Piezo Disks for ABL with Marlin

[adamfilip]

Roxy

Do you know how difficult it would be to be able to use Piezo disks for Auto bed levelling?

http://www.thingiverse.com/thing:707392

[Roxy]

I don't know. But I can tell you what my concerns would be. The Piezo disk is always going to have some pressure on it. You would have to have the ability to set or null that pressure so you can see when the nozzle is touching the bed. And then to further complicate things, you may need to have Piezo disks at every mounting point because the further you get away from a disk, when you press down, it is going to take more pressure for it to show up at the Piezo disks that are far away.

It is an interesting idea... But the micro-switch legs that kick down do work pretty well.

[Alibert]

I like the idea.

'Nulling' the existing pressure can be done easily via the electronics. I think that with a well designed AC coupled input stage you will only 'see' the actual pulses (from the nozzle tapping the bed) and filter out any other (relatively constant) 'background' pressure (the DC and low-frequency part). With proper tuning to the dynamics of the tapping, you can potentially filter out a lot of background noise and vibrations.

[LuckyImperial]

Here's a whole kit, or at least something very similar.
http://www.ultibots.com/fsr-kit/

The hard part is getting multiple sensors to report a single response. The JohnSL controller is a custom piece that does it for you.

[adamfilip]

Here's a whole kit, or at least something very similar.
http://www.ultibots.com/fsr-kit/

The hard part is getting multiple sensors to report a single response. The JohnSL controller is a custom piece that does it for you.

Thats awesome.. will this kit work with Marlin??

[LuckyImperial]

Thats awesome.. will this kit work with Marlin??

It does. If I understand correctly (I don't own the kit) the JohnSL FSR Endstop Controller essentially makes it analogous to a normal mechanical endstop.

Here's one of the user's reviews though:
"Great kit. complete with everything you need. Install and configure my Big Delta. I currently use this version https://github.com/jcrocholl/Marlin the few changes. Excellent results with G29. Excellent shipping only 12 days from Florida to Italy."