device just take what it needs of it will be overcharged (and possibly get damaged)?

>>1160364
If it's USB powered, why doesn't it take 5v?

>>1160375
I don't, it's what the guy said, the device is a Turtle Beach DSS.

>>1160376
And you just want to just it through the MiniUSB socket? Then it takes 5v.

>>1160380
*use

I've got a 2.4 GHz RF transceivers but it's in a bad location, would putting the antenna on a 2m shielded cable affect the signal at all?

>>1160380
Yes, that's logical, but the guy said 3v so idk, that basically leads to my second question, in terms of Amps, does it take what it needs or is it forced to use what the power supply outputs?

>>1160401
it "takes what it needs"

>>1160404
Thanks man

How do I learn how to do pcb-design?
For example if I want to design a board or a SoC (akin to raspberries and such), how do I do that?
What resources are there?
What will I need to have?

Dunno if this is the right place to ask but whatevs.

Is the result of programming PID logic in a microcontroller, reliable? Also, is there an easier way to do that? Someone told me to just use a PID controller, but I need it the controller to do other things too, like store results among other things.

Sorry for not explaining myself better, I'm new at this stuff.

How do I learn how to do pcb-design?
For example if I want to design a board for a SoC (akin to raspberries and such), how do I do that?
What resources are there?
What will I need to have?

>>1159180
>implying the other joints are any better

>>1160207
if I replace p-fet with n-fet, i'd probably need to despec and make it like 24V max instead of my originally desired 30V ;-;
yeah i thought of a simple resistor divider too but dunno if that's the best idea. with a 2/3 divider, i can get about 30V which is 45 - 30 = 15, close to the 20Vgs max. Dunno how bad that is. and then if its as low as 30V in, then its 20V which is 10Vgs which is ok? i dunno how ill advised that is. and yeah the resistors divider I was thinking of using is like 20mA, which on such high voltage would dissipate about 2W total or so. Thoughts?
Also your schematic is basically what the regulator does already, with the N-channel mosfet substituted for the regulator IC darlington

>>1160447
2/3 divider using three 470ohm 1W resistors* i should've said

>>1160437
It can be just as reliable as any other microcontroller-based design, meaning sufficiently reliable for normal use.
You can implement a PID controller (or a P or PI controller) using analog techniques. It isn't even particularly difficult, but trimming analog PID controllers tend to be more tedious.

>>1160447
>if I replace p-fet with n-fet, i'd probably need to despec and make it like 24V max
Why?
>simple resistor divider
One of the key components of that circuit was the 15V zener diode. If you dimension the resistors properly, 30-40V input voltage range is no problem.
> I was thinking of using is like 20mA, which on such high voltage would dissipate about 2W total or so.
Depends on how big the mosfet is and what is your switching frequency. Big mosfets have high gate capacitances and high switching frequency requires fast switching.
>Also your schematic is basically what the regulator does already
Of course. The regulator requires a high side switch and the presented circuit is a high side switch.

>>1160460
>Of course. The regulator requires a high side switch and the presented circuit is a high side switch.
Well I was getting more at the fact that the n-channel mosfet + control circuitry stands in as the regulator IC. I'm using an external mosfet pchannel mosfet (or plan to) so i can switch higher currents

>Depends on how big the mosfet is and what is your switching frequency. Big mosfets have high gate capacitances and high switching frequency requires fast switching.
i've looked at the datasheets and Ciss is about 2k pf on some of them. little higher or alittle lower.
>One of the key components of that circuit was the 15V zener diode. If you dimension the resistors properly, 30-40V input voltage range is no problem.
I'm not totally read up on parallel resistors with zeners. so not sure how that all works out. Aren't zeners a little slow for tens of kHz switching?

>if I replace p-fet with n-fet, i'd probably need to despec and make it like 24V max
Why?
because at high load, i'm going to just assume the transformer outputs enough voltage and current to sustain 30VDC across the filter caps. If i want 30VDC on the source of the mosfet, Vgs needs to be 30+10 = 40V. I've heard of the bootstrapping thing with optoisolators and I don't think that's fast enough iirc

>>1160136
I was under the impression that the "baby's first" signal generator was just a 556 and some filters.

>>1160201
Well that makes a heck of a lot of sense.

I'm a noob wanting to learn fpgas. I have some crazy ideas for an open hardware computer. Would this work?
>single Lattice ice40hx8k, I wonder if there are enough cells.
from github:
>RISC-V RV32E ORCA soft core
from opencores.org:
>vga character display
>ps/2 keyboard
>ethernet interface
>sd card
hardware:
>640x480 vga monitor
>ps/2 keyboard
>breadboards, power etc. pcb and laptop form factor eventually
software:
seL4+SOS has been ported to RISC-V. Basically want shell, compiler and networking tools. Very old linux or bsd could be an option. IDK.

Do all DC bench top power supplies/diy power supply circuits have filter capacitors across their outputs? I'm wanting to mess about with LCR circuits and don't want any external capacitance mess with my readings, but I still need the output voltage to be at most 5% ripple, preferably lower.

>>1160540
>Do all DC bench top power supplies/diy power supply circuits have filter capacitors across their outputs?

are you joking, nigger? you cant do without 'em.

>>1160520
>Well I was getting more at the fact that the n-channel mosfet + control circuitry stands in as the regulator IC
Oh, that. Yeah, sure, you can use the internal switch of your switcher IC, if it can handle the required voltage. 78S40's switch is rated for 40V only, though.
>2nF gate capacitance
I'd use a mosfet driver IC in that case. Or at least something bit fancier than that resistor + zener contraption.
>Aren't zeners a little slow for tens of kHz switching?
No. Big low voltage zeners can have lots of capacitance, though.
>I've heard of the bootstrapping thing with optoisolators and I don't think that's fast enough iirc
If you're referring to those photovoltaic optos then yes, they're slow. They aren't your only option, though. You can use dedicated high side N-fet driver ICs (or build an equivalent from discretes) or use an auxiliary power supply for the gate driver.

>>1160136
>>1160532
My babby's first used 8038. It was a garbage tier signal generator, but at least it was better than anything using 555.
Apparently eBay's Chinamen sell kits based on 8038 at $3 or so.

That said, it's 2017 now. NCOs are a valid option.

>>1160540
Usually they have, but it is possible to design PSUs without any capacitors at their output. Any regulated power supply still has nearly zero effective output impedance, so removing the capacitor isn't going to help you much.

>>1160546
>Oh, that. Yeah, sure, you can use the internal switch of your switcher IC, if it can handle the required voltage. 78S40's switch is rated for 40V only, though.
Yes, I think I'm going to have to LM317 the 78S40 IC to run off less than 30V. Because if the filter caps give 30V, the LM317 needs at least 3V overhead which means 27V. I can't actually tell what Vdd actually limits on the chip though. I could hypothetically run it with 12V no?

>I'd use a mosfet driver IC in that case. Or at least something bit fancier than that resistor + zener contraption.
>mosfet driver IC Is that really necessary? I can't find a mosfet driver IC locally at all.
>zener capacitance
Dunno what to take out of that. Slower gate discharge?
>dedicated high side N-fet driver ICs (or build an equivalent)
Don't know of any of those ICs.
>discretes
wouldn't that involve making a section that sustainsup to 40VDC? With a tracking preregulator, the source of the mosfet could hypothetically be as low as 5VDC as it tracks a 0 - 1VDC on the final output no? Which would mean I'd want Vgs to be 15V above ground? Whereas if I am outputting 30V i'd need 40V above ground?

>>1160554
The first page of the datasheet says the minimum supply voltage is 2.5V.
There are also an application circuits for higher currents, using external (bipolar) transistors.

>Slower gate discharge?
Charging too.

>Don't know of any of those ICs.
You could just google "mosfet driver". There are plenty of those, from several manufacturers.

Pic related is one popular way to drive high-side N-fets. In your case VCC would be 40V and the D1 supply would come from a 12V (or so) supply instead of VCC. There are also ICs using the same basic idea, except that they are faster.
Another option would be to use a fully floating power supply for gate driver.

>>1160599
>minimum voltage is 2.5V
I just don't know what i can or can't do with lower supply voltage is all
and yeah I saw the application with external pnp bjt

>Mosfet driver IC
I feel like these are hard to find at least locally. Can't find shit
ebay gives me some options but waiting like a month for it to come from china to test.

I also looked up how to figure out how much transformer voltage drops under load. found some new stuff, but nothing I know how to test easily yet.

I'm already dealing with op amp oscillation on the output of an LM317 when there's a capacitor pretty much anywhere on it -_-

>>1160533
My guess would be it's not big enough but you should just try synthesizing etc and see what you can fit.

>>1160444
You can do board design without knowing any EE material but you would benefit from working knowledge of E&M and transmission line theory.

Look at dev board layouts and schematics since they're usually available. Cost is the main limiting factor for a hobbyist, you can design all sorts of fancy shit but it'll cost an arm and leg to produce in low quantity. Look at Oshpark design rules for pretty standard capabilities.

what are some rule of thumbs to properly simulate circuits with frequencies beyond 100 MHz?

like how do i know whether the simulation results are actually close to the reality or not

>>1160899
Your PCB is an integral part of the circuit and the parasitic inductances and capacitances of your components matter. There are simulators specifically for RF stuff.

