24v12 issues a safe start violation

Hi folks,

I’m using a 24v12 motor controller to drive a conventional brushed gear motor.
Control is done via serial using the Pololu protocol as described in the manual.
Everything is running fine (several identical units) for far, but one problem is still there:

Sometimes, while the motor is already running nicely for a few seconds, it suddenly stops, and the red error LED comes up.
Status register says “safe start violation”, but no other errors.
I did also look at the SMC center, which also has only the “safe start violation” error, but no other errors.
I can avoid that by letting the motor travelling at a slower speed, but I need the maximum speed.

Supply is a 6S LiPo battery (ca. 24V), current is well below 4 amps even at high speed.
The voltage only drops about 0.5V when the motor accelerates from zero to maximum, so there is no problem with the supply.
I o’scoped the rails, and they look fine and stable.
The 24v12 are in factory standard configuration (auto baud, safe start violation on etc) with the following exceptions:
I use analog input 1 to connect a potentiometer (which is mechanically connected to the gear motor, so allowing to get the exact position of the motor shaft),
and analog input 2 is configured a kill switch input.
I thought at first, that at higer motor power there may be some vibrations which triggers the kill switch (2 NC microswitches in series). So I disabled the kill switch feature, but the problem still persists.
Sometime it also the motor briefly stops, and immediately ramping up again, without issueing a safe start violation.
Does anyone have an idea what goes on here?

Have a nice day,

Hello, Wolferl.

I am sorry you are having problems with your Simple Motor Controller 24v12. As noted in the “Errors” section of the Simple Motor Controller User’s Guide, when in “Serial/USB” mode, the Safe start violation error occurs whenever any other error is stopping the motor. When that error has been fixed ,the Safe start violation error will remain until it is cleared. Could you post a screenshot of the “Status” tab of your Simple Motor Control Center after the error has occurred (before clearing any errors)?

Also, please note that the Simple Motor Controllers (SMC) do not directly support analog voltage feedback like you described. Are you using a separate microcontroller to poll the SMC for the analog inputs over TTL serial and process the feedback?