Micro-Powered Solar Cell Oscillator with Speaker

This project is the same as Micro-Power Solar Cell Oscillator in Oscillator section, modified to power a Speaker at the output.

The characteristics are very similar, so we will only suggest some experiments for you to try. The circuit will work without the two added Capacitors, but these are included to make the tone more pleasant.

As with the Earphone circuit, you can connect the Meter in series with the Solar Cell to measure total current. Connect it so that the 3.3uF bypasses the Solar Cell and Meter.

In order to measure the current at high light intensities, parallel the Meter with a 470 ohm Resistor. This makes the full-scale Meter calibration about 600uA, because at full-scale 250uA goes through the Meter and 350uA goes through the 470 ohm Resistor.

The same Meter-shunting concept can be used with other Resistors in the kit, or that you have in your "junk box". The highest full-scale current reading you can get using the Resistors in the kit is about 2mA when using the 100 ohm Resistor.

The formulas to use for other Resistors or currents are as follows:

RS is the Meter shunting resistance in ohms and IT is the new full-scale current calibration in milliamperes (mA).