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Audible Frequency in Motor from MP6500

I have purchased multiple MP6500 carrier boards and plan on purchasing more if I can fix this issue I am having.

I have hooked up this board as seen in the recommended minimal wiring diagram on the product page. I am using a 12V. Power Supply. I am full stepping a 12V, 2A, Neema 17, bipolar, 1.8 step angle, Stepper Motor (Moons is the manufacturer - MS17HD6P4200).

Issue:
The motor when in a hold state (No rising edges on STEP pin) has a very whiny and annoying noise coming from the motor. In my application, I cannot have this. After attaching an oscilloscope to the input 12V power supply signal, it looked pretty clean and I don’t believe this is causing this audible signal frequency. Upon hooking up an oscilloscope to one of the motor output pins, there is a periodic sinusoidal 100Hz, 300mV PP waveform. Upon going through the datasheet, I am unable to diagnose why this signal is in the audible range. I understand why there should be a slightly varying signal in order to hold the stepper motor in place, but why is this in the audible range?

Also, I am trying to maximize the speed of the motor. So far I am only able to run the stepper motor at around 750 us - 800us a step before the motor stalls. Is this about as fast as I’m able to run a stepper motor? If you have any advice as far as configuration of the MP6500 to increase speed other than varying the potentiometer, please let me know.

Thanks,

Michael

Hi, Michael.

The frequency the MP6500 switches at is dependent on how quickly the current in the motor windings reaches the current limit, which is dependent on lots of factors in your individual system like motor inductance, input voltage, and (of course) current limit. You might try adjusting the limit slightly or changing your input voltage to see if that helps.

It looks like there is a torque speed curve available on the product page for your motor that shows how much torque is reasonable to expect at various speeds, so you should check that you are not too close to that limit. After that, there are several things you might be able to change, like increasing the input voltage, to help you step faster. This post by Ben has more suggestions.

-Claire