>>1160920
do you have any experience with those simulators and might recommend one? mostly for PCB stuff

>>1160933
Not enough to be mentioned. Keysight's ADS is one of the best known such packages and it works well enough to be useful at microwave frequencies.
SPICE can be ok at lower frequencies if you carefully include parasitic stuff and design the PCB to minimize extra parasitics. It has worked well enough for my < 300MHz stuff.

>>1159145
Quality soldering lol, whats your temp at?

>>1160445
At least the other joints look like they make contact

>>1160950
I thought it those were pre-soldered out of the factory, but I may be wrong.

>>1160950
>>1161045
Yeah, that's how it came straight out of Shenzhen.

>>1160420
Look up KiCad

>>1158794
Looks good!
You may want to change how your silkscreen looks for your diode footprint from that little dot to a line. If you ever use that footprint for a production design your QC will thank you, any AOI programmer will thank you and you PnP guy will thank you.

>>1160533
>lattice
You masochist you
>I wonder if there are enough cells.
7k LE, 95 I/O
My guess would be no

>>1160899
Ansoft Designer. There's a student version still floating around somewhere.

>>1161096
>KiCad
not him but jesus christ is this hard to use

how would i add an inline volume control to a 3.5mm jack im adding directly to my amp input? just an inline potentiometer? how could i use one volume knob with both left and right channels while keeping them separate?

>>1161175
Make the pot control two transistors for each channel?

>>1161175
dual pots exists

>>1161295
Oh look you're right I've never seen those before. What value should I Get if the audio source is just my phone?

>>1161294
Would you happen to have an example circuit I could look at? Also I don't want any amplification, only volume reduction. I'm making a direct line in for my phone jack to my car amp and I just wanted to be able to put a knob somewhere I could use to control the volume instead of doing it on my phone because I'm bypassing the radio and going directly into the amplifier.

Need a breadboard of reasonable quality. At a glance, chinkboards seem to be universally shit with contacts deteriorating rapidly with use. Any exceptions from this?

>>1161319

there's this new-fangled thing called google, it knows everything.

>>1161352
Yeah I found the dual pots jackass, I meant a schematic for non amplifying transistor volume control.

Last night I got my rf transmitter and receiver to work for my arduino. Turned everything back on today and it hasn't worked since and I can't get it to work no matter what code I upload, what board I plug them into and what wires I use.
How can I make sure they even still work? I don't know what the hell to do

>>1161357
>Yeah I found the dual pots jackass, I meant a schematic for non amplifying transistor volume control.

god, you're dense. that's exactly what i gave you: a schematic for a volume control. just wire the 6 wires to the appropriate inputs and outputs as indicated.

>>1161357
>Yeah I found the dual pots jackass, I meant a schematic for non amplifying transistor volume control.

god, you're dense. that's exactly what i gave you: a schematic for a volume control. just wire the 6 wires to the appropriate inputs and outputs as indicated on the drawing.

the only bit of extra info you need is that all the grounds must connect together, so the two green wires should be joined.

>>1161392
>I'm dense
You'd best be baiting nigger

>>1161362
could be interference?

>>1161357
>I found the dual pots jackass, I meant a schematic for non amplifying transistor volume control.
>non amplifying transistor volume control.

Hey Brainiac, could you help us out by explaining why you need a transistor volume control if it's non amplifying?
Also, how do you control the transistor to make it a volume control?
I have an idea, you could use a potentiometer for that!
In fact, with the proper potentiometer you could just leave the transistor out.

>>1161362
do you have an oscilloscope

if you're using the cheap regenerative receiver you need a supply very close to 5v or whatever it specs or it'll pick up too much noise

Anyone know why I could get this to oscillate with three CMOS inverters but not one? With one it just sat at a constant 2V.

>>1161574
Socratic question: Why do you think it works with one? How about two?

Side issue: 10F caps?

>>1161562
I unfortunately don't. And it's not a noise issue. The thing literally doesn't even work now. I have the rx and tx right next to each other and either the receiver or transmitter isn't working and I'm not sure which it is. I can buy another cheap pair but still I'd like to be able to use these now.

>>1161597
it seriously might be a noise issue though. have the arduino read the rx pin out to your serial console. if you get a static value it's dead. if you get fuzz the receiver isn't changing its bias level to exclude background interference which means it's either not getting the receiver at all (probably not, they're simple and thus robust) or it's getting fed something bad somewhere. check its supply with a meter. "5v" on that arduino could well be 4.7v which won't work.

>>1161598
Alright I'll try this thanks
I was measuring the voltage though and it was a little above 5V so that should be good

Anyone thinking of going into soldering

DO NOT DO IT

I just wasted 40 bucks on new soldering station, using brand new tip and no matter what it turned black on first use while heating up and solder just rolled off and kept hitting my desk. After spending 3 hours on adjusting the heat, and kept cleaning the tip, it was still black idk how people say "use a wet sponge to clean the tip

Well, I am doing that and tip is still black.
>weller wtc100
>weller tip .031

SOLDERING IS A MEME, DON'T FALL FOR IT.

>>1161595
I assumed it would work with one because the time constant from the R*C would give enough of a delay between the signal being generated from the inverter output to it being fed back into its input. Having three stages theoretically just makes the clock take longer, so shouldn't make a difference to whether it oscillates or not. By the looks of things the single inverter falls into an equilibrium state where it is neither off nor on. By having three gates I'm guessing the signal is amplified enough to keep the first inverter either on or off, making the equilibrium stage unstable.

Though I'll admit this is my first time messing with FETs and I did learn about not-oscillators from Minecraft.

10F caps was just part of the testing phase, higher R*C is, higher the time constant and so the lower the frequency. I've obviously misinterpreted the triggering voltage of these FETs and time constant of the caps because I thought (calculated from the 74HC04 datasheet) that those values would give me a frequency of 200pHz, as alien as that sounds.

>>1161628
Just file down the tip a little and expose some fresh metal you retard. It's just a hot nail, nothing complicated about it.

>>1161628
Like anon said
>>1161638
Then get a coat of solder on it before it has a chance to oxidize

>>1161633
You're forgetting that the FETs have gate capacitance to ground, which is in series with the 10F.

In real life it's certainly possible for a single stage to oscillate, but in SPICE land everything happens at the same time and there is no time delay.

>>1161642
I mean, gate to source capacitance.

>>1161628
>SOLDERING IS A MEME, DON'T FALL FOR IT.
literally what do you propose doing instead to join components to wires

>>1161647

Its magic, soldering is a meme.

https://www.youtube.com/user/hobcoman
I find this dude named keystone science on yourtube to be pretty cool. He mades allot of cool projects most involving homemade high voltage transformers.

Cool things he shows how to make:
>High Voltage Transformer
>$5 pocket tazer.
>microwave gun
>Oscilloscope
>Solar panel
>Wireless electricty.
>Capacitors
>Tazer Gloves
Many more

>>1161638
>Just file down the tip a little and expose some fresh metal you retard

Do not do this, at least not unless you really can't get the coating off any other way. Odd that it's even there, actually...I've never had that happen, nor even heard of it.

Soldering tips are plated with a thin coating of iron, for resistance to flux and corrosion. Remove it and the tip will rapidly start corroding into nothing.

Don't use a wet sponge. It's bad for the tip and doesn't even work very well. Use a proper brass tip cleaner.

>>1161642
So changing the capacitance value does shit-all?
*tests*
Well shit you're right, except with 10µF caps I get a 1/2 second period of 2V before the oscillation begins, maybe 4s wasn't enough time to let the single gate begin oscillating?

Anyway, about spice not including time delays, that only applies to semiconductors (and valves I guess), right? The time constant method should still be useable for making something like a falling edge trigger or this sort of oscillator, I was thinking that I just needed something to amplify the voltage coming out of the single inverter to get it to oscillate properly, but I'm not sure.

I've found that with this setup "f ≈ R/(4E8)", which means I'll have to try pretty hard to get any visible frequency out of this. Maybe using 74LS inverters would be better as they wouldn't have the capacitance.
*tests*
Ok Schottky inverters don't work either.

>>1161653

This. Do what this anon says in this post.

>>1161653
Are you the anon who told me that using steel wool as a soldering-iron cleaner was a fucking terrible idea a mont or less ago? If so, you'll be deleted to know that that steel wool is now being used by my flatmates to clean their dishes. They haven't asked me about the occasional bead of metal that falls out when you scrub really hard yet, but what they don't know can't hurt them.

>>1161666
Nice satan trips.
>>1161667
Meant to say "delighted", not deleted.

>>1161653
Hmm maybe that is why the solder won't stick? I was trying to use some old solder from radioshack that has flux in it.

IDK, I will stop by microcenter tomorrow, and pic up pic related in your post, and some new solder wire.

>>1161672
Old solder really doesn't stick well unless it has a bunch of flux. Make sure you get flux-core solder, or if you want to try to use the old solder you could also buy a tub of flux. It's sticky garbage though, so it's much more of a hassle to a hobbyist.

>>1161672
The hot tip oxidixes crap from the air. Once it has that layer on it, solder won't stick. Once it's clean, tin it immediatly to prevent it from happening.

Old solder works fine. Just wipe it with a paper towel if it's appearance isn't shiny.

For good soldering, everything needs to be exceptionally clean and shiny, including the tip.

