Motors Fail Test

Received the CNC back in March, I hooked up the electronics and had some difficulty with the left and right motors operating. Eventually I was able to get all three motors working and tested ok. The frame was finally completed yesterday. I reconnected the electronics to make sure all is working before taking the unit to the garage. And now the left and right motor failed test. Z motor works ever time. Any recommendations?

Hmmmm, the z-axis passing means it’s not a power issue…but having both the left and right motors stop working at the same time seems like a software issue not an issue with the Arduino shield because the left and right motors are driven by completely separate parts of the board.

Do the motors rotate and then the test prints failure (indicating an encoder issue), or do the motors not move at all?

What happens when you press one of the arrow buttons to move the machine?

Hi Bar,

Thanks for the quick response. Neither left or right motors move during testing. Ground Control indicates fail on those motors and no motion what so ever. I’m also unable to move the motor sprockets during calibration (I.E. 5 deg ccw, 5 deg cw, etc.) The unit has been connected to all three USB port with each connection yielding the same result.



Do the motors move if plugged into the z-axis (middle) socket? The z-axis panel should work even if nothing is calibrated. A chain motor should respond to the z-axis controls if it’s plugged in there. The problem could be the motors or the cable and this would begin to test those.

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Here are the steps I took:

After several attempts to get the motors working, I removed all the software from the PC I am using. Re-install the latest version of Arduino and Ground Control last night. No change, z motor functions fine and left/right motors nothing. Went to bed crying like a five year old. Read your post this morning and disconnected left/right cable as recommended. Placed the z cable/motor into port 1 and it worked. I placed z cable/motor into port 3 and it worked. Check continuity on both left/right cable, all good. Placed left cable/motor into port 1 and it worked. Placed right cable/motor into port 3 and it worked. Re-connected z cable/motor into port 2 and tested all motors, they worked. Not sure why. It may be possible when I checked the cables I pushed downward onto the connector terminals closing any gap issues. Still not sure, but it works. Thanks for your help.


Good troubleshooting! The connectors can be stiff when they’re new, that must be the cause. Thanks for the update.


I know this is a little older thread but looking for some help.

I set up the maslow and everything seems to be working but the z-axis fails the sensor test when I run it. The z-axis moves when I tell it too but no matter what I tell it to do it always changes direction. Meaning if I tell it to go up it turns one way, and if I tell it to go up again, it will change directions and rotate the opposite direction. I am using a motor from Amazon which other have used successfully as far as I have seen.

I have hooked up a X/Y axis motor to the z axis lead and it does not seem to have the problem and behaves normally. I did change the step count based on the encoder and gear ratio of the z-axis motor I purchased and have looked through all the settings that I can see would make a difference but, alas, it still does the same thing. Anyone had this issue before?

I am not sure of what to do to solve this issue. An ideas would be greatly appreciated.

Do the numbers on the zaxis readout change as the motor moves?

I am new to the Maslow so be kind…

I have just built the electronics (cobbled together a v1.2 board) from alternative parts using the documents on github and using motors acquired from amazon.

These reportedly have 11 ppr encoder, 280:1 gearbox and run at 14 rpm.

With everything connected both left and right motors fail testing. But both motors turn in both directions…

When i try to calibrate the motors they do half a turn when i press the 1 degree button in GC.

Any idea at to what settings need to be changed would be greatly appreciated.

This needs to be fixed before addressing calibration

if they are failing to calibrate, that means that the system is not seeing the
encoders changing as the motors are turning, what shows up in the log file?

we have found that our 290:1 gearboxes were not really 290:1 so I would suggest
opening your gearboxes and counting teeth on the gears to get the accurate count
(unless someone else has already done it for these motors). But this doesn’t
matter until the failing motor test is resolved.

David Lang

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Thanks for the quick response.

So “Failing” the test means no encoder data is reaching GC?

Given that I made the Arduino adaptor board it is quite possible I have made some wrong pin connections for the encoders.
Is there a pin definition file anywhere - the best I have been able to find is on Github:

But as both my motors go in both directions - I can assume for the moment I have the driver part correct.

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That is what I would guess is going on. It’s possible that the encoder wires are swapped also. If the motor measures movement in the wrong direction the test will fail so just swapping the encoder A and B channels is the first place I would start


The system.cpp in the firmware:

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What is the PCB version GC reports when you start?

Hi Gero,

Thanks for the links to pin definitions - very useful - software is not my thing.

GC is reporting pcb v1.2 (by not connecting any of the detect pins - fantastic)

I will study the pin definitions and get my multimeter out and report back.

Thanks a lot

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I double checked with my multimeter against the link posted by @Gero

But, as the motors are turning, and the leds are lighting on the encoders, the only connections I could have got wrong were the encoders.

Just swapping the encoder connections solved the problem - both motors just passed the test! Yay

Now I have the electronics working (most of which I had already) I need to get to work on the rest of the hardware. What is the best source of the sprockets and chains etc that will help support the community - without you guys this would not be a thing!


ANSI #25, pitch 0.25" (~6.35mm)
Is what your looking for.
Chain example:
10 ft
However for a 12ft motor distance you would need more (13-14) depending on how high your motors are over the sheet.
10 Tooth 8mm Bore Sprocket for #25 Chain like found here is what to look for:

No recommendation, just examples what to search for.


We should look at making it auto-detect the direction as part of this test.

David Lang


Was thinking the same thing.