Roboclaw Minimum Overcurrent Limit

General discussion of using Roboclaw motor controllers
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eng101
Posts: 6
Joined: Fri Sep 21, 2018 5:58 am
Roboclaw Minimum Overcurrent Limit

Post by eng101 »

I seem to be unable to set a current limit at or below 5A with a 15A Roboclaw. Is this expected? If I set a 5A current limit it immediately throws the overcurrent fault even with no motor running or connected.

The stall current of my motor is 20A but the running current with the load we have is far below that. I need to be able to detect a stall condition before it trips my power supply overcurrent (which is 5A).
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Basicmicro Support
Posts: 1594
Joined: Thu Feb 26, 2015 9:45 pm
Re: Roboclaw Minimum Overcurrent Limit

Post by Basicmicro Support »

1. Motor current isnt equal to battery/power supply current most of the time. Current at the supply is equal to Motor Current * duty cycle. So 50% duty with a motor current of 10amps would equal 5amps at the supply.

3. You should be able to set down to a couple amps. Setting a 5a limit should be ok. However the current sense is subject to noise. If the power supply is noisy that could explain the reason its giving a false over current.

In most cases with power supplies, to fully use your power supply and get the most out of your motor(s) you do NOT want to use a current limit. What you want is to set a minimum voltage limit. When the power supply reaches its maximum current its voltage will start to dip. If you set a minimum voltage limit to 1 to 2v below the power supply voltage(how low you can set this will depend on the power supply) then the Roboclaw will automatically free wheel when in this under voltage condition.

Also, If you are going to use a power supply you need to use a voltage clamp circuit like the one described in the user manual. If you dont you risk producing high voltages due to regen(power supply do not sink regen) which can damage the Roboclaw and/or the power supply. Set your maximum voltage to 1 to 2v aboce the power supply voltage. When enabled the voltage clamp will activate when the voltage reaches 1v above the maximum voltage limit. Note if you do not enable a voltasge clamp then the Roboclaw will try to protect itself from high voltages by braking the motors.

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