>>1161699
hmm nvm I am looking at this solder product info sheet, and do not see anything about flux, I literally thought I bought one with flux in it long time ago.

I will just hit up my local microcenter, hopefully they have replacement tip I would need if I cant fucking clean this tip.

new solder
brass tip cleaner

On solder if I wanted to solder wires on circuit board (rc car) would rosin solder be fine?

>>1161761
>solder wires on circuit board (rc car) would rosin solder be fine?
rosin core solder would be preferred.
acid core is not suitable for electronic work

I want to diy my own sort of gameboy thing, from the ground up. Are there any processors that are good for development, in the way that microcontrollers are? I.e., lots of documentation on how to program and interface with them.
Would a Z80 fit that bill? I want to design the pcb and program the processor myself.

Britfag here started using Bestelectrics.org for my chinese arduino boards

Only downside is take 2-6 weeks

Anyone know of any UK based sellers google returns nothing that isnt out of stock

I want to make a dual band wifi antenna out of a nendoroid. is there any specific wire that I need to use, or is it pretty similar to a tv antenna and I just need the right connectors?

I want to build a circuit that is going to involve tubes. As such the board is going to have high voltage DC of about 170V to provide an adequate strike voltage.

My question is, if this board is in a place where it could be touched by other people am I legally obligated to provide some kind of protection either in form of a physical barrier or a some kind of warning label or are people responsible for their own stupidity?

This isn't a product being designed for commercial sale, it's only personal and I had no plans to make a super fancy case to house it, more of a frame really so live connections would be exposed.

>>1161628
use some lead based flux solder, it's worse for you if you burn it to hot, but way easier to deal with. Also, don't file the tip of your iron, it'll just fuck up the chinky 5buck tip more.

Hi guys, not sure if I should post this here.

I was cleaning my stove (just the metal things that go under the coil) and I went to put the coils back in, but I noticed 2 of them weren't working. I reset one and waited 30 seconds or so. A spark then came out of that burner. I unplugged my oven/stove and saw that the burner socket has burnt a whole through itself. I decided to just leave that coil out, but now the stove says it is on when it is not. Am I safe to plug it back in?

tl;dr

>clean stove
>coil doesn't work
>burner socket sparks
>burner socket has hole burnt through it
>is it safe to use

pic related

>>1161665
I mean, SPICE can do timesteps but the circuit equations are solved simultaneously. There's no physical transit time modeled by default.

>>1162049
If you're not selling it, knock yourself out.

>>1162128
Update: I unplugged the wires connecting to the burner. The actual burner knob gets power, but it has nothing to push to (if the knob is turned).

>>1161976
Why not microcontroller? That's more or less what Gameboy itself used. Well ok, I guess its main chip is more a SoC than a microcontroller, but still.

>>1161976
6502 is very popular among people making their own computers.
Active friendly forum at 6502.org

any belgians/dutchies here? Which website do you guys order parts from?

>>1162219
I will look into this.
>>1162146
I can try this too, but it bothers me that I don't know how to do it with a microprocessor instead

>>1162128

replacement burner receptacles are available

I buy four-packs on eBay for $11 with free shipping

>>1162238
Farnell and rs-online if you have a business (btw nummer), or mouser otherwise

>>1162264
thanks

>>1162245
The difference between a microcontroller and a microprocessor is pretty much that in a microcontroller you have moved RAM, ROM , Timers and IO onto the same chip. Whereas in a traditional microprocessor system those components would be seperate ICs.

Another difference is that the most popular microcontrollers like ATMEL AVRs and Microchip PICs use Harvard architecture while traditional microprocessor computers use Von Neumann architecture.
In Harvard architecture program memory and data memory are seperate memory spaces, in von Neumann architecture it is shared.


The Gameboy used a version of the Z80 CPU.
The 6502 i mentioned earlier was used in the NES (and in the Commodore 64, Apple II, BBC micro,Atari 800).
Both are still produced. And both are actually also available in microcontroller versions.

I personally think the 6502 i easier to program. And it definitely has more hobbyists using it.

>>1162279
I probably should just stick with something more familiar and easy, like a Tiva. But I will go and acquire a 6502 and/or Z80 to play with as well.

Related: anyone know any good displays to be used for this sort of thing? Maybe I can find out how to use the GBA SP screen

>>1162285
Don't give up just because something is new to you.

I am working on computer project now.
The concept is something like "An 80's computer, but with modern interfaces".

I've been wanting to build my own 6502 based computer for a long time. But have sort of never had the time and it's been to expensive to get PCBs made, etc.
Now in the last 10 years or so electronics as a hobby has seemed to bounce back, and the price of getting PCBs made has gone way down.

But in one place time had run out for me. There doesn't seem to be any easily usable Video ICs anymore. Yes, yes, you can make something easily enough to output composite video. But that's not modern. I needed HDMI.

So I decided to make my own Video IC.
Now, etching ICs on the kitchen table would probably not have been terribly successful, so I looked to using an FPGA.
A couple of months ago I knew nothing of Verilog. Now I have an FPGA outputing HDMI with both a bitmapped graphics mode and a text mode.

I also decided i needed USB keyboard input.
I found the MAX3421 USB host controller IC.
I have spent easter programming a USB keyboard "driver" in 6502 assembler for it. A month ago I knew nothing about how the USB protocol actually worked. Now I do.
(To be honest, the MAX3421 i not very well documented. And the USB protocol is not very readble. I'm not sure I would have managed without looking at the sources for the Arduino host shield library which uses this IC.)

For now I have used a "soft" 6502 syntesized in the same FPGA. But I have now designed a PCB to interface the FPGA devkit to a real 65816 (16 bit version of 6502).

i want to amplify an input signal in a way so that it becomes a somewhat rectangular waveform 0V/5V

i thought a common base amplifier with a good amount of gain could be the way to go, pic related

is this generally a possible approach or nonsense? probably would have to use a different operating point though

Maybe I could have looked a little more before delving into the phone to find the type of Qualcom CPU this thing has. Oh well. Whatever excuse to crack something open, I'll take

I'm trying to figure out why my transformer secondary keeps blowing. Suggestions? I'll be doing an oscilloscope trace and hopefully it'll tell me when

>>1162521
>50 MHz
Are you REALLY going for 50 MHz? If you are, even if it works in sim it would probably be difficult to get in practice. If you can handle the transition delay, there are high-speed op-amps with a gain-bandwidth of 50+ MHz. Just have your rails at 0 and 5V and set a vref at 2.5V and have the gain be open-loop (or maybe set it to 10x or whatever to stabilize it).

Technically you could just use a not gate or comparator, but the not gate could have transition issues around 1/2 Vcc

>>1162600
Shorted cap? Bad diode?

Does anyone know if there is an NEC code on on whether a light needs to be installed within a certain distance of the work area of a control panel? Or is illumination considered to be covered by the panel gfi

Hey guys, fairly new to working with electronics and building shit and wanted to ask a question about salvaging parts. Recently I got a part time job at an office supply store and they have these recycle boxes full of electronics in the back. Nobody keeps track of what's inside and the camera doesn't have a clear look at them or you if you decided to go rooting around. So for the past few weeks I've just been digging through it trying to find good stuff. All of it is basically junktops or printers but on occasion I've found old shitty phones.
Anyway, my dumb question is whether or not I can just take these old phones (blackberries, smartphones, shit with big screens basically) and salvage the monitors? Like, could I connect one of these non-broken screens to a rasp pi and just have it work? If it doesn't "just werk", how can I make it work? This isn't really just with monitors either, I don't how to salvage parts from broken shit and I'm scared to just start soldering shit and hoping for the best.

Do anyone have any experience with this soldering station. I was thinking of buying it for my first one.

https://www.amazon.com/X-Tronic-3020-XTS-Digital-Display-Soldering/dp/B01DGZFSNE/ref=sr_1_1?s=hi&ie=UTF8&qid=1492401718&sr=1-1&keywords=X-Tronic+Model+%233020

>>1162674
If you manage to extricate the displays without damaging them or their wires, which may be difficult, you'll most likely have trouble figuring out how to interface with them with a device like your pi. Typically hard to find datasheets for things like that where the manufacturer doesn't want you to play with it

>>1162689
Would it really be that difficult? I remember seeing some videos of people making emulator machines using old portable dvd players and just being able to connect those monitors to the pi. Or is this exclusively a phone thing? Thanks for the answer by the way.

Need some help bros. Set up a solar panel and battery to run some lights but it seems like I might need another solar panel and battery as what I have isn't capable to charge the battery unless it's a really sunny day.

I need to run the lights 24/7 on battery power, they need 5w 12v so 0.41 amps. I have a 40w 12v solar panel and a 15ah battery, the setup died about half way through the day.

I didn't really account for bad weather. Where I'm at right now is thinking about getting another 40w solar panel or two and another 15ah battery. Didn't really want to spend this much on a solar setup for some lights so I was wondering what you guys thought I should do.

>>1162603
actually would like to go for a higher frequency than that, just picked 50 for starters. i didnt want to use OP amps because i figured those would have trouble at high frequencies or be expensive if not.

whenever i saw high frequency circuits they were done with a few transistors so i thought it wouldnt be too unrealistic to pick a conventional approach

>>1162685
don't know that one in particular but it actually looks pretty solid for 50 bucks

>>1158696
Hello /diy/, /ohm/

I just wanted to ask about this:
I want to control a brushless motor for high rpm.
If I get a 48v motor rated at ~12k rpm and feed it 24v, will it spin at 6k rpm?

