Already early in the process regarding the electronics we thought it could be useful to implement a joule saver in the circuit. The intention using a joule saver is to keep the LED light even after stopping turning the handle. Therefore we chosen to incorporate a capacitor in the circuit.
Before we soldered the wires to the capacitor, we had to figure out how the specific capacitor worked (the capacitor we used is from Ikea’s Ljusa). We mapped the circuit which includes all the copper wires inside the PCB. The circuit of the capacitor is seen in the picture below.
To check the amount of voltage our system (which includes the DC generator, capacitor and the LED) needs to run we afterward tested the dynamo with some powertools and a voltmeter. The result of our experiment showed that the electronic circuit needed 4 volt to light the LED. During these tests, we discovered that our DC generator was broken. We were given a new, smaller one to replace it.
To ensure that our new generator was a DC generator and not an AC, we connected it to a voltmeter to find out. According to the waves on the screen, our assumption was correct – is was a DC generator.
To increase the voltage we connected a Joule thief to the circuit. A joule theif is a step-up voltage transformer based on the working mode of a pulse width modulation.
In this context it is relevant to mention, that there has to be a consistency between the joule thiefe’s inductance and the resistor. If so, the efficiency of the joule thief will be optimal. We have connected a wire, which works as an extra little resistor, on both sides of the original resistor. Doing this has increased the efficiency of the joule thief – we experienced therefore a brighter light from the LED.
Furthermore we have used heated isolationtape around the solderings to prevent a shortcurcuit.
As a final user interface we added a switch, which gives the user the possibility to store voltage (in the capacitor). Power the dynamo again using the switch and the LED lights without the user have to turn the handle.
– AR & KK