Motion controller Overcurrent problem

General discussion of the MCP motion controller product line
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richardtech
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Joined: Mon Jun 15, 2020 11:26 pm

Motion controller Overcurrent problem

Post by richardtech » Mon Jun 15, 2020 11:47 pm

Im a student working for a project using a MCP230A to control two Graphite Brushes 200 Watt maxon motors. The problem I'm encountering is that when we use the Basic Micro studio to send a PWM signal, the motors don't move. The software will alert with OC (over current) and we will observe a current draw of 2A, even when we stop sending the pwm signal. The current draw will only stop when we power cycle the controller.

We borrowed a MCP233 from a different project and swapped it out to test with the exact same settings. Everything seems to work fine, so we think that our circuit and motors should be fine. The only other difference we observed was that the Logic Battery showed consistently close to 5V on the MCP233, while on the MCP230A it would vary between 0.7 to 2V.

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

Re: Motion controller Overcurrent problem

Post by Basicmicro Support » Tue Jun 16, 2020 8:27 am

1. If one board works and the other does not that would indicate a problem with the one that is not working.
2. The MCP230A was the original model of the MCP23X family. It is similar too but not the same as the MCP233 models.

So either the MCP230A you have is damaged(have you tried running other motors besides the Maxons) or it specifically doesnt like running the Maxon motors.

Some Maxon motors are very low inductance and should not be used with any MCP controllers. Make sure the coil inductance is atleast 100mciroHenries. If it is less the motor is designed to be used with 60khz motor drivers. MCP is 20khz.

The current shunt circuit has evolved over time on the MCP line. The new boards are better than the older ones. It is possible the MCP230A is getting false over current readings and wont let you run the motor. You can try increasing the Current Blanking window. It defaults to 2.6%(assuming you are using the latest firmware and Motion Studio software). You can increase it up to 20% but I recommend increasing in 1 to 2% increments and testing. Find the point when the false overcurrents go away.

But make sure you are not trying to use the 60khz maxon motors. They will destroy any of our motor controllers eventually if you try.

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