Or if I get a 12v motor @ 2k rpm and give it 24v, will it be able to spin at 4k rpm?

Would either scenario be inadvisable (eg. kill the motor)?


Any good controller I should get over any others?

>>1162740
what is the size of the panel and how many hours of sun do you have during the day?

the panel wont just deliver it's maximum power as soon as a sunray strikes its surface

>>1162764
Certainly it is possible with discrete transistors, but that requires you to actually know what you're doing. Consider using faster transistors, too.
Also, driving an opamp into saturation isn't usually exactly the greatest idea if you want speed. Use a comparator instead, they're designed that in mind.

Pic kinda related. This has G = 40dB at low frequencies (< 50MHz) and about 14dB at 500MHz. Output (before MC1690) is ECL level. Transistors are MMT3960A.

>>1162778
okay, will look into using a schmitt trigger/comparator instead

regarding transistor speed: isn't the transistor sufficient as long as the transition frequency is way beyond the used frequency? in my case 50MHz vs. ~100MHz?

>>1162779
Yeah, but 100MHz isn't "way beyond" 50MHz. fT is the gain bandwidth product of the transistor, meaning that your 100MHz transistor will have a gain of 2 at 50MHz. Well ok, it isn't that simple in practice, but the basic idea is this.

The same idea applies to your normal voltage feedback opamps. "100MHz" GBW opamp sucks shit at 50MHz.

>>1162780
yes, i see what you are getting at. i should've known better.

thx for the input

>>1162777

it's probably 20 inch by 30 inch. i thought i would get at least 6 hours a day but today i only got 2 because of cloudy weather.

>>1162784
hows the weather in general where you live? it sounds like one panel will only be enough if you get really lucky with the weather

>>1162775
The motor speed wouldn't be predictable. In an AC motor the rotation frequency can be tied to the cycle frequency in some cases, but with DC you're fucked at predictability. In general, run the motor at a PWM cycle first, then try lower voltage. Even a glance at wikipedia shows brushless have their own control circuits, so literally you might be able to control the rotation speed by modifying a timing resistor on the board. Note you probably would go off spec.

>>1162778
Since you seem knowledgeable I want to ask, have you heard of a design to amplify 1MHz 100Vpp sinusoidal, to an output power of at least say, 200W? I've got a situation which calls for it and I have a design, I'm just looking for ideas. Doesn't need to be perfect, but the design is supposed to be variable voltage (downwards), variable frequency (up and down), and only needs to be on for a few ms at a time.

>>1162787
1000Vpp*, which is ~350 RMS/500 0-pk

>>1162787
Sounds rather special load. I'd start by checking the standard solutions used to drive whatever your thing is and consider more generic solutions only after that.
That said, transformer match to a more normal power amplifier would be a pretty common method.

>>1162787
is this some ultrasound application?

>>1158696
I want to install an led tube lamp in my kitchen.

The lamp has a screw terminal with two screws (and inputs). One is named L and the other one is named N.

In the kitchen there are also two electrical cables which I assume should go into this screw terminal. These cables were previously connected to a incandescent tube lamp that I removed.

How do I know which cable goes in which screw terminal? What does "L" and "N" mean (I am located in Germanistan btw)? The cables coming from the kitchen wall are blue and white.

Should I take into account voltage and stuff? I mean, I am just replacing incandescent lamps with LED lamps.

>>1162943
old house? is the cable really white or grey?

N=Neutralleiter
L=Phase ("da wo spannung drauf ist")

normally N is blue, but sometimes the colors might be different due to times changing. easiest way would be to measure

sooo, let's say that I have a device (dj mixer) that runs on 12V AC, how is the on and off switch wired?

The AC jack is shit and I'm thinking of wiring the power supply directly to the board, I can't do that because it's way to cramped in there though

there are 2 wires (one white, one red) that go to the on/off switch, are those both power leads or do those belong to some extra circuit that turns power on some other way?

>>1162775
Brushless DC motors are driven from a controller which will let you vary the speed. The motor's rated speed is a maximum; you can run it at any speed up to that.

Basically a "brushless DC" motor is actually a 2-phase or (more usually) 3-phase AC motor, but it's designed to be powered with low-voltage, variable-frequency "synthetic" AC from a controller, rather than from 50/60 Hz mains.

If you have a BLDC motor with a built-in controller (like the sort used in PC fans), you probably aren't going to be able to vary the speed (by more than a few %).

>>1163019
One side of the switch will be connected to one of the terminals on the power jack. The other side will be connected to the circuit.

>>1162943


Blue is your hot, or more accurately, "switch leg." White is a neutral

Light bulbs are resistors, and therefore it matters not which wire goes to which. It will work either way

Identifying (marking) the terminals it to satisfy the NEC.

>>1163019

Also, the voltage etc should be fine. Of you were curious, if you live in the US, you most likely have a 200amp 220volt panel. Your lighting circuit is probably 14awg wire on a 15amp breaker

Check the wattage on the bulb. At your panels voltage, and your breakers amperage, will you have enough power to satisfy the wattage of the bulb? Most likely yes, unless you are trying to power up like grow lights

Could someone please create a discord for /ohm/ ? If one already exist, please post a link.

i asked this over in /g/ but no response yet

I have cat5 cables running through my house as a telephone line

they all run straight to the outside which is where the phone company's box is

can I just hook an ethernet switch up in the box and have my regular wireless router still inside the house?

>>1160599
btw, wouldn't the n channel have the same problem with the 'off' period since Vsource would be vout, and the gate would be at ground? So if Vsource is 30V, and T1 switches on, the gate would be at 0V which would exceed Vgs ratings? same problem, but now its just moved elsewhere no?
not to mention with that high side driver, isn't it doublign the voltage? so i'd have way too much voltage? lol
seems like p-ch would be easier, unless i somehow find a mosfet driver chip

I'm in need of a distance sensor that I can install easily in a car bumper, the main objective is to assist me while driving, since I'm blind from one eye and depth is kind of tricky, it would be connected to an arduino that sends data to a custom android app I'm making.

>>1163087

Yes, I know, this is DIY but some things aren't worth the trouble.

Google 'automotive backup sensor'
For $15 you can get a radar system with four transducers and a display to mount in a convenient location.

>>1163129
Fuck this nigger.

>>1163087
Keep doing what you're doing you magnificent bastard

Please help, I am retarded. I am attempting to reproduce a speaker amplifier but on a much smaller breadboard, for a personal project. Circuit diagram is in link.
http://afrotechmods.com/tutorials/2017/01/17/how-to-make-a-simple-1-watt-audio-amplifier-lm386-based/

I have everything wired up, but nothing seems to happen. When I hook up a phone or mp3 player to the circuit, nothing but silence. Nothing is overheating either, though. It's evident that I either have the wrong parts or have wired something up wrong. I have never done something like this before, and though I have a light understanding of how to wire stuff up, I'm a bit lost. Can anyone point out any errors that I may have performed, or if I used the wrong parts? I followed convention when soldering the speaker wires in, with red as positive and black as negative.

Parts List:

Amplifier
-https://www.digikey.com/product-detail/en/texas-instruments/LM386N-4-NOPB/296-43960-5-ND/148192

Wire
-https://www.digikey.com/product-detail/en/adafruit-industries-llc/288/1528-1750-ND/6226987

1k Ohm Resistors (x2)
-https://www.digikey.com/product-detail/en/stackpole-electronics-inc/CF14JT1K00/CF14JT1K00CT-ND/1830350

100mF Aluminum Capacitor (x2)
-https://www.digikey.com/product-detail/en/nichicon/UVZ1H101MPD1TD/493-13464-1-ND/4342175

1000 mF Aluminum Capacitor
-https://www.digikey.com/product-detail/en/panasonic-electronic-components/ECA-1EM102B/P10380TB-ND/268465

100nF(.1mF) Aluminum Capacitor
-https://www.digikey.com/product-detail/en/nichicon/UVR2A0R1MDD/493-1136-ND/588877

-9V Battery Holder
https://www.digikey.com/product-detail/en/mpd-memory-protection-devices/BS12I/BS12I-ND/32056

Breadboard
-https://www.digikey.com/product-detail/en/seeed-technology-co-ltd/319030004/1597-1264-ND/5488148

Jack
-https://www.digikey.com/product-detail/en/tensility-international-corp/CA-2208/CP-2208-ND/701169

Speaker
-https://www.digikey.com/product-detail/en/cui-inc/GF0771/GF0771-ND/304442

Thanks for any guidance.

>>1161956

Update, I was able to salvage my new tip after ruining it, I used hakko 599b, rosin core solder flux after some time I got it almost looking brand new, and I tin it when I dont use it.

>>1163147
>and I tin it when I dont use it.

I was taught to apply a nice blob of solder to the iron just after turning it off for any extended period.
It's supposed to protect the tip and keep it 'new' longer.

>>1163144
You have multiple grounds which aren't connected.

>>1163166

I have one green wire connecting the second row from top and bottom row to make a single ground. Row 2 and Row 17 are connected together as one ground. Nothing else goes into those two rows. I have put in the top ground two 100μF capacitor, audio cable ground, 9V battery negative, and Slot 2 Negative Input and Slot 4 Ground of the LM386 via green wire. This is linked with a green wire on the right to the last row of the bottom because I ran out of room, and the bottom row has speaker negative and 100nF capacitor negative. Is this not what is supposed to be? What did I miss?

