Options for auto leveling?

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dc42
Yes. A single beam is OK as a proximity sensor, but poor as a height monitoring device (which is what we need) because its sensitivity depends on how reflective the surface is. The RepRapPro Ormerod uses such a sensor, and you have to put white targets at the corners of the bed (which are the probing points). My differential IR sensor uses 2 beams to avoid that. So it works on a surface of plain glass, Kapton tape, glue etc. However, if the bed is transparent and the surface underneath is very reflective, the trigger height is affected a little by the reflection from behind the bed.

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TheBoilingDumpling
What if I used a single beam, but the bed was all white? I mean reflective for the beam? Wouldn't that be the same as using white targets at the corners of the bed, but you would be able to actually level around the whole bed in case it was not completely flat?

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TheBoilingDumpling

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nophead
Capacitive sensors detect insulators at a different distance to conductors. If you have an insulator over a conductor it will trigger at a bigger distance than either on their own. So if you have glass over metal it responds partly to the proximity of the metal and partly to the thickness and proximity of the glass, not to the top surface of the glass as you would want.

Capacitive, inductive, hall effect, and optical are all analogue measurements compared with a threshold. They can be affected by supply voltage, temperature and stray fields.

My preferred solution is a pair of gold contacts, you don't get much more digital than that. Pulled together by a magnet, pushed apart by a rod and pushed further to latch in an up position held by the magnet. The only electronics requires is a digital input pin.

You're talking about this right? [www.openbeamusa.com] I have seen a bunch of variation of auto leveling on Delta bots.