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Motor Shield trouble
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Please be positive and constructive with your questions and comments.

Motor Shield trouble

by wireframewolf on Wed Mar 05, 2008 10:38 pm

EDIT: Disregard all the stuff I said before. I'm still having trouble with the motor shield I bought from adafruit, but after playing around with it a bit more and being of much clearer mind, I narrowed it down to the actual problems:

1. Regardless of the power source, motors 1 and 2 only get a small amount of voltage (about .30 volts max) using either a 9v battery on the shield's power supply or a 12v adapter on the arduino's power supply.

2. Motors 3 and 4 don't get any voltage at all.

The test motor is a motor rated for 12v but it runs fine on 9v.

So I'm trying to figure out what I might have fried to have caused this problem, because there are no visible bridges or bad connections. None of the caps look swollen, but if I fried the ICs it would be pretty much impossible to tell. However, maybe someone with better knowledge of circuits than me would be able to look at the schematic and the problems I'm having and point something out. Anyone have any clues?
wireframewolf
 
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by adafruit on Thu Mar 06, 2008 6:35 pm

post a photo of your current setup with the motors attached. its probably just a wiring problem
also, CAREFULLY read the 'powering' instructions here
http://www.ladyada.net/make/mshield/use.html

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by wireframewolf on Wed Mar 12, 2008 10:07 pm

Sorry I took so long to reply. Things got pretty hectic here. Anyway, the the general set up is 9v to shield, no power jumper, USB power for arduino (although to power the servos I need external power to the arduino, obviously). The Motor is hooked up to M2 in the picture. I'm getting ~9v across the power pins, and if I touch one lead to the positive power terminal and then to pins on the ICs, a lot of them about 8 something volts.

http://img502.imageshack.us/my.php?imag ... 690zn5.jpg

http://img340.imageshack.us/my.php?imag ... 691wx6.jpg

I order the explody components (anything I could have fried) again from Mouser ($7 in total) so if I did fry something, it should be okay when my friend resolders it for me. I really wish I could figure out a way to test the capacitors though, because I think one of the ceramic ones might be the problem.
wireframewolf
 
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by wireframewolf on Mon Mar 17, 2008 10:13 am

Okay, so it turns out my problem was that I'm stupid. Well, half of it was. I didn't know anything about amperage, except that it's current and it can kill you. But I did not realize that the motors I have draw what is probably more than 1 amp, even though they're rated for 12v. So I salvaged a much smaller motor, and was able to run it just fine.

The other half was that M3 and M4 are backwards relative to the AF_DCMotor(motor#, frequency) constructor in the AFMotor library. Meaning that motor(3, MOTOR34_64KHZ) actually sets up control for motor terminal 4, and motor(4, MOTOR34_64KHZ) sets up control for terminal 3. It's not a big deal to change it around in the lib code, but it confused the heck out of me and I can't seem to find mention of it on the site.

Anyway, is there some kind of wide threshold variable transistor I could use, hooked up to the terminal that I could run a seperate power source through to my larger motors?
wireframewolf
 
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Joined: Wed Mar 05, 2008 10:04 pm

by adafruit on Tue Mar 18, 2008 12:33 am

i will fix the timing variables, i made a mistake but i also have a few other fixes.
you can always connect a high voltage power source (up to 36v i believe) just for the motor drivers but the arduino cant take more than 16vdc so make sure you run them on seperate supplies
of course the chips themselves cant supply more than 1amp, but you can, in theory, wire them in parallel. i dont have any experience with that, tho

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Please be positive and constructive with your questions and comments.