>>1163153
essentially that is what I meant when I "tin" it, I just cover the tip in solder.

>>1163174
The two halves of the board are separate. That's why you can place the op amp like that without shorting pins 1-8, 2-7, etc

>>1163129
But my implementation is supposed to aid me in both, front and back distance measuring...

Anybody know where I can buy a raspberry Pi dirt cheap and have it shipped to Canada? Im also open to comparable linux-based single board computers. I would like to string them together in a cluster to make my own miniature data center for testing. Doesn't haven to be anything fancy, so long as it can run something like Ruby or Phyton and I can SSH into it I'm good.

>>1163223
err.. amazon.ca?

>>1163233
The key word there being cheap

>>1163234
RPi is already cheap. Find some people who threw it in their drawer and never did anything with it and take it off their hands.

>>1163068
Right, there's that problem with buck regulators. It needs a fancier level shifter.

>>1163234
which they are
why don't you just say you want them free at this point.

>>1163252
so, any ideas?

>>1163275
You could add a clamp diode from source to gate and turn T1 to a current sink by adding an emitter resistor and another BJT. Restart might still be problematic, if the driver chip decides to stop switching entirely. Your bigger problem is probably 78S40's minimum duty cycle, though, limiting your minimum output voltage and load.
Other options include driving the fet via a transformer.
Or using a P-fet instead, like you originally intended.
Or using a BJT like the datasheet suggests.

Or using a mosfet driver IC.

>>1163290
i actually haven't looked into the minimum duty cycle affecting minimum output voltage and load. You seeem like you know abit about this already, what would change about the output because of the min duty cycle?

>>1163292
Nah, my mistake. There's no minimum limit, it just stops switching if needed.

>>1163207

okay I will see if this changes anything when I get back. Thank you for your help.

I've got some old computer PSUs and I'm thinking of making a "breakout" for it (instead of converting the PSU itself and consequently having it crap out on me) so I can turn it into a fancy bench power supply. Complete with adjustable/programmable voltage and current limits. Nice LCD and everything.
What's a good (simple/cheap) option for current limiting? Since ATX power supplies are capable of outputting quite a lot of amps I'm thinking I might want to not artificially limit it to max 1 amp or something. Although for electronics projects I'd probably rarely use anything above 1-2 amps so maybe it's not such an issue to have a relatively low maximum current.
I already saw the Dangerous Prototypes breakout which is nice, but I want to make something fancier.
Any advice for taking on this project?

>>1163566

dont do it. output voltage too small, case too big and heavy. dangerous currents that can melt you components if you screw up.

get a mini-stereo from the thrift store for under $10, and take out the transformer. should give you something like 50Vct which will give you a +-30V tracking supply using any of hundreds of designs on the interbutts, with or without current limiting.

Is there any special way to twist 3 wires together and make them stay together as a twisted set without breaking them, sort of like how rope will just coil into itself and hold it's shape?

>>1163207
>>1163166

This was actually the problem. The sound is kind of choppy, but it works now, and that's plenty good for me. Thank you so much for your help.

>>1163566
Assuming that you're using a buck regulator, you limit current the same way as voltage: stop generating pulses if the value exceeds the threshold.

I've learned some things designing and testing a diy power supply.

highly recommended.

it will probably (definitely?) cost more to make a decent one of your own than it would to buy a good solid one that is professionally made

>>1163606

for best results you can use braid over a set of wires, or lace them using waxy cord, like dental floss.

not as effective, but if you just spin them around hard, using a drill for example, they will tend to keep that twist for a long time.

>>1163252
What about the problem with boost regulators having to pusl massive amounts of low voltage high current in order to get higher voltage medium current?

>>1158794
Add fiducials

Hi, I want to make my old car have automatic crash avoidance by using a quick returning laser rangefinder and my arduino by hacking the brake pedal to accept both stepping and the controller. It would also work better if I could get live information from the obd2 port. What do I need to do this besides the arduino itself and what software exists for rangefinding with vehicles?

>>1163818
What about it?

You can't beat conservation of energy, so mean input power >= mean output power, so the mean input current has to scale up in the same ratio as the output voltage scales up (plus extra for inefficiencies).

On top of that, for a boost converter in discontinuous-conduction mode (DCM), the peak input current is at least twice the mean input current, so RMS input current is much higher than RMS output current.

OTOH, continuous-conduction mode (CCM) boost converters are hard. Because you have (1/2)*L*I^2 energy stored in the inductor, and if you stop pulsing it gets dumped into the output capacitor. Which means that you can't just use simple hysteretic ("thermostat") control based upon the output voltage. In practice, you end up with a constant-current regulator with the current determined from the output voltage using a PID controller.

And even then, preventing overvoltage in the event that the current draw drops suddenly requires either a large output capacitor (so that (1/2)*C*V^2 is much larger than (1/2)*L*I^2) or an active sink (e.g. a power MOSFET across the output), or a combination of the two.

Does anyone know of good, relatively open SoCs that are powerful but still easy to deal with?

>>1164309
>powerful
>easy

pick one.

I'm playing around with some boost converters and I can't figure out why my converter isn't quite working right. In simulation and on breadboard I am seeing a DC offset on the Vds waveform which should not be there which explains why my current draw is really high. With my power supply current limited to about 200mA it maxes out at 200mA and starts dropping voltage. I expect the current to spike when the MOSFET is on since it's basically a dead short but it shouldn't be conducting all the time which would result in a lower average current. But that DC offset (blue waveform) means the MOSFET is always conducting and idk why.

Additionally when I vary the frequency or duty cycle on my function generator the output voltage does not change. Why?

>>1164357
Oh by the way the MOSFET is not actually a IRF9130. It's an RCA 7264P-3B. There is no spice model in Multisim for it nor can I find a datasheet but it is a P-channel MOSFET according to a transistor tester. It probably doesn't make much of a difference but it's worth mentioning.

>>1164357

where's your load, nigger?

>>1164359
It doesn't work with no load? I figured it would have some open circuit voltage which would decrease when a load was applied.

my laptop is having an issue where it will not charge the battery but will draw power from it (when not on ac). currently the pack is almost drained so i want to bring it back up to make sure it doesnt lose lifespan from being discharged for however long it takes to deal with this. how do i charge the pack with a power supply? it is an 8 lithium cell pack that gives 14.8v and 5200mah so im assuming its 2 parallel sets of 4 cells in series rated at 2500-2600mah each. it has whatever protections built in that you would assume any laptop battery pack would. what is the voltage and current limiting i should set my power supply at and how will i know that the battery is done charging?

>>1164359
ya mum walked away with it >:D

>>1164041
>what about it
passing 20A at 5V in order to generate 30V ~3A might be problematic for the 5V circuits

>>1164384
And why is this is relevant here? No-one, except you, is suggesting a step-up regulator.

>>1164388
Because he mentioned that buck regulator had the problem of keeping a safe voltage on the mosfet gate, while a boost doesn't have that problem since it switches to ground

How do i go about packaging data when sending over serial with Arduino? Ultimately i want to pass ardupilot telemetry data and RC-control signals via single radio link.

I have single serial radio link that should act as bridge for serial data and also passthru pwm data.

My idea is that i some how package the serial data and pwm data and sent it as serial data over the radio link. How does one package data? Do you know if there is a library already available?

The radio acts just as a transparent serial link.

Radio: E32-TTL-1W 30dBm SX1278 LoRa 7.5km Long Range 433MHz RF Transceiver Module

>>1164439
Found a premade solution
https://github.com/GraemeWilson/Arduino-Python-Framing-CRC16

I will just add a byte telling if coming stream is telemetry or RC control.

>>1164376
>14.8v and 5200mah
> so
>2 parallel sets of 4 cells in series rated at 2500-2600mah each
> then
>what is the voltage and current limiting i should set my power supply at

if 18650 batteries - 4 x 4.2v = 16.8 volt limit
5200mAh - 0.5A current limit

> and
>how will i know that the battery is done charging?

when the current limited voltage reaches 16.8 volts
just to be safe, you should probably stop at 16.7

I got a shitload of Darlington 1n914 transistors. Now, I have to wonder... Which prongs are CBE? I have a lightbulb PCB that I think uses the same transistors, that says it's ECB with the rounded side pointing away from you, but that feels strange. Any way I can get some concrete proof as to which goes where?

>>1164700
*2n3904, my bad.

>>1164041
You know, you could use a zener to regulate max voltage. Kinda the point of em.

>>1164408
But a step-up converter isn't really a practical option here. Step-down is, even if driving the mosfet is bit more tedious.

>>1164700
Just check the datasheet. It has a picture showing the pinout.

>>1164719
>But a step-up converter isn't really a practical option here. Step-down is, even if driving the mosfet is bit more tedious.
I know. I was mostly commenting on how pushing massive amounts of current means possible heat problems and voltage drops all over the place and that it isn't outweighed by the prospect of just figuring out how to drive a buck converter better
Sadly, step up does seem to be more efficient than buck, though only slightly and not that important in my (our?) hobbyist level applications.

btw do you know how to figure out rise and fall times for mosfets as it pertains to drive current? I'm having a hard time finding a solid gate driver at digikey in DIP format that will do highside n-ch or p-ch (though obviously n-ch is way more common as is lowside driving)?

the SMD packages are way more common obviously, but fuck smd soldering or designing part of the board for smd

Also for anybody else, do you guys know of a pcb making service that is solid and doesn't charge kidneys for making them? i've settled on expresspcb but dunno of any others.

