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Compact Opto Servo Probe - auto bed leveling

by atsnailpace Dec 21, 2018
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Hi, i made one, it works but it doesnt do auto bed leveling as it stops because the self test isn't succesfull, do I have to set it up as a custom probe? Can anyona share configuration.h with the correct settings? Im using anet a8 1.0 optiboot.

You have to set it as custom probe. The files attached are for Th3d Firmware for Anet 1.0 board. All commands related to servo are:


define SERVO0_PIN 29



define NUM_SERVOS 1

define Z_SERVO_ANGLES {10,90}

define SERVO_DELAY { 300 }


It is an Anet A9 and I suppose it is only bed dimension different.
Also the pin used for servo should be 27 for Anet A8. I used pin 29 due to the different LCD screen (12864).

Hi, thank you very much for the quick reply, i'm going to have a look, I forgot to mention that I'm on marlin 1.1.9. But i reckon it should be pretty much the same.

Very nice design. Please add a description of the different file versions.

Nothing special flag2 = flag for 2mm diameter rod, base3= base for 3mm rod.

Outstanding work. Thank You. Standard deviation is less than 10 microns with opto endswich, on my crappy BLTouch clone standard deviation was more than 100 microns !!!
For people looking for metal rod, just an idea, hss drill bit (broken if you have, or new one) cost less than few bucks. Put it in cordless drill and grind on bench grinder to make desired point tip.

How did You add LCD menuitem "Run M48 test" ?

Comment DISABLED(SLIM_1284P) in Marlin_main.cpp as in picture (pay attention to line number)

Wow, THANK YOU! That was fast!

Well thought out design. I advise, if possible, to replace the optocoupler. Instead of the TCST2103 usually installed in these sensors, it is better to use the TCST2300. Or at least TCST2202. The smaller the aperture of the receiver, the greater the accuracy of the sensor.


Thank you for the great project. Is there perhaps any possibility to share the source files?

I'm working on a similar idea with the servo higher up on top. Designed to fit in an 18mm round mount to replace a proximity. Yours is great, very compact. Love it. Great work.

Thank You!

Initially I did use the same configuration with a 40 mm rod without any degradation of accuracy. So in retracted position the total height was about 61mm. An adapted frame with a mount point below the actual frame could solve the problem.