Was hoping to be able to figure this one out myself however I’m officially out of ideas so I’m seeking ideas/suggestions. I can’t seem to get the Pololu Dual MC33926 Motor Driver Shield for Arduino to work at all. First off some background, basically building a automated gate using an arduino Mega and some ebay linear motors. Why, cause I can and it was cheaper than buying premade given I had to replace the old gate anyway. Was a good project to tinker with anyway. The project uses the MC33926 motor driver to drive the motor for each half of the gate and i’ve managed to isolate it down to this component and/or code as the cause of the issue.
I’ve soldered all the required connections as per the general motor driver configuration rather than the arduino stackable headers configuration. This was done to allow flexibility on pinouts for the Mega in the final device. Since I’ve been having issues I’ve gone back to my bench Arduino Uno to get the code/driver working then will test on the Mega with the updated pins. All the pins are as per the default/as if you used the stackable headers configuration on the bench test. Note that none of the jumpers have been connected as they aren’t needed given I’ve got flexibility with the jumper cables to choose whatever pin inputs I need. This includes the VDD/D2 jumper as well as ARDVIN=VOUT jumper as I supply the Arduino with power from elsewhere.
So what I have I done thus far to check it’s working. I’ve validated that the arduino is indeed outputting correctly using the default demo program by connecting some LED’s to the pins on the arduino which results in the following:
- D2 (always high as per program)
- M1DIR (high when going one direction, off for the other)
- M1PWM (fades on/off as PWM is adjusted regardless of direction)
- M2DIR (high when going one direction, off for the other)
- M2PWM (fades on/off as PWM is adjusted regardless of direction)
As such all of the above appear to be working as expected so the issue doesn’t appear to be with the code. When I connect all the pins (except VOUT as the arduino is powered via the DC plug) to the motor driver I tested the analogue outputs which seem to be more or less right. They aren’t perfectly zero all the times as they fluctuate a little however generally they’re OK and only reading up to a max of about 60mA with nothing connected to the M1 and M2 outputs. SF was tested by connecting from the motor driver straight to an LED rather than to the arduino. SF was always high but a bit dim when compared to the brightness of the LED’s tested above. Not sure why. It didn’t flag any faults on the arduino when running the program with everything connected despite nothing happening so I don’t think this is an issue.
When power is applied to the motor driver high current terminals the blue LED for MOT POW is on. Throughout all testing I’ve never seen the two LED’s near the motor driver outputs on. I tested a 12v LED and some 12v motors and these worked when connected directly to 12V supply however when connected to one of the motor outputs, nothing happens. Voltage at these outputs when testing remains at 0V. The high current supply is powered off the same supply that powers the DC plug for the arduino and as such shares a common ground.
I’ve also checked each jumper wire/soldered connection has good contact with the board. This was done with a multimeter between the arduino end of the jumper wire and the stackable header holes on the motor driver. All the Arduino side connections are fine. I haven’t checked the high current side to that extent as I’m not really sure where I can grab another point of these from. Measuring between the screw in the screw terminals and the non soldered part of each hole (given you have three hole options for the high current side) seems fine and shows good connection.
Any ideas, suggestions to try or anything would be appreciated as I’m really stuck on this one and feel as though I’ve run it to ground with no result or missed something really simple.
Tyler
Photos below for reference. I did drill a small hole in the opposite corner to the factory one for more secure mounting after confirming that these connections did not appear to be used for anything so I wasn’t damaging anything/shorting anything. Note the light gauge wires on the high current side are only for testing a low power LED to just get something to work.
