IR Bed Level Sensing?

Hi Guys

I'm still looking for the ideal way to sense the bed level/height has anyone tried the Sharp IR sensors?



I'm willing to put some effort into getting a working prototype but if others have tried it and discounted it I would appreciate some feedback.

Andy

Andy, I suggest you hop over to the Ormerod forum and ask about IR sensors there. Here is a brief history:

- RepRapPro released the Ormerod 1 with an IR Zprobe. The sensor used was a TCRT1000. It worked fine for RepRapPro, but not for me and others whose printers were either under halogen lights or exposed to bright sunlight. Both are strong sources of IR.

- I did a mod to the sensor board to modulate the IR and detect the change in received signal caused by the modulation. This reduced the sensitivity by a factor of 15 and later 30, and made the sensor usable. RepRapPro adopted this scheme in the sensor for the Ormerod 2.

- The modulated sensor is still sensitive to the reflectivity of the surface. On the Ormerod, white paper or tape is placed in the corners of the bed, and probing is only done over those white areas.

- I wanted a sensor that worked anywhere on the bed. I got ultrasonic sensing working, but it was rather temperature-sensitive. I also got capacitive sensing working, but that senses the bottom of the bed instead of the top, so it's not good if you swap glass beds between prints. I settled on a differential IR scheme, using two IR LEDs and one phototransistor. I've sold more than 100 of them to Ormerod owners. More details and a link to github can be found here [miscsolutions.wordpress.com]. One of my customers is using one of these boards on a delta.

I am considering making a smaller version of this board more suitable for delta printers. I am also resurrecting a design I had for a solenoid-activated mechanical probe, which would be easier to adapt to a range of delta printers with different effector heights.

Edited 1 time(s). Last edit at 02/04/2015 11:54AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

... check the datasheets for accuracy/resolution - if it's greater than 0.1mm, then forget it ...

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Viktor
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