Recycling a Robin Nano board to build a 3D printer using an old computer PSU (300 W), it only boots on when I have no endstops pugged in at all or if I trigger all the ones I have plugged. At the moment I release them the screen goes off (but the fan of the PSU is still on). Does anyone have any clue about what's going on ?

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    $\begingroup$ Welcome to 3dPrinting.SE! What controller are you using? Have you double checked to ensure you've attached everything correctly? Have you tried it without anything plugged in (no endstops or motors)? $\endgroup$ – Pᴀᴜʟsᴛᴇʀ2 Oct 20 '19 at 18:59
  • $\begingroup$ I doubled and tripled check the wiring. When nothing is plugged it goes on properly. Controller board is a Robin nano board. $\endgroup$ – Cobactan Oct 20 '19 at 19:15
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    $\begingroup$ Sounds like the endstop switches are shorting VCC to GND when not pressed. I guess the logic board has its own 5V regulator because I imagine the computer PSU would happily melt cabling or weld the switches. $\endgroup$ – r_ahlskog Oct 20 '19 at 19:30
  • $\begingroup$ I used the nano board previously on a printer with a 24 v psu without any endstops related issues. The nano is supposed to manage both 24 and 12 volts. I doubled checked on the endstops boards to make sure signal, ground and VCC are corresponding. $\endgroup$ – Cobactan Oct 20 '19 at 19:35
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    $\begingroup$ @R_asidkog your comment is good. It may not be right, but it is good. I can't upvote it because it is not an "answer". Could you submit it as an answer? $\endgroup$ – cmm Nov 22 '19 at 4:16

From your fault description of printer logic board losing power when endstops are released it sounds to me like those endstops are shorting VCC to GND when not pressed. That the fault also goes away when the endstops are unplugged reinforces this.

I guess the logic board has its own protected regulator because otherwise you would be shorting out the power supply and that would also turn itself off after likely causing a lot of damage to the logic board.

  • $\begingroup$ Thanks for posting your answer! Much appreciated! $\endgroup$ – 0scar Nov 22 '19 at 14:50

It ended up I had like super cheap endstops that were actually shorting VCC to GND, as suspected by r_ahlskog. Just bought other ones and now it's working fine.

  • $\begingroup$ Thanks for posting your answer and referring to @r_ahlskog! You may accept it after 48 hours, but it would be nice if r_ahlskog posted the answer so you can accept that one. I'll ping r_ahlskog to post an answer! $\endgroup$ – 0scar Nov 22 '19 at 13:57
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    $\begingroup$ I'm starting to think that those switches were just wired wrong for your printer. Should I try and edit in that into my answer. $\endgroup$ – r_ahlskog Nov 22 '19 at 14:19
  • $\begingroup$ it is relevant in context qith this question if your endstops are NO or NC. It sounds they are NC. $\endgroup$ – Trish Nov 22 '19 at 23:19

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