>>1164704
2N3904 isn't a Darlington pair. It's an ordinary NPN transistor.

>>1158696
For the love of god, what is the name of this type of microswitch and where do I buy more?

It's designed to send a high signal when a post on a rotating gear trips the switch. I need one that operates in both directions. I've used them before so I know they exist, but I can't figure out where to get more.

>>1164779
high signal? tripping a switch?
wat

>>1164776
not to mention 1N914 isnt even a darlington array, its just a diode

>>1164727
Mosfet driving is 100% based on how quickly you accumulate charge i.e. the output resistance of your driver->current->charge.

I've been coming into it because I need to switch mosfets around 1MHz, and while N-channels have less charge than P-channel, they're both around 50nC for what I'm doing. 50nC/50nS (estimating a rise/fall time) means I need at least 1A of current available, preferably higher. It's going to be shit.

>>1164799
damn. well i did see that digikey has quite a few 1+ amp driver chips

for my SMPS application, with my LM78S40, its pretty low at 20kHz - 100kHz so i kinda wanted to know so that i can find a DIP package that had the necessary current requirements.

>>1164803
100khz isn't much, here's how you can calculate it:

find the period of your cycle 1/f = 10us

You have rise + fall so divide by 2 = 5us.

Give a guess on your "worst" performance you'd like, say 5%, so .25us. If you have 50 nC of charge, you need only .2A. If you'd tolerate 10% you could do .1A.

Of course the faster your voltage the more amps you can push in for a certain resistance, so switching nearer to the gate-source breakdown voltage (not that close, but like 3/4) would go faster than 1/4th. If you're using it as a switch you want to drive the gate as high as possible anyway.

>>1164811
Ah okay i see what you're doing. dq/dt. I should've thought of that derp.
Guess I don't need something in the 1+ amp range. Though that'd certainly help with switching losses
Thanks again anon

I got myself a 80x64p thermophyle array module. The problem is the ethernet connection is kinda unstable (the usb port is for power only). would it be possible to get data from the sensor itself while it's still connected to its original circuit just by listening to whats going on on the SPI pins?

>>1164779

i got half a dozen of those switches from broken CD-ROMS. they're used to detect when the tray has reached the two maximum positions: fully in and fully out.

>>1164933
sure if you know the frame timing and data format

it would be easier if you had the datasheet with the commands and responses list

How do I fix this?

Anyone with experience with op-amps in multsim?

The circuit establishes VREF=1.65V at the inverting input, and by using 0 and 3.3 as the non-inverting input, it successfully goes between -rail and +rail, respectively (the gain is rather arbitrary, I'm just adding it for stability).

My problem is then I want to leave the input floating, and have the output 0V, or as close as possible (+/-1 would probably work, so I could lower the gain resistors to 20x or so). I added a 100kohm resistor between the inputs (which should tie them to the same voltage, albeit with a high cross-resistance)

The issue is multisim has a convergence error, and doesn't know how to resolve it. My max timestep is 2e-10, so it's not like it should be a rate error. If I don't have the 100k everything is fine, if I add it the circuit fails to converge.

>>1165115
Fucking hell: if I add a measurement probe during the successful simulation it fails to convergence. A fucking measurement probe causes it to fail to convergence, how is that possible?

>>1165115
>>1165122
Alright, I think I got most everything resolved (don't know why the things were shitting themselves, one thing was I had the R1/R2 backwards) but now I can't set the integration back to trapezoidal, only to gears. Instant failure with trapezoidal.

>>1165129
nvm, this circuit is just failing fucking everything. Convergences once, then I add a probe and it fails to converge. Sage goes in every field

>>1165115
Never used Multisim, but typical solutions to convergence errors include adding small resistors, capacitors and sometimes inductors near places where you see abnormal currents or voltages. Very high value resistors can help too.
In this particular case you can also try different opamp and regulator models.

Trying to control some servos with two arduinos using rf. I have it transmitting the correct data but I can't actually get a servo motor to move. I tried connecting the servo to either arduino board and it stops transmitting or receiving, and I tried hooking it up to its own supply with 4 AAs but nothing happens then.
Any idea what could be wrong? The servos do work, tested with other code.

>>1165143
post rough schematic

>>1165115
I redid everything with a "proper" differential input circuit and it now works, but now I just have to figure out if I can decrease the rise/fall times.

>>1165159
Use a comparator instead of an opamp. Use positive feedback instead of negative. Add a Schmitt trigger to the opamp output if desperate.

>>1165164
If you can find me one that does at least, +/-5V, and compares 1.65V to 0 and 3.3V, and works up to 1.5Mhz, I'm all ears.

I need to drive mosfets, so preferably the highest output current and voltage you can get (+/- 15V would be best)

anyone know of any good looking nonmetallic usb stick enclosures? the ones google is showing me are too fat or ugly. preferably black and thin but whatever.

>>1164862
>>1164811
Got any ideas for current sense?
dedicated current sense ICs tend to be SMD packages and also use very very small value resistors.

I don't know how accurate a regular op amp would do in difference amplifier topology, esp with all the extra resistors needed, not to mention I don't know if the feedback/gain loop would exceed voltage maximums

And then its also complicated by wanting to be able to do sensing at the terminals

>>1165316
If you have an oscilloscope, you can just watch on/off times, or from calculations, max amperage -> max charge distribution.

>>1165316
The main issue with current-sense amps is that one side of the resistor is often one of the amp's power rails, and the other side isn't very far off. Whereas general-purpose op-amps tend not to like having their inputs driven close to the rails (at the very least, they tend to be quite non-linear).

>>1165338
this can be solved with a charge pump that'll only consume one microcontroller pin. the real issue is that you can't build a good discrete instrumentation amp even with trimming unless you're using precision resistors and reasonably low offset amps. at that point you're ordering parts so you'd might as well just get a packaged instrumentation amp like the ina126.

>>1165326
>charge distribution
wat
I'm talking about ~30V on the inpt of one of the amps

>>1165338
>The main issue with current-sense amps is that one side of the resistor is often one of the amp's power rails, and the other side isn't very far off.
Wait, what's the issue there?

>Whereas general-purpose op-amps tend not to like having their inputs driven close to the rails (at the very least, they tend to be quite non-linear).
Yeah I also can't figure out how to measure the linearity. But even still.
I want (need?) to measure 0 - 10A. or downspec to 0 - 5A
LT6100 seems to be able to do it but like i said, SMD packaging (fuck), need a small value sense resistor (fuck, and potentially expensive too)
in fact i haven't found any dedicated current sense ICs that fit the bill that come in through hole (DIP) packages

>>1165343
now that i've read your posts i realize you need the current sensing for a power supply. is it for user feedback or as part of the control loop? if it's part of the control loop then scale, offset, and linearity (to an extent) don't matter much and you can comfortably use a discrete amplifier. in fact it'll be potentially more annoying to use an op amp because you'll need a few mhz gbp (>100khz*5-10 harmonics*5-10x gain).

>>1165349
>user feedback or as part of the control loop?
both. I intend for there to be a current set (current or current limit?); current sensing, so that I can compare the desired current isn't exceeded, or kept at constant current; and for there to be a readout of both the current set and the current out. I can easily scale for outputting too. its mostly the sensing part that I'm having a problem with at the moment.

Some of those precision and/or high wattage resistors, especially the ones that are on a chip-like package, and have 4 terminals are tits expensive

I also have not read up how gain bandwidth affects shit. but on the topic of op amp / gain related issues, i'm already not completely certain how to deal with op amp oscillations in the feedback loop either

>>1165358
and by "deal with" i mean going beyond simply throwing resistors and capacitors in places and hoping it works. I've seen / heard shit about phase margin and bode plots but that feels like it's beyond my means

>>1165359
It's kinda fundamental to what you're trying to do so you might as well learn it breh

>>1165388
>learn
yes

>able to put it into practice
i dunno if i have the means

but as for learning, do you have a general explanation to help whet my appetite? pls halp

>>1165096

if the only problem is the short-circuits caused by the solder, then there's a super simple solution: drop some rosin flux on the contacts and sweep your iron across them. flux is like magic, it makes all the solder jump to the pads, and none in between pads.
comes in bottles and in pens.

>>1165253
For example LM319. It needs a mosfet driver (or at least two transistors) to buffer the output, but so does pretty much everything else, if you want to drive mosfets at 1.5MHz.

This is supposed to be a schematic for an analog optoisolator built around a LED and two detection photodiodes optocoupled in a HCNR200/HCNR201 die. I have some problem grasping how it is supposed to work, especially the amplification bit. Can someone help me to understand the theory of operation of this circuit?

>>1165442
The basic idea is the same as in pic related.
The transistors just form an amplifier with lots of inverting gain. It is made of two emitter followers, both having plenty of current gain but no voltage gain. The PNP-NPN pairing kills the offset voltage. So, the voltage at Q1's base is reflected across R4, which is turn sets the LED current.

