A4988 Stepper Motor Driver DOA

I just purchased a A4988 Stepper Motor Driver Carrier with Voltage Regulators and cant seem to get it working correctly.

I have attached how i have it wired.



I am using a Gecko G540, using terminals 5&6 for output.
There is a step down regulator set to 12v and I adjusted the current to 0.5v using the REF pin to ground on the motor driver board.

The motor is energized (wont easly rotate). I have tested STEP and DIR for the output on the G540 and it is working correctly.

How can i go about getting a replacement?

Hello gregsilver,

I am sorry that you are having trouble with your stepper motor driver. It does not sound like the board is dead/damaged.

I am not familiar with the Gecko G540; however, it looks like it is also a stepper motor driver. What is the role of the A4988 in your setup?

You mentioned that your STEP and DIR outputs are working; what voltages are you reading from them? Since you have jumpered your logic voltage, VDD, to 5V, the STEP and DIR outputs will need to be 5V digital signals as well.

Additionally, while it looks like you are correctly connecting the STEP and DIR pins, it also looks like you are not connecting the GND pin for these voltage signals from your Gecko board. This is shown as one of the minimal wiring connections in the diagram featured under the section entitled “Using the driver” on the product page:

pololu.com/catalog/product/1183

I am using the driver as a 5th axis for an extruder.
The ground is a common ground being used from the power supply powering the gecko drive and the step down regulator. I have tested all ground pins for continuity across the purchased board and there is no need for a seperation ground. I have tested continuity from the lpt port on the pc sending step and dir signal, also having a shared ground.

I am also seeing 5v on the step and dir pins.
The gecko just passes pins 1 and 17 to output terminals, untouched.
I have multiple steppers to test and they are all working when using a different single motor board. I want to use the popolu board because of the current limiting.

What are you using to generate the signals that are passed through via pins 1 and 17? If they are just passed through, why go through the Gecko at all? The G540 datasheet makes it seem like OUTPUT 1 and OUTPUT 2 are open drain outputs, which would leave them either floating or grounded depending on the input control signals. How are you getting the STEP and DIR pins up to 5V? Can you send us a picture of your whole setup?

A picture of the entire setup isnt going to solve anything. Everything is using standard insulated wires. (IE: Printer cable from PC to Gecko G540)

So the photo I attached, is the best for what is going on.

The OUTPUT 1 & 2 is driven via MACH3. The settings are correct. Again, I have tested another driver board and it resulted in a working configuration.

Mach3 is set to use Pin 17 & 1 for Step/Dir, which generates the required signals TO terminal 5&6 on the Gecko. I am using this setup because its the least complicated method. I dont want to make a breakout board just to get 2 pins from the LPT cable into the additional motor controller board.

I am getting 5v because that is what a typical voltage coming from a LPT/PC port is.

When testing (again this works with other boards…but stating it here to show you have have tested everything) I measured the signals using a multimeter for step and dir AT the pins on the pololu board. When jogging the axis I was getting a reading for step. When I changed direction, it would drop to 0v or 5v, depending what direction it was going. All correct.

Can I just be sent a replacement already? This type of support is very…very…slow, and I have done my due diligence on testing. The part is defective.

Since you seem to be indicating that the driver outputs are functional and the IC is outputting a valid reference voltage, the board does not seem defective. Additionally, we test all of our boards before we ship them, so it is unlikely that you received a damaged device.

I would be happy to continue trying to figure out what might be going wrong (e.g. have you verified that you have a good solder connection on your step pin?), but it sounds like you are in a rush for a resolution. I will contact you by email with options for getting a replacement.

By the way, what were the other boards that worked in place of the A4988 driver?

I have on hand some TB6560 based controllers. Also an arduino that i have reading 2 input pins via serial.

have you verified that you have a good solder connection on your step pin?

Yes. I have also tested at pin 16 and 19 on the IC itself to make sure it was getting to the chip. This was based off the schematic posted on this site.

Im just going to order another board and be done with this. This has cost me more than the $20.00 in wasted time posting on the forum. If i get the same results with the new board, i will let you know. However…if it works… i would appreciate a refund.