/diy/ - Do It Yourself

[Bojangles No.393912]

greetings /diy/

i'm in need of an electronics guru. i am a noob and am still learning the basic concepts.

pic related. it's the car i'm working on. it works fine, for a few seconds, but then it stalls as if it's struggling to pull enough energy from the batter (9.6v NiMH).

any thoughts?

(this post was much longer, but the board thought it was spam for some reason)

[Bojangles No.393915]

it's an arduino uno with a motor driver shield attached that handles the large amounts of current instead of frying the arduino.

when the wheels are not touching the ground and can spin freely, i measure ~1A of current being pulled from the battery.
when i hold the wheels still and tell the car to go anywhere, i measure ~4A.

the motor driver shield is only rated to handle 2A safely.

[Bojangles No.394348]

i really have no idea as to what other information should be included with this.

#shameless-self-bump-before-sleeping

[Anonymous No.394351]

>>394348
What motors are you using? How many motors? What's the voltage under load?

[Anonymous No.394352]

Does the supply voltage drop when this happens?


It may have some kind of current limiting built into the interface board.

diy is a slow board so bump after a day or so.

[Anonymous No.394353]

It sounds like the voltage is dropping out due to motors drawing current.
Do you have an oscilloscope? Do you have the source code? You could write code that blinks an LED if it resets, which could help with diagnosing transient power problems.

[Anonymous No.394375]

>>393912

the trick to debugging systems is DIVIDE AND CONQUER!

Run the Arduino on a separate poewr supply from the motor, or run the whole thing on a gross-overkill power supply.

in general, unless you are careful with design, it's bad practice to run the logic from the motor supply. it can be done, but you'll need a bit of skill.

for test purposes, at least, separate them. run the arduino on a 9V battery by itself.

if that solves it, you know where to look. if it doesnt, then you know it's not power.

divide and conquer!

[Anonymous No.394386]

>>393915

>hey guys,I have a problem
>when it draws under what it says it can supply,it works!
>but when it wants MORE than this thing says it can supply,it doesn't

Can you figure out what is wrong here,maybe?

[Bojangles No.395206]

>>394351
there are two motors, one on either side - will report later with what they are and voltage under load.

>>394353
i do not have an oscilloscope. i wrote the code, and thank you for the idea. i will implement this before the next update.

>>394375
more great input. thank you. i used a dremel to give access to the arduino's power input, but haven't used it because i couldn't think of why it would matter. the arduino will be powered via 9v upon next update.

>>394352
i think the voltage would drop, but i haven't measured it yet. the arduino itself can only put out about 50mA (if memory serves me correctly). the ardumoto board has on more than a few occasions handled excess of 4 amps even though it is only supposed to handle 2, so i don't think it has any limiting.

[Anonymous No.395214]

What is the 'c' rating on your battery?

[Bojangles No.395221]

>>395214
I'm not actually sure...

[Bojangles No.395223]

>>395214
but i will be switching to these in parallel as soon as i get the draw on the power limited to ~2 amps.

[Anonymous No.395280]

>>395223
One thing to understand is that if something isn't getting enough voltage it'll draw more amps, which leads (usually) to more heat. Since the motor is stalling it's drawing max current and just sitting there, making heat. I'm not an expert but it seems, to me, that you either have too much load or not enough wattage.