Progress

This week, I finalized the layout for the prototype version of our PCB, and made a more functional prototype of the gearbox for the kinetic energy harvesting. The gearbox does spin and has minimal friction. However, the gear ratio is too high, so too much force is required to get the motor to start spinning. This means that even after attaching external weights, the motor would not spin when swung. Fortunately, the design is parametric, so I can experiment with less aggressive gear ratios, which will make it easier for the weight to turn the motor. Just spinning it a quarter-rotation by hand fairly slowly, I could already get 2 volts, so there is plenty of margin to make the gear ratio lower. We only need about 600mV for the energy harvesting to work.

Pacing

This PCB should have been ordered over Spring Break, but unfortunately there were several difficulties with part selection, having to create custom symbols and footprints, and having to learn how to do impedance control on a trace. Fortunately we can still do our testing on a breadboard; I will focus on getting efficiency from the energy harvesting while the board is being manufactured.

Planning

Next week, I need to:

• Get a gearbox that spins under its own weight
• Measure performance numbers for the energy harvesting strategies