Driver Limiting Current During PWM Driving (MAX14870 Single Brushed DC Motor Driver Carrier; Pololu item #: 2961)

Using Pololu item #: 2961 (MAX14870 Single Brushed DC Motor Driver Carrier)

Running into an issue where the motor driver appears to limit the current after 4 or 5 seconds of driving a linear actuator. I have the PWM set at 200 Hz and have confirmed the input on a scope. Also scoped out the output to the motor and it also has this waveform in voltage (28 Volts). However, the driving speed starts out correctly and then the more it is driven the slower it goes. I can see the current from my power supply starting out at 700 mA…but then drops down to 35 mA after a few seconds and actuator barely moves. Have not cut the trace to go into automatic current limiting.


We have not heard of that kind of behavior from these drivers before. Can you post some scope captures and pictures of your setup? If you could post a video demonstrating the problem, that would also be useful. The forum does not allow users to post very large videos, but it does work well with videos linked from YouTube, so you could upload a video on YouTube (unlisted if you prefer) and link to it here.

Can you also tell me more about your linear actuator and power supply? A datasheet or link to where you got them would be ideal.

- Patrick