Hey! This thing is still a Work in Progress. Files, instructions, and other stuff might change!

Auto bed level (shown on Solidoodle 3)

by FadiK Jul 30, 2014
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I'm curious why you went from the hall effect sensor to the optical? The hall effect looked a lot simpler and easier.

Short answer, lack of components. I wanted it to get it done without buying a servo and hall effect sensor.

I had a printer (disassembled) lying around and I ended up finding those optical sensors and began my design around that.
Now the advantage of this design is the no servo which makes it lighter, frees up GPIO required for the servo control and it auto retracts as

I like your auto bed leveling probe because it is so light and relatively compact compared with the big, fat induction probes they have out there.
What exact optical switch can I use for this?
How precise is it?


Hi, and thanks for the compliment.
It is a regular opto-switch, I salvaged it from a relatively old inkjet printer. Actually the printer had 3 or 4 of them, some were easier to desolder and use than others.

As for precision, it is good enough.
I mean the nail is not 100% flat on its head and it does have a rotational movement while going up and down sometimes, so there
might be a factor of 0.Xmm of inaccuracy.

But all in all, this beats me having to calibrate it after each print or couple of prints.

Take a look at the cylinder printed, the elevation was as shown in one of the pictures, and that print came out very nice..


What firmware are you using for this, if I understand how this works shouldn't there be some sort of feedback to the firmware to adjust the bed during print?

illc0mm, no need for feedback except the one using the opto-switch which in turn notifies the printer-board as soon as the metal-nail crosses it's path.

Other than that, the Marlin firmware with auto bed level feature enabled, will take four points, to determine the slope that is affecting the bed (if any) and compensate for the variance in a linear fashion.

Nice job! I have a solidoodle 4 and am trying to do the same mod but am having some firmware issues. What version of Marlin are you using?

Late reply, just saw your comment.
Any solidoodle2/3 Marlin firmware that has the "auto bed probe" in it's configuration file and Read me should work :)
(sorry don't have the link handy atm)

How can I upgrade my Solidoodle 2 pro? Need a autobed leve

Having a Solidoodle 2 makes things easier as to my knowledge 2 & 3 are almost identical in the extruder design.
You need to print the parts and see how you can fit them on your assembly (if you have the stock acrylic holder).
I had the E3D MK5 when I did this mod, so I already printed lawsy's extruder mount.