Cannot Get Gantry to Home

I have a Blue and White K40 40W laser. I bought the Cohesion 3D board, installed it, and it will not home. The firmware is Smoothie running on a dedicated Windows 10 laptop. USB cable is the one supplied with the C3D board.

From what I can ascertain, when everything is working the gantry should move to the upper left to “home” itself and 0,0 or 200,0 the coordinates and set it up to work. It doesn’t home itself no matter what I try. I turn it on and click home and it moves to the right and that’s it. When I click Origin, it crashes into the gantry and grinds until it stops. I’ve updated the firmware numerous times, changed bed size in firmware and in Lightburn, but nothing works. I’ve put off asking for help until now because I am completely confused.

This may be a good starting point for you:

Pictures of your board and wiring will also help.

So I used the M119 function. Doesn’t matter where the Gantry is X, Y, and Z all show as “1”. When I used my Nano board the switches worked fine (they are proximity sensors). So I doubt that it’s the switches. My end-stop plug only plugs into one slot on the board so I’m wondering if I have a bad board seeing as how it is reading a closed switch on the Z axis which doesn’t even have a switch.

So I reverted back to my M2 Nano board just to see. When I plugged it in it auto homed to the back left corner and both of my proximity sensors activated (turned red) indicating that it knew where the gantry was. With the C3D board the sensors never even turned on when I manually set the gantry to the back left corner. So I know the sensors work and I had it plugged into the correct location on the board, so I can only assume the board is defective.

The fact that you have inductive homing sensors is actually an extremely important detail. Most machines have physical limit switches. We have only seen inductive sensors a handful of times and the machine and wiring has been different each time.

Makes sense, based on previous experiences this is because of differences in wiring and certain protections that the C3D board has that the M2Nano does not.

Again, please provide pictures of the machine, the sensors, and all the wiring up to and including the board.

Once we have those we can take a look and guide you through the solution.

Ok here are some pictures. I’ve removed the panel so the board is sitting funny (not plugged into power). Hopefully this will assist in solving this issue.

Andrew, thanks for the photos.

The area of interest is the 2 brown wires that then get joined to a single olive green? wire that runs inside the wire wrap near the large power plug. I have a suspicion that it will run through the wrap and back to the LPSU.

Please trace it, and provide those details and pictures of the LPSU connections, or of other relevant areas if I’m off here.

I have seen this before and have a pretty good idea of what needs to happen next, but I would just like to be sure.

So I traced the two brown wires that are heat shrunk (sp?) together. They run into another brown wire that I traced back to the LPSU to what appears to be the 5V output (where the large red wire is going to) Please see the attached photo.

Okay, the brown wires we originally traced are going to 5v on the LPSU, which is good, because it shows the inductive homing sensors can run off 5v. You’ll want to grab some photos of the labels on the sensors so that we can see if they are capable of/ meant to run at a higher voltage such as 24v, or if they are actually made to run at 5v specifically.

You’ll need to disconnect that line we have traced from the LPSU end so that you can connect the brown wires from the sensors to 5v on the LaserBoard. You could tap into the 5v available on any one of the endstop headers on the bottom row of the board, either with a crimp connector, or just with a female “dupont jumper wire”.

Sensors are rated 5V-30V.

Stupid question, but can I simply cut the brown wire going into the LPSU and then solder an end onto it that would go to the positive side of one of the endstops? That should solve this issue correct?

Yes, that is what "tap with a female dupont jumper wire” meant.

Here is an unrelated pic that shows it:

Well after getting everything soldered up and cleaned up I finally tested… and…

SUCCESS!!! It now homes automatically upon startup and everything seems to be working perfectly. Thanks so much to everyone for their input. I would sticky this post for anyone that has proximity sensors and how to fix.

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Sweet. Yeah, this (inductive sensors) has come up about 5 times out of over a thousand of boards, and each time it has been a different machine with different wiring. Sometimes they connect the sensor to 24v, sometimes to 5v, sometimes to 5v because that’s all the M2Nano can handle but the sensor is capable of 24v (and other times it’s only capable of 5v), and lots more fun.

We’re going to add a documentation article about inductive sensors hopefully soon.

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