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Stepper Motor A4988

#1

I am using the A4988 and will like to know if there is anyway of detecting that the A4988 is driving the stepper motor to the maximum or minimum stop position. I believe when either limit is reached the stepper will have to generate a higher current to driver the motor against either stop position. Any suggestion on how to detect the stop position from the side of the microprocessor driving the a4988?
Thanks for the help.

Jose

#2

Hi Jose,
Thanks for posting on the Digikey tech forum. Can you provide the Digikey part number for the A4988 you are using, is it the IC or the stepper module. Have you tried measuring the current draw with a multimeter when the motor moves to max or minimum to see if there is a difference?

#3

Hi Steve,

Thank for you for replying to my query about this stepper controller. I am in the middle of the design process and have not tested with the module that we are using. I did read the spec and did not see any way to measure when the driver hits the max current which will occur when the stepper tries to driver beyond either the max or min direction. So I thought to ask just in case you guys have an answer.

I will be using the module you have, so is there a way to detected from the microprocessor side when the stepper is drawing too much current?

Regards,

Jose

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#4

Hi Jose, thanks for the reply. I don’t know of any specific way to measure at max current, did you read through this datasheet from Pololu, they have some good information on set up and current setting using the potentiometer on the board.

#5

HI Steve,

I read the chip spec so I will now read this doc from Pololu. Thanks for your help.

Regards,

Jose

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#6

Hi Jose,

The A4988 has no feedback pins to the MCU. Therefore, there will be no way for the A4988 to signal the MCU that it has hit any stop positions.

Using ADC pins from your microcontroller, you might be able to measure the voltage across the Rsense resistors and use that to surmise when it hits a stop position. However, due to the nature of the waveforms across the sense resistors, it may prove to be challenging to accurately measure those voltages. If you went this route, you would probably want to buffer the Rsense voltages with op-amps and then low-pass filter that signal.