Cannot get Duet 3 MB6HC and BLTouch working

dc42

@phat32, I'm glad you found the problem. Was it a genuine BLTouch, and if not, what brand was it? If we can identify the brand then I'll add a warning to your documentation about it. The genuine BLTouch manual is at https://5020dafe-17d8-4c4c-bf3b-914a8fdd5140.filesusr.com/ugd/f5a1c8_d40d077cf5c24918bd25b6524f649f11.pdf and clearly states the wire colours on the first page.

On Duet 3 and 3 Mini it's best not to enable pullup resistors on ioN.in pins. They all have permanent pullup resistors anyway, and if you enable the MCU ones as well then the noise margin is reduced.

droftarts

@phat32 Thanks for the wiki edit. I lightly amended it, also adding the colours. https://duet3d.dozuki.com/Wiki/Connecting_a_Z_probe#Section_BLTouch

Ian

Phat32

@droftarts Genuine as far as I can tell. Sadly when I tried to use the sensor to level it just drove the bed into the nozzle and would give the alarm flashing on the BLTouch. Pretty sure pumping 5V through the Z Probe killed something that is preventing it from sending a signal back.

And no problem This was an expensive lesson and I want to make sure others have the info needed to prevent it from happening to them

@Nuramori sadly my platform doesn't stop moving and drives into the nozzle and the BLTouch alarm activates. Oh well, lessons learned right? haha

@dc42 Thank you From all apperances and what not it appears to be genuine but in a Creality CR-10 V2 kit. I saw posts elsewhere of 2 others who had this happen, it could be the sellers and including alternate cabling or something.

Thank you! I thought that was the case but was unsure. I will make that change in the config It would be good if the RRF Config Tool can be updated when configuring the BLTouch on the Duet 3 to remove the pull up, if that is possible

Nuramori

@phat32 Do you have the correct offset from the nozzle? I've found the ideal distance to be 6.1mm from the nozzle tip to the flat base where the pin opening is. If it's too far away, then you can get the situation you're describing.

Nuramori

@dc42 Is the pullup info you mentioned also apply to toolboards? I had a devil of a time with my BLtouch until I enabled the pullup on the duet3 before I used a toolboard, and continued to use the pull up on the toolboard as a habit.

Nurgelrot

@dc42 You can't even trust real BLTouch I have one I know is genuine and the wiring was reversed in the small connector at the BLTouch. Always trace the wires.

Phat32

@nuramori Unfortunately it happened during the initial probe process, at that point the z offset doesn't really take effect. It will stop when the probe trigger is detected, the offset comes into effect when doing the print operation itself. To be safe I also set a very low initial offset so I can adjust from there

Nuramori

@phat32 I’m not talking about the g-code setting - I’m talking about the physical distance of the bltouch itself vertically from the tip. If it’s too far then the probe tip doesn’t move enough to trigger before the nozzle crashes.

Phat32

@nuramori Ah my misunderstanding, but also yes haha. The BLTouch when retracted is barely above the height of the nozzle

droftarts

@phat32 are the probes working now, despite miswiring? I thought they were quite robust, and as they run on 5V, miswiring shouldn’t make the magic smoke come out.

You should be able to test without actually homing, by sending M401 to deploy the probe, then lightly pushing in the probe pin, or moving bed up/nozzle down in small Z increments until it just pushes in the pin, and makes the red LED come on in the BLTouch. DWC should report a probe reading of 1000. If you push too hard you trigger the alarm mode on the BLTouch (flashing red LED); clear it with M42 P0 S160.

Ian

Phat32

@droftarts I can confirm the miswiring causes the z probe to not report back to the main board. I tried many times and while the probe would deploy it would not show any value in the UI but 0 when manually touched.

My 4th was just delivered and after swapping it out it worked perfectly instantly. With the wrong wires going to ground and the Z probe acting as the 5V had fired something for sure.

With the 2nd one I did 100% hear a pop when I issued the M401 command.