Genesis XL 1.5 X2 motor vibrates but doesn't rotate smoothly

It seems that either there is some kind of power delivery problem from the farmduino to the motor or there is a problem with the X2 stepper motor cable. I would have just replaced the cables but they have been out of stock.

I bought the Genesis XL 1.5 in early 2020. After getting it set up the gantry would move smoothly along the X axis and then stall about halfway down the track. Unfortunately, life got in the way and it has sat unpowered until this spring. I realigned and squared up the tracks, and reflashed the SD card with the latest version before powering it on. When I powered on the Farmbot the X1 motor rotates like it should, but the X2 motor just vibrates back and forth and never really rotates correctly. No matter what I try the problem follows the X2 cables. I’ve watched the video on troubleshooting X axis movement, but that didn’t seem to help.

I noticed the power light on the RPi was not constantly on. In my experience this indicates low voltage to the RPi. Reading through the forums I saw that this seemed to be a problem with some v1.5s. I checked the voltage on the pins and was getting 4.4v. I replaced the OEM USB cable with a known good USB cable and the reading increased to 4.8v. Now the power light on the RPi stays on.

I disconnected the drive belts for most of the troubleshooting.

Things I have tried:

  • Disable encoders on X axis
  • Increase voltage to X motors
  • Verified that motors were correctly inverted
  • Swap X1 and X2 stepper motors
  • Swap X1 and X2 cables on the farmduino so that X1 is now in X2 and vice versa
  • Connect X2 cables to X1 motor
  • Connect Y encoder and motor cables on the farmduino to X2 headers on farmduino - when I tell X to move the Y axis moves smoothly
  • Replaced extension cords with beefier cords

Farmbot version is v15.2.1

Here is a video of the problem:

Any insight into what I should check next would be greatly appreciated.

You didn’t say if swapping the motors and cables for the X2 motor moved the problem to the other X motor, or whether the problem stayed with the X2 motor. If the problem stayed with the X2 motor, it must be the driver on the board. If the problem moved to the other X motor, then it has to be the motor or the cable.

…of course, you’d be making sure that the encoder cable was swapped from the X1 motor to the X2 motor, at the same time as the motor driver cables were swapped.

When I connected the X2 cables to the X1 motor, the problem moved to the X1 motor. I thought it might be the driver on the board, but the X1 motor worked when being driven by the X2 driver.

So, to clarify, for my ‘hard of thinking’ you left the X2 cables connected to their normal positions on the board and then swapped motors? (X2 cable and encoder moved to X1 motor)?

Yes, that was one of the things I tried. When I moved the X1 motor to the X2 position the problem stayed with the X2 cables.

Just to clarify, my fault finding procedure would be as follows:

  • Initial problem X2 motor not turning smoothly, (even under no load).
    1/ Swap plugs for X1 and X2 cables and encoders on main board - if the problem swaps to the X1 motor, then it is being caused by the cables, or the board.
    2/ If the X2 motor is still misbehaving, it is caused by the motor.
    3/ Assuming the problem isn’t isolated yet and the results of a cable swap are causing the X1 motor to vibrate, you then need to swap the cables from the X1 motor to the cables from the X2 motor, leaving the connectors on the board swapped as in step 1/.
    4/ If the problem is fixed with the X1 motor, its is being caused by the cable. If the problem with the X1 motor vibrating is still there, it is caused by the board.

If the issue moves motors based on the cables used, carefully examine the connectors on the ends of the cables for damage, (this is the most common point of failure), if you know how to use a multi meter to check continuity do so. Also check that the cables have the same colored wires connected to the same ends of the cable, using the working cable as a model.

It appears to be the X2 cable. I completely swapped the X2 cables with the Y cables and farmbot moved along the X axis. Y stopped working. Now I just need to find replacement cables since the store is out of stock. Do you know if it’s possible to get replacement cables that will work for that motor?

Now that you know it is the X2 cable, it should be relatively easy to fix the cable. If you don’t feel confident repairing it, take the faulty cable and the good working X1 cable, to your local electronics store and ask them to either fix it, or to recommend someone who can. A cable is V easy to fix.

I don’t know of any suppliers of Farmbot cables, other than Farmbot.

First of all, very nice job on finding the faulty part. Sometimes the thin wires on those connectors break or the metal insert in the connector that is only held in place by some kind of plastic hook got pushed out of the connectors case. Maybe you can already see anything wrong on the connector?

I was not able to find a direct replacement probably because the wire length of 2.3m is not that usual in common devices like 3d printers where these motors are mostly used, but you could try to fix your cable as dmbgo mentioned. I’m suspecting a faulty connection on the motor side of the cable. So you could get yourself a short 4pin 2.54 Dupont to 6pin hx2.54 cable like this
and solder the white connector to the old defective X2 cable. If that did not work, you can also do the same on the other end of the cable.

Afterall you probably want an official replacement for that cable. Maybe @Marc can provide more information if there will be a restock of that cable soon? :slight_smile:

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Thanks for the help. I will give it a go and see if I can fix it. Marc said that the cables should be back in stock around mid June. Unfortunately I need the farmbot up and going before then.

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They should be back in stock in the next few weeks. Check back in mid June and you will likely see them in our online store.

Alternatively, if you are handy, you can take a multi-meter and check the continuity of each conductor and determine which one is the broken conductor. Just check the continuity of each color wire. You should be able to determine exactly which conductor is broken.

How to test for continuity

The likely failure point is the point at which the copper wire conductor is connected to the metal portion of the connector. Determine which cable is broken, cut it and strip the wire back to the conductor and with a soldering iron, solder the broken conductor back onto the connector.

This video shows how to do soldering and is meant for conceptual purposes only. Your actual repair procedure may look different than this.

Marc from FarmBot

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