Phase 2: Playing Electrical Engineer

Initial bench testing focused on powering and confirming control of motors via the HVAC unit. A wiring harness was prototyped using development board, soldering corresponding wires from the HVAC components to the control unit.

While the unit became operational, the subsequent testing proved extremely challenging as no attention was paid to probing individual connections while soldering.

The harness was remade then, with header pins to allow jumper wires to be connected to each wire leaving the HVAC unit.

This process introduced me to soldering and the basics of interpreting wiring diagrams.

Progressed continued towards reverse engineering the signaling protocols for each motor, the blower motor, and AC activation.

Initial progress was slow on an oscilloscope on campus, so a bench testing setup was constructed at home using a lawn mower battery as a power supply, and Arduino for data acquisition.

Once voltage dividers were set up, the Arduino enabled simultaneous monitoring of up to 5 connections at once. The Arduino scope proved to be an invaluable tool in reverse engineering the HVAC unit.