ARES clubs week three

In week 3 we saw how a capacitor can store charge. Ethan is showing how a 10 Farad capacitor can light an LED, having been charged from a battery. 10 Farad is a large capacitor but in the oscillator circuit we used a 2.2 micro Farad capacitor, over a million times smaller!

To make an oscillator we used two transistors, each one switched on and off in turn. The timing of the oscillator was controlled by the capacitor and a 470 kilo ohm resistor as shown in the circuit.

Oscillator circuit

We constructed the circuit in stages, firstly with just the resistors and transistors, then the capacitors and LEDs and finally with the links.

“ it works!
It works!

If it didn’t work we would help one another.

“ mine worked, let me help you
Mine worked, let me help you.

We changed the resistor from the 470k to a 100k and saw that the timing was faster. We also saw that if the 2.2uF capacitor was changed to a 1uF it went twice as fast.

We worked out that if the resistance (470 000 ohms) was multiplied by the capacitance (2.2 / 1 000 000) it came out to be about one, which was roughly the time the LED was on.

You can download a 13 second clip of the oscillator here:

Working oscillator