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