Wireless conversion of Tormach passive touch probe using ATtiny85 generated Infrared beams

After being a user of the Tormach passive touch probe for several months on my PCNC 440 mill, I became used to its cable and found it no big deal- until I was recently able to outfit the mill with an Automatic Tool Changer. At that point I wanted to store the probe in the ATC where it could be automatically loaded and unloaded for use in probing cycles during CNC operations. That won’t work with a cable. There is a commercially available kit for conversion of the Tormach passive probe to wireless operation that I considered which seemed to be very robust and full featured but it was a bit of overkill for my needs so I decided to do a basic DIY version.

Video demo/build overview:


I chose an IR link rather than RF to simplify the implementation of a reliable short range connection. The design uses a 38KHz IR transmitter with the signal sourced by an Arduino compatible attiny85 pulsing high power IR LEDs using a transistor driver. The IR is received by a 38KHz IR receiver chip which uses a transistor to drive a reed relay operating in the Normally Closed mode used by Tormach passive probes. The NC relay contacts connect to the accessory input port of the mill.

The IR transmitter and receiver circuits are each powered by their own Lipo battery and associated USB Lipo charger module. The receiver circuit needs 5V, so its power circuit also includes a 5V boost regulator. The probe circuit has low standby power (.09ma) and wakes-up only on probe opening which should give very long probe battery life between recharges from 600maH Lipo probe battery. The IR Receiver standby of about .4ma should similarly provide long life between charges from 2500maH 18650 cell.


The schematics and 3D model (including Fusion 360 and STL format files) are found here:


The ATtiny85 code for this project is found here:



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