Blown DC motor driver
February 05, 2009 08:49PM
I was testing my dc motor drive and I seem to have blown it. It ran for a while forward and backwards, then I heard a crack sound and it wouldn't work any more. I tested my resistance meter on the A+ to A- and there was no lights or anything. I tried this on the B+ and B- and the lights on the board lit up like they do when they are running. So I'm guessing I only blew the A section of the board. I can just swap the A wires for B and use the B side to run my extruder motor, but I'm worried about what caused this. I was running it on about 200RPM in the driver motor. The board itself looks fine, and I'm not sure where it was that I likely blew the board. Any ideas?
Re: Blown DC motor driver
February 05, 2009 10:21PM
Hi Peter,

Sorry to hear about your misfortune. I have two working DC boards here, which I used with a couple of different DC motors. Could you let me know what motor you tested the board with? While testing I put two 1 Ohm resistors in parallel to create a 0.5 ohm sense resistor in the power line to the driver board. This allowed me to do some rudimentary current measurement during the tests. I never used full power to the board, but at most a PWM ratio of 200/255. My fear was more for the motor than the board, as it was a 4.5V-6V motor.

I used a 7.5 V wall wart instead of a 12V PC supply. I could see how at 12V the motor could draw too much current for this relatively puny driver board. Probably it would be just a matter of plugging in a new chip for you, but otherwise you could make me an offer for an assembled and tested DC driver board smiling smiley

Re: Blown DC motor driver
February 09, 2009 01:26AM
I removed all my chips and noticed a change. While previously, passing a current into my B+ and B- caused my LED's to light up, doing it to the A+ and A- did not. Now the chips are removed, both the A+ and A- cause their pespective LED's to light up. I've replaced the chips with a new 74hc chip and no change from previously in the LED behaviour. I'm ordering in a few of the l29d chips and hopefull replacing them will fix it. That I was using the board and a power of 215 makes me worried about the general power demands of the motors.
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