Encoded motor recommendations

Questions about using encoders with the Roboclaw product line
robof
Posts: 36
Joined: Tue Jun 27, 2017 11:21 pm
Re: Encoded motor recommendations

Post by robof »

acidtech wrote:Currently removing the snubber cap(s) is the best option if you feel comfortable doing it but if not please check back next week.
Just checking back this week, per your comment from last week.

Are you by chance doing some testing specifically with the servo city encoders?
User avatar
Basicmicro Support
Posts: 1594
Joined: Thu Feb 26, 2015 9:45 pm
Re: Encoded motor recommendations

Post by Basicmicro Support »

I got new motors from Servo city to test and I now have another method to work around the noise issue from the snubber.

Change the Roboclaw PWM mode to Sign magnitude using Ion Studio(remember to save the setting). Then add .01uf caps from each encoder signal wire to ground. This creates a very simple low pass filter which elliminated the noise fromt he snubber circuit.

On the larger HD motors it was completely gone. On the smaller motors all the postiive noise was gone. There was still some negative but the Roboclaw has protection diodes on its I/Os which clamp this to less than .7v and it doesnt effect the encoder reading so you can ignore it.

Note this only works if PWM is set to Sign Magnitude. Locked Antiphase will generate more than twice as much noise which cant be easily filtered out(I havent found any way to do it yet at this point).

We are planning on change our default PWM drive method to Sign Magnitude on all new units in the future. Some models already default to it.

Post Reply