Pololu High-Power Motor Driver 36v20 CS FF2 goes high

I am building a Segway, and it’s begining to work pretty goed. But when I change direction fast the FF2 Flag goes high and the outputs are disabled.
The FF2 flag state tells me there was a short circuit. Reseting the controler is the solution.
But why does the driver indicate there is a short. And why does the driver think there is a short.
I am using a motor with a 30 amp stall current.
Thanks in advance.


How did you determine your motor’s stall current? What voltage are you running the motor at? I would expect a motor capable of being used in a Segway-type device to potentially have a much higher stall current than 30 A, and when you rapidly change direction you are attempting to draw almost twice the stall current, which the controller seems to be interpreting as a short circuit. You can probably get around this in software by implementing a short period of braking when changing from one direction to the other. You also might want to implement some software acceleration limits.

- Ben

Hello Ben,
Thanks for the reply.
I’am using 2 x 36 volt 800 watt brushed motors, and 2 drivers. At the moment I am running on 24 volt because I am still testing, I will increase this to 36 when I go outdoors.The specs say that the motor has a stall current of 30 amps. I agree with you that when I change direction the current is probably twice the stall current. As you suggest I will limit the current when changing direction.
But how does the board sense the short circuit? Is it the battery drop?


Are you sure the specs are listing 30 A as the stall current and not the rated current or peak efficiency current? Does it specifically say that the stall current is 30 A at 36 V? Can you link me to the specs?

I am not sure exactly what it’s doing internally to detect the short, but it might be triggering off the voltage drop on the driver outputs that occurs if they are shorted together.

- Ben