Overview
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This is a circuit that provides power for up to 4 infrared
emitter/phototransistor pairs. The photodiode current is converted to voltage
and low-pass filtered cutoff frequency approx. 150 Hz). Holes are designed for
a 4-40 screw (a common size in standoffs). The circuit is designed to work with
the OPS693 phototransistor LED/sensor matched pair. The 3D models of the food
hopper and nose-pokes are designed with the dimensions of the OPS693 in mind.
This requires a 5VDC power supply.

Assembly
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Design files generated using KiCAD. The Gerber files can be uploaded to a PCB
manufacturer such as Macrofab. Total cost for a fully assembled circuit from
Macrofab is roughly $15. Once the assembled board arrives, you'll need to
either solder wires directly to the holes or use 0.1" (2.54mm) pitch header
pins. The Pheonix MPT screw terminal blocks also work very well as they have
the same pin spacing.

License
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This project is licensed under the Creative Commons Attribution 4.0
International license.