monitor packet serial with MotionStudio?

General discussion of using Roboclaw motor controllers
jameslo
Posts: 7
Joined: Thu Jul 11, 2019 10:03 am

Re: monitor packet serial with MotionStudio?

Post by jameslo » Tue Jul 23, 2019 5:47 am

I'm not understanding your recommendation about motor current settings. What value is the default value? I'm using Pololu 37D motors, and while their stall current is 5A, Pololu posts strong warnings about actually stalling the motor because that could damage it. So would this be an example of a motor that *can* damage itself?

I'm going to assume your bypass cap recommendation is for 0.01uF caps, which is the second scope trace I included. 0.1uF caps cause the rise time to be so slow the quadrature signals look like ramps, so I just assumed that that was unacceptable and didn't print scope captures for it.

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Basicmicro Support
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Joined: Thu Feb 26, 2015 9:45 pm

Re: monitor packet serial with MotionStudio?

Post by Basicmicro Support » Tue Jul 23, 2019 10:07 am

The 2x7A defaults to 15amps peak.

I was satying 2 things about current in my post.

1. Your motor cant damage this controller. Its just not possible under any normal conditions so setting a higher Blanking interval is safe.

2. But, I dont see any reason to set the current limit lower in your case. If your application was trying to limit the motors actual power then sure(eg setting a currrent limit below 5amps), adjust the current limit but you arent trying to do that(you are setitng it to 6amps which is higher than the motor can ever reach) so all you are doing by changing the current llimit is giving your self more headaches with no benefit.

Sorry. I missed read that about the scope trace. Yes, .01uf is the best choice for the signal lines under usual encoder speeds.

However .1uf also works in a lot of case. As long as the slopes arent so long that they break the phase order of the two signals it is perfectly usable and in some cases noise could be so bad that you have to use a larger cap. The larger the cap the slower the maximum encoder rate can be before you start having problems.

jameslo
Posts: 7
Joined: Thu Jul 11, 2019 10:03 am

Re: monitor packet serial with MotionStudio?

Post by jameslo » Wed Jul 24, 2019 5:36 am

Thanks for your clarification, I get it now. Also, I wanted to report back that those scope screen shots I posted are no good. I was grounding the probe too far upstream. When I ground it at one of the Roboclaw pins, the quadrature signal is noise-free.

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