Cooked My Motor Shield

Using Arduino Motors, Mechanics, Power and CNC
1

Hey guys,

I need help understanding how to power the Arduino with an external power source (non-USB). I have the following setup that works when connected to USB:

  • Uno R3 on bottom
  • Ethernet shield (using for the SD card slot) in the middle.
  • Motor shield on top
    Peripherals
  • Parallax Ping Sensor
  • CMPS03 (compass and I believe it has gyros in there too)
  • One small DC motor about an inch in length. It came inside an RC car I tore apart so I don't know what the specs are on it.

Anyway I plugged in a 9V to the screw-down Vin and GND terminals (Red to Vin and Black to GND) and got a lot more power to the motor as expected. I ignored the smell of things burning thinking there was just too much current going through the motor. After a short while I noticed that the motor shield was smoking and a piece of it was actually glowing red.

Surprisingly everything still works from what I can tell. Can someone tell me where I went wrong? I'll be happy to point out what part was glowing on a picture or provide further information if necessary.

Lesson learned. . . If it smells funny, shut it down immediately.

2

SlapYourBaby:
Surprisingly everything still works from what I can tell. Can someone tell me where I went wrong? I'll be happy to point out what part was glowing on a picture or provide further information if necessary.

What specific motor shield were you using? There are many different motor shield available these days, for example there are over twenty currently listed at Shieldlist.org . All motor shields serve a similar function, but the voltage and current levels they are intended to work with can vary.

3

Sorry about that. I am using the R3 Motor Shield on this site. Here is the link: http://arduino.cc/en/Main/ArduinoMotorShieldR3

4

OK, this shield shouldn't have any problems with 9 VDC, but it's not intended for a total current of 4 A or more than 2 A going through a channel (in your case the motor only needs one channel). What was supplying the voltage; a bench power supply, a wall wart, or one or more batteries? It would be helpful to know the maximum current that the supply can provide.

However even without that information, I think the motor could have been drawing ~2 A (or possibly more than that).

5

A lot of those small motors are 3vdc. The motor still spins freely or is it seized up? Without specs on the motor there's no telling. Pictures? Interesting that the motor driver chip got red hot without failing.