For some reason, the Pololu G2 High-Power motor driver 18v25 seems to have a 30% dead on arrival rate. We’ve had multiple that when we plug in, it outputs 0V. We tested the OUTA and OUTB pins through the top of the connector, but it seems that some just read 0V once we plug it in.
We’ve isolated it to the motor driver itself since we found that we can fix the problem by just replacing the motor driver completely with no changes to the surrounding circuitry.
Is this a known issue? It reads 11V (the correct voltage) across all the components but reads 0 from OUTA to OUTB.
If anyone needs a picture, please let me know.
Thanks.
Hello.
We have not heard of issues like this from anyone else, and we test every unit we make, so it’s likely your problems are related to your setup. How many units have you had trouble with?
Can you post more details about how you are using your drivers, such as what power supply, motor, and microcontroller you are using them with? And yes, please do post some pictures of your setup that show all of your connections. Also, can you clarify what specific points you are probing on the boards when you say “it reads 11V across all the components”?
- Patrick
We have had issues with about 5-6 units now. Some are registering 0V when pwm is compared to ground even though we verified our microcontroller is sending out pwm signals, others are registering 0V on the OUTA and OUTB even though we verified it is receiving pwm signals and it is 2.7V (which sounds correct for pwm) and each capacitor and component leading up to the output pins are reading 11.3V. But when we measure the voltage output of the pins it is 0V compared to ground. We have checked motors and when we replace these with other units without changing anything in the setup there is no effect.
A side note, one of the big capacitors read 16V for some reason… we only are using a 11.1V supply and I don’t see any step up transformers or regulators for voltage…
Power supply is an 11.1V lipo battery (unregulated). Motors are the ones found on Amazon 12V 1000 rpm metal gear motors. We are providing pwm signals with analog write on a Teensy 4.1 and direction logic level signals with digitalwrite on the teensy.
I don’t have the setup with me right now, but I’ll make a post with a photo tomorrow.
What makes me think it’s probably a factory fault is that the bad ones don’t work at all when plugged in for the first time, and replacing them with another one without changing anything on the setup proves to fix all issues (assuming the replacement isn’t also dead).
This is our setup, we custom printed this PCB. It works with some of the drivers but others just appear dead on arrival.
It looks like there is a lot going on in your setup, so we should try to do as much as possible to isolate one driver at a time to get a better look at what is going on. Can you make a test setup separate from your PCB where you can power the problematic drivers directly with a power supply (no motor or microcontroller) one at a time? In that setup, please check the voltages on the following pins:
VM should be equal to your supply voltage3V3 (out) should be 3.3VnSLP should be around 5V
If all that looks good, can you use a jumper wire to connect 3V3 (out) to PWM and monitor the voltage across the driver outputs? Be VERY careful that you do not accidentally connect to the VM pin, which is right next to 3V3 (out).
For any drivers that do not behave as expected in that setup, please post a picture of the setup and close up pictures showing both sides of the board.
- Patrick
