Current Limiting Measurement

General discussion of using Roboclaw motor controllers
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cpmcgowan28
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Joined: Wed Jun 19, 2019 5:58 pm

Current Limiting Measurement

Post by cpmcgowan28 » Sat Jun 22, 2019 12:01 pm

Hello,

I apologize if this is addressed in the user manual, but I read through it and I couldn't find anything. I was looking into using the Roboclaw's current limit feature, but I'm not sure which current the Roboclaw is limiting. Does it limit the current through the motor to this value, or the supply current (motor current time duty cycle)?

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Basicmicro Support
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Re: Current Limiting Measurement

Post by Basicmicro Support » Mon Jun 24, 2019 10:14 am

It limits the current to the motor individually on each motor channel. Basically its a simple PI controller on the current reading with blanking for low duty cycles(eg turns of current limiting on low duty cycles).

cpmcgowan28
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Joined: Wed Jun 19, 2019 5:58 pm

Re: Current Limiting Measurement

Post by cpmcgowan28 » Mon Jun 24, 2019 8:10 pm

To clarify, it is measuring the current flowing through the motor, correct? Not the equivalent current coming from the power source?

So if for instance I had a motor drawing 20A running at a 50% duty cycle and the limit was set for 15A, it would measure this as 20A rather than 10 and trigger the current limiting?

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Basicmicro Support
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Re: Current Limiting Measurement

Post by Basicmicro Support » Tue Jun 25, 2019 10:19 am

Correct, It is measuring the current through each motor(two current shunts). Duty cycle on the motor only matters because we need to be able to take a clean reading. At very low duty you can't get a clean current reading(hence the blanking setting). The measurement is of the actual current through the motor.

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