>>1165413
I was using fake chinese RMA-223, that might've been the problem.

>>1165413
>comes in bottles and in pens.

Just as a PSA, the pens are ass. At least, the weird, felt-tipped ones that you press on to release the flux.

Ended up getting so frustrated with my last one that I drilled a hole in it, drained out the flux, and now keep it in a couple syringes instead. Much more usable.

>>1164811
>>1164803
I've ran into another set of impasses that i've forgotten about previously.
the Rsc in the datasheet...
I'm operating from a 2x 15V, 100VA toroidal transformer. Buck topology.
So would that mean that I would only need to choose a value for Rsc to account for ~100VA / 30 = ~3.3A? or would I have to select Rsc for the intended output of 10A max, or 5A max if i despec my intended design?

As for the inductor, does it also experience just the ~3.3A from the transformer secondary? or would it experience the max 10A (or 5A) current?

Yes I know there are equations there, yes I used them, no i'm not blindly following them (hence the questions)

I also notice that if i want a lower max current (say 10mA) i require a massive inductor? so does this mean I wont' be able to run buck with lesser currents? What the fuck

Looking to make myself a little pick and place, but with a 1W laser for soldering.
I'm looking for more or less pic related but with a driver. Not sure if this thing's supposed to be driven from the mainboard of a CNC or just powered by it.

>>1165480
>soldering with laser
are you sure that's a good idea, son

>>1165490
Hot air rework can just blow stuff to the side.
After thinking it through though hot air's probably better than a laser.

Dumb question: How do I calculate the amp loss from a step-up converter?

I want to power 2 or 3 pcs of 120mm fans from a USB charger.

FAN spec:
12V; 0,09A; 1,1W

The USB chargers are 5V. I have 0.5A, 1A and 2A chargers.
First I need a step-up converter 5V->12V. eBay has many.
Then I also know there is a 15-20% inefficiency.

But how do I calculate the new amp I will get?
Basically, I want to split the converted 12V wire that comes from the converted into two and lead those into the fans. (or three, but two would be more than enough I think.)

My hunch is that, for example with a 0.5A charger:
> 12/5 = 2.4 (12V is 2.4x 5V)
> 0.5/2.4 = 0.2083 (calc new amp)
> 0.2083*0.8 = 0.1666 (due to 80% inefficiency)
> 0.1666/2 = 0.0833 (split in half)

Is that correct?
0.083 is below the official amp spec which is not bad (it will spin a bit slower), I suppose I can only get lower but not higher than the specs.

> Said fan:
> Silent Eagle 1000 120 mm
https://www.sharkoon.com/product/1682/SiEagle#specs

> Converter (just an example):
http://www.ebay.com/itm/USB-2-1x5-5mm-Male-Connector-Plus-DC-5V-to-DC-9V-12V-Step-up-Module-Converter-/222404557510?var=&hash=item33c8583ac6:m:mLPSvoxrD9qCweAvIWueYbQ

Charger specs are USB, so all are 5V and 0.5A, 1A, 2A.

>>1165498
>Is that correct?
Yes, even if your method is bit roundabout.
>0.083 is below the official amp spec which is not bad
You'll be overloading your USB charger and the results depend on how its overload protection is designed.

>>1165512
>Yes, even if your method is bit roundabout.
Well, pls teach me fampai.
> You'll be overloading your USB charger and the results depend on how its overload protection is designed.
So I should have a fan that requires MORE amps?

If I calculate with 10% ineff, I get 0.093A/split cable from the step up converter. And each fan needs 0.09A.

Or I can use a 1A charger that would give me 0.1875A for each fan.
But overpowering the fan would damage them, wouldn't it?

Noctua has max power input specs:
http://noctua.at/en/nf-a14-pwm/specification

To me it looks like the 0.9A split+step-up power (5V/0.5A charger) is the sweet spot.

I was given what /o/ called a super simple circuit to draw, but I havent covered some of the material (ive only gotten to the very basics) and was wondering if anyone had any advice on how to do this, or where to go to learn how to do something similar to this diagram.
A circuit using 3 relays and two fans, it will be controlled by the computer. They need to be wired in series for low speed and parallel for high speed (label all relays) and show the coil and armature. The fan motors have 8ohms of resistance. (I have to write the voltage drop on both circuits and amps, and label the wire and size on the circuit).
I typed it all because i dont know if some places wont have all of the parts for me to put in.
Thank you very much

>>1165518
Available input power: 5V * 0.5A = 2.5W
Maximum output power: 2.5W * 0.8 = 2W
Maximum output current: 2W/12V = 0.17A
Well ok, same amount of math. The efficiency rating is related to power, though, and only indirectly to current.

>So I should have a fan that requires MORE amps?
Huh? Your fans want 1.2W each and the resulting 2.4W exceeds the 2W maximum output above. Your step-up switcher tries to output the required 2.4W, drawing 3W from input and your 2.5W charger might not like it.
Maybe I misunderstood something?

Have anyone bought a PIC development board that you could recommend?
I like this one by mikroe but it only supports their mirkoC IDE and not MPLAB.

>>1165524
Here is where I got the idea from by the way: https://www.youtube.com/watch?v=INfSuqxtvIg
He is using standard 0.5A (or more) output to drive the fans through the step--up converter.

I could also use 4 1000RPM 80mm fans.
Each eats 0.1A (don't ask me why it requires more power than the 120mm one).
So 4x0.1A = 0.4A.

Using a 5V/1A charger and 90% ineff, I would have 12V/0.375A.
That is below 0.1A for each fan.
Would this be better? (Not sure if the ~10% missing amp would damage the fan in the long run.)

By the way people usually use a simple USB cable, cut off the ends and tie it on the 12V fan without any conversion lol.

>>1165472
I'm now thinking maybe a pwm controller (almost the same thing) is better.
so many varities of chips to choose from each with their own weird shit

Please help me make a 4 bit ALU

>>1165579
What functions do you want? Addition and subtraction are easy enough.
Multiply is harder.
Things like invert, swap nibbles(not on a 4 bit though 1) are tedious.
You should probably know how to build an adder, then with carry, then just chain them. Subtraction is addition with twos compliment. Any other functionality you can create via truth tables, karnaugh maps to produce Boolean expressions that you can implement with gates.
Show us what you want and what you have done if you want help with anything specific.

>>1165442
The basic idea is this: opto-couplers are highly non-linear and you can't change that.

So what you do is to have a matched pair of opto-couplers (they can share the same LED). One of them is used in an op-amp negative-feedback loop. The use of negative feedback means that the output voltage will be whatever it needs to be for the inverting and non-inverting inputs to be equal.

So the current through the photo-diode in the feedback loop will be proportional to the input voltage. And because the two opto-couplers are matched, the current through the other photo-diode will be (roughly) the same, i.e. also proportional to the input voltage.

If you search for "linear opto-coupler", you'll typically find "matched Y" opto-couplers with one LED and two matched photo-diodes, with the light from the LED split equally between the two. It's not that the photo-diodes themselves are particularly linear, but that you can use negative feedback in this way to linearise the overall response.

>>1165579
An ALU is just several discrete functions (add, subtract, and, or, xor, shift) with their results multiplexed.

If you don't need to worry about gate count, the easiest solution is a lookup table (i.e. PROM/EPROM).

Inputs: 2x 4-bit values, carry, function selector. Outputs: 1x 4-bit value, carry, overflow, zero flags (the negative flag is just the top bit of the top nybble).

How do I get better at soldering perfboards?

I tried to solder this one with just a helping hand, and it turned into an absolute mess.

>>1165646

step 1 - get perfboard without any copper.
step 2 - make sure to use very fine wire; 24-gauge telephone wire is ok, 30-gauge wire-wrapping wire is better
step 3 - get tiny ass tools to strip, bend the wire (long-nose pliers), and cut (knipex-type side cutters)
step 4 - avoid the temptation to make solder connections by bridging adjacent pins with a blob of solder, or of using component leads as wires.

>>1165588
that's real neato

How would i draw a circuit with three relays and two fans (one wired series for slow, and the other wired parallel for fast) being controlled by the computer.
I think i have most of it wired right i have it going from battery to a normally open switch, which goes to relay one (86) and 87 on that same relay goes to r86 on the second relay.
Relay 2 has 87 go to the third's relay 86 but is spliced with one end going to ground and the other going through a NO switch.
On relay 3 you have 87 and 87a one for low speed fan, and the other for high speed.
The 30's on the relays link up going to the negative end of the battery...
If anyone can help with either a site or video explaining how to do this, or could explain it themselves, that'd be amazing.
Thank you (i can post an image of my current drawing from my phone if that helps)

>>1165656
>perfboard without any copper

How do I get the wires to stick to the pad then?

Solder on both sides to secure into place?

>>1165646
Your flux is not working properly. What kind of tin are you using? What temperature on soldering iron - and what kind of iron?

Choose a tip that lets you work comfortably. Practice, practice, practice. Stay clear of lead-free tin. And did I say practice?

>>1165677
This is what I've drawn so far but I have little faith in it

>>1165689
I used a Kester lead-free solder at 425 F.

I didn't apply additional flux as the solder I used has rosin core.

>>1165697

>lead-free solder

There is your main problem, right there. Get yourself a nice roll of 60/40 tin and you can tune that horrendously high soldering temperature way down. This will also limit the flux from making a mess.

