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Hot L293D chips on the Motor shield
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Hot L293D chips on the Motor shield

by Orestes on Tue Sep 02, 2008 2:57 pm

Hi all,

I'm currently trying to use a M4SP-6NK stepper motor from an old printer with the motor shield. Unfortunately, the L293D chips are getting red hot - then I pull the motor PSU due to a bad case of chicken.

I've followed the instructions on http://ladyada.net/make/mshield/use.html as best I can, but I could be having a blonde moment, and would appreciate someone just having a look over what I'm doing... :D

I'm lucky, because there is some information on the 'tubes about this 4 wire stepper. Apparently, it's rated with a 10.8~13.2V working voltage at 400ma, 7.5 degrees per step.

I've got a benchtop regulated PSU (12v 2a) which I'm hooking up directly to the Motor Shield. The PWR jumper is open.
I have a PP3 9v battery powering the arduino (obviously with the jumper set to EXT).

I used my multimeter to group the two wires that show a resistance/connection (opposed to infinity) together, and connected them to port 2, leaving the middle connection open.

I figure that, doing it like this, I have a 50% chance of getting it right, as I should only have to swap two wires to have both coils going in the same direction. (this could be bad logic? :oops: )

I am using the stepper sketch from http://ladyada.net/make/mshield/use.html without modification.

Thing is, in any configuration of stepper motor wires, it results in very rapid heating of the L293D chip. (I have also tried the other chip just in case)


Anybody see what I'm doing wrong?

Thanks for your time!


orestes



EDIT Weirdness! It appears that my regulated 12v PSU is actually putting out 24V! I think that might explain it! Why would it be pumping out twice the voltage?!?!

Time for the bin, I think! :shock:
Orestes
 
Posts: 12
Joined: Sat Aug 30, 2008 5:14 pm

by adafruit on Tue Sep 02, 2008 3:02 pm

it should be OK...try running a small DC motor. or running it with different steppers, smaller ones. you could also try gluing a heat sink.

adafruit
 
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Joined: Thu Apr 06, 2006 4:21 pm
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by Orestes on Tue Sep 02, 2008 3:09 pm

ladyada wrote:it should be OK...try running a small DC motor. or running it with different steppers, smaller ones. you could also try gluing a heat sink.


Should I try and drop the voltage from 24v to 12v with a resistor first?
Orestes
 
Posts: 12
Joined: Sat Aug 30, 2008 5:14 pm

Please be positive and constructive with your questions and comments.