Single endstop switch worked, now misbehaving

Mostly Printed CNC - MPCNC Troubleshooting
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I finished the build for my CNC last week using a brand new Rambo board from V1. I ran two successful test cuts, with all X Y and Z homing working correctly.

Then suddenly yesterday, I start a cut and the X axis tries to tear itself apart. After a decent amount of troubleshooting, I found one of the two endstops (X0 if you’re curious) must be reporting as triggered because it doesn’t move at all during a home operation. (If I turn off soft endstops, both motors move just fine via LCD, so it’s not a motor issue.)

I had some switches from a previous project, so I tested swapping the X0 switch, but the same behavior remains. I ran a project without X homing, but left Y homing on and it worked fine.

I saw some notes in the forums about trying a firmware update to handle noise, but I’m not sure if a firmware change is the right answer when just one endstop is at issue and didn’t start that way. Are there any other suggestions?

2

Which board?

Check endstop functionality with M119. You can use repetier host from a computer or the terminal if you have the touch screen.

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This board https://shop.v1engineering.com/collections/parts/products/rambo-v1-3l Using the firmware Ryan flashed it with - Marlin with Dual Endstops

I have a LCD on it. It’s hard to get a computer to it right now, but I can try tonight

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As I feared, X0 is reporting triggered…

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Sounds like a wiring issue. Does it change to open when you press it?

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I was finally able to get a Pi on my build so I could check this more easily. It reports triggered regardless of if it’s engaged or not. The other switches change their status correctly.

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It should be wired at the switch on the C and NC. The resistance should be zero when it isn’t pressed. On my desk test rig, I check things by just jumpering across the S and - pins (do not short the +!)

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As far as I can tell, it’s all wired correctly. I have all 4 switches on NC and tested using a different switch I have (also wired NC) and it behaved the same. I don’t have the supplies to jumper it today, but that’s a good next step. I’m betting, if there’s not a defect in my board, that the wires to the one switch broke sometime after that first run. I could try terminating with a new dupont connector next

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The little red jumpers it came with work great for jumpering it. I would just unplug it first, so you don’t accidentally tap that +5V pin with them.

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Mine didn’t come with any jumpers. I guess Ryan doesn’t include them on the ones he ships out. I’ll have to find or make one soon

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I made a jumper and it did correctly register the circuit as closed. It’s not the board, but the wire or the connectors to the switch. Guess I’ll have to make a new wire for that limit switch

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In the end, the wire wasn’t broken, the connection between the switch cable and the extension had come loose, even though it was liberally electrical taped.

I unhooked all the wiring, rerouted the cables as I had been meaning to do, and re-secured all the connections between the motors, switches, and extensions. Since then, I haven’t had any issues with homing.

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