Final Implementation

The bulk of my time on this project was spent trying to build a transmitter. My assumption was that if I could simply generate a large enough signal, harnessing it would be the easy part. Unfortunately, I was not able to build an adequate transmitter and with the semester’s end rapidly approaching I chose to concentrate on building a working proof of concept model. In the end, my power source was a Sonicare toothbrush base. I built a demonstration model that consists of:

Receiving Coil
Rectification State
Power Storage Circuit
Mechanical Stage (demonstration)

The receiving coil contains two levels of windings of 24 AWG magnet wire. The lower level (closer to transmitter) has 50 windings and the upper has 10 windings. This coil has an alternating current induced in it that must be rectified. I used a classic four diode H-Bridge configuration to achieve rectification. The power level at this point is quite low, hence the necessity of the power storage circuit.

The circuit I used is a modified version of a circuit designed by Mark Tilden for use in low power robotics. It is called a Type 1 Solar Engine because it was intended for use in solar powered applications. The basic operation of this circuit is to charge a 4700uF capacitor from a low power source. When the voltage across the terminals of the capacitors exceeds a predetermined threshold set by zener diodes the circuit switches from charging to discharging.

In this application, the capacitor charges on the secondary coil and discharges into a small micro-cassette recorder motor. The cycle takes approximately one second creating a clock-like movement as the motor is pulsed. Finally, through a series of gears and a rubber pulley belt, a small image is rotated.