SMC05A - How To Tell If the Driver Is Blown

I have built a system with an SMC05A, and based on correct feedback (blinking green LEDs) have correctly programming it to run dual motor (I have it connected to a Tamiya 70168 double gearbox as that’s a recommended combo on the web site.)

I have written a program which ramps each motor speed up and down as a test, and the LEDs for each motor turn on in succession as expected (green for forward, red for reverse.) I have placed a 0.1 uF ceramic capacitor across each motor as advised, then connected the motors (with a 9-Pin D-Shell Connector for quick disconnect). The LEDs continue to perform as expected, but the motors do not give any indication of life.

Is there a single electronic test that can give an indication whether or not the drivers are blown. (I have tried to be careful, but I am a novice may have made a boo boo.) I have access to a logic analyzer, a meter and in a pinch I have a friend with a scope.

Possibly relevant info: So far I have not tried to run the motors faster than 1/4 of maximum speed (32 out of 127). I have 4x AA batteries connected to the motor power input, and input voltage is about 6.4V.


If the LEDs on the driver are working but the motor outputs are not, the driver is probably damaged. Have you tried looking at the outputs with a multimeter?

You mentioned that you were only running the motors up to 1/4 of their max speed, which corresponds a motor voltage of about 1.6V. That voltage might be too low to get the motors to move. Could you try running the motors at a higher speed?


I tried running the motors at full speed and I’m getting nothing.

I put a resistive load across the outputs from the driver board at the suggestion of an EE friend of mine and measured zero volts. I assume I somehow blew the drivers, so I’ve ordered a replacement.

Thanks for your help.