Lead in a solder is nothing to be afraid of. Just be careful that you are not going to eat it. It will not penetrate through your skin. It will make soldering easy, because it will wet the metal really well. Practice!

>>1165703
>>1165656
Any recommendation for a specific perfboard?

I'm using some random shit off of AliExpress and metal pads around perforation sometikes fall off while I'm trying to solder shit on them.

>>1165523
>A circuit using 3 relays and two fans,
>>1165677
>a circuit with three relays and two fans

It's Your homework - you need to "Do It Yourself"

>>1165783
Was asking for tips/places to read up on it. I currently don't have access to my notes

>>1165684
>>perfboard without any copper
>How do I get the wires to stick to the pad then?

you dont. you stick in the component, bend the leads a bit so it doesnt fall out. then make a little loop of wire around one lead, solder, repeat for the other leads.
it makes a much neater board, with way less chance of short circuits.

>Any recommendation for a specific perfboard?

i just go the same store i've been going to for 20 years, and choose the least expensive one. if you're an online kinda shopper, i suppose you look for Copperless Perfboard, as seen in pic.

>>1165859

this is not a particularly neat example coz the wires are too thick, and the routing is sloppy, but that's what it looks like without copper pads.

>>1165859
>>1165865
Thank you for a detailed answer, anon.

>>1165865
This style of perfboard looks fucking janky as fuck don't listen to him

Has anyone tried using an inductor which is attached through a transformer?

My problem is I need a pretty large inductance (11u-100u) that can withstand uh, 2.5kV and 12.7A peak (don't ask too many questions).

Let's pretend A) I find a core that doesn't saturate and B) I have magic wiring with perfect insulation. Could I wind mutual inductors or a transformer such that I could have a smaller inductance be amplified? I know in power classes we learned about "effectively", or in terms of per-unit, you can convert resistances and such via turn ratios, but we didn't do it with inductors.

>>1165714

>metal pads around perforation sometikes fall off

A clear indication that your soldering temperature is excessively high. Lead-free is the root reason for this.

>>1165956
>2500V
>12.7A peak
>31,750 W peak
>thirty one thousand seven hundred fifty watts peak
what the fuck
if you're making tesla coils, people tend to make their own inductors

>>1165547
>Not sure if the ~10% missing amp would damage the fan in the long run.
It's not a problem for your fan, but like I said, you'll be overloading your USB power supply. The current rating of the power supply must be higher than the load's.
Or should be. What happens when you try to draw more than the nominal maximum current depends on the power supply. Some are seemingly fine, some shut their output off completely, some reduce the output voltage and some just burn.

>By the way people usually use a simple USB cable,
If 5V is enough for the fan to turn, it's not a problem in itself.

>>1165991
Well, the amperage and the voltage are probably almost entirely out of phase.

I underestimated how significant the effect of area was on inductance, so I'm just going to have an inductor with a 2-3" diameter and like 100 turns, and then have a movable tap.

As for the transformer, I have two microwave transformers that were unsuitable (too low current), so I could always rewind those, but since I need the gosh dang current, I'm just going to go with a large single-layer winding. Hopefully I can shield it, otherwise it's going to generate preposterous amounts of radio waves.

>>1165995
it sounds like its not 12.7 amps AT 2.5kV
so you have already described the issue improperly.

Powersupplyfaggotry person again

EEfag(s) pls halp

So about that tracking preregulator (switching)
I think this circuit will work, but I don't know for certain if it might not work(nor cases where it might not).

The right side resistor network is buffered by an op amp. Then its output goes to the inverting input of the difference amplifier. Rg and Rf provides gain so that the left op amp gives the difference in voltage between those two points (without having to be exposed to 30V+, since the op amps will be powered by 12 or 15V)

The circuit should give a difference of 3.5 to 5V (depending on what i want the difference to be) all the way from zero volts output to max 30V output. (so the voltage at the top of the left side resistor network should go between 3.5V - 33.5V) Is this indeed the case?
What issues might i run into with oscillation?

The idea is for that 3.5V to be fed into the inverting input of another (third) op amp with 3.5V - 5V on the non-inverting input. The output of this third op amp would be fed to the feedback pin of the buck regulator such that it keeps a constant 3.5V - 5V DC overhead

Would this indeed work? esp. down near zero volts? With all the op amps, what instances would i experience oscillation if any? What issues would there be with first turning applying power? Also, is using this many op amps a bit excessive?

>>1166000
AND you fuck. Reread my post. You have improperly understood my post. I even said it can WITHSTAND that, not that'd it'd be running that continuously.

>>1166010
1) Learn to draw better and take clearer screenshots. It looks like your first wires shouldn't cross, but I can't tell, and your transistor has no arrows on it. You can probably find schematic drawers or something if you don't want to get a simulator.

2) if that's an NPN transistor facing right, there's no power source for the collector, and it's it's facing left, it's not doing shit. If it's PNP, it still wouldn't be doing anything productive. And that's whether or not the op-amp is referenced at that first possible node.

What the hell are you basing this on, it looks like it's supposed to be some sort of regulated output device like a battery charger, but its a mess

>>1166010
>L2draw
sorry i thought this was diy not ic

2) it definitely works since its its sitting on bread board, sans those drawn op amps. Sorry to hear about your faggot condition though.

>>1165956
>don't ask too many questions
don't expect too many answers

Hey I have a super beginner question, am new to this thing and I could really use a power supply; is building one out of an old PC PSU really a good idea? I see that everywhere when I google for ideas but my concern is those things can push like 30A.

If I were to use it and accidentally touch it would I die? I guess with ohms law I woudn't since human skin resistance is apparently pretty high but then why do they say they are 30 A? Is that the maximum they can produce? So if I connect a component it will only draw as much as it needs and I wouldn't need to worry about the high amp stuff?

Thanks

>>1166666
you have to get creative to kill yourself directly with a 12v supply. you just need to be careful with fires and inductive voltage spikes. i don't know the regulations but cheapo psus won't have quality current limiting.

30A is the maximum they're rated to supply. computer power supplies (most psus in general) provide a constant voltage under all conditions and the current changes to match the load's resistance/impedance. so if you put the positive and negative across your finger only a few microamps will flow.

babby's first pcb just arrived

i've never soldered with hot air before so this is guaranteed to fail miserably but it was fun to design and it'll be a learning experience

>>1166719
only one bridge first try. one thing i can't tell is if the thermal pad soldered or bridged but the solder mask is there so i'm optimistic.

i think i can probably get one of the three boards functional, maybe

I just reverse engineered the analog front end for a K-band radar gun and while I have a vague idea of what's going on this circuit is pretty confusing and I'd appreciate if any RF guys or HAMs or anyone with experience with microwave circuits could explain what some blocks of this circuit are doing. You don't have to go into a ton of detail unless you want to.

The part the schematic reflects is circled in red. The other half of the board is voltage regulation, primarily for varying power to the gunn diode which is connected across the two spade lugs in the back.

The entire gunnplexer/antenna connects via the RCA jack through a Schottky mixer diode. I believe the anode would be connected to the center pin and the cathode is grounded at the other end to the waveguide but it's hard to tell because the diode is buried in the waveguide and I can't really get probes in there to test it without grounding them on the waveguide by accident.

>>1166719
Where did you have it made?

>>1166811
oshpark. $3.50 for 3, ENIG included. i paid a bit more for priority.

>>1166820
>oshpark
Cool, thanks anon I'll try to remember it.
What design software do you use?

>>1166752
>>1166835
Also I can't really see the soldering. Do you have a better camera?
There are also some good videos on youtube on how to do SMD. My board is probably going to be mostly through hole with a few SMD components, so I'll probably hav to suffer the same shit too

>>1166835
altium. there's a lot of obnoxious overhead at first but bear with it and you'll come to appreciate it.

>>1166841
Cool thanks
People say that about KiCad too though, so fuk

>>1166836
and no, sorry. the qfn pictured is much smaller than you'd assume by looking at the pictures. i took that through a magnifying glass at max zoom. i think i'm going to order one of the $100 usb microscopes dave jones featured before proceeding.

I want to solder some new microswitches into an old mouse I have. I hear that mice PCBs are typically of garbage quality, and that it's very easy to lift the metal contact on the PCB when attempting to manipulate the solder.

In order to minimise the chance of that happening, should I target a high temperature (like 350C) and try to get the operation done very quickly, or target a low temperature (~200C?) and try to do it slowly?

>>1166874
If you have a good quality mouse you've got nothing to worry about. My recommendation is to add some of your solder to the existing one, just a light touch with a soldering iron to add some of your solder, do this to all pins, I do this because nowadays most PCBs are lead free and components are hard to desolder, hence for critical things I usually apply some solder first before trying to remove it all.
Then I heat the pin a couple of seconds and I remove all the solder with a desoldering pump. If you haven't applied your solder beforehand and the PCB is lead free you're going to have a bad time sucking all the solder at once.
Regarding the temperature, I don't have a set choice, too low will take longer to melt the solder and too high and you risk charring the pad if you're not quick enough, a medium temperature just works.

Here's an instructable I wrote about the topic.

http://www.instructables.com/id/Fix-a-faulty-mouse-button-in-5-minutes/

>>1161628
>being this incompetent

bump limit reached

for best response time, post in new thread >>1166999