Hi all, I'm after a bit of advice please if someone would be so kind. I would like to replicate this circuit but first need to understand the workings of it, which I do not know, could someone please explain, particularly the 100 micro farad capacitor gets charged.

Thanks in advance, Arthur

 

It looks like the capacitor is charged by the battery. It looks like it's there (and the symbol is polarized) to provide 'instant' energy to the circuit because it can respond faster than the battery. This might give the 'pulse' a sharper leading edge.

 

Edit: The 100 uf capacitor is not even included in most instances of this circuit. It is relatively unimportant if your battery is in good shape.

I you look around the internet enough you can find a description of this circuit and learn the name of the inventor. I remember buying this circuit as a module back in about 1965, but I am sure it has been around a lot longer than that.

Attached is a more recent patent based on this circuit. In it one resistor is swapped out for an inductor to allow the circuit to generate a higher voltage. I think you will find that although the patent is not particularly easy reading it will explain the basics of the circuit.

 

It looks to me like the 100μF provides the pulse to the base of the PNP to create the one shot pulse when each magnet pole crosses the coil?
Which in turn turns on the NPN 1 shot.

 

Thanks guys, much appreciated. I have now replicate this circuit with success ! I am using a solar panel to power it but when the voltage goes over 1v the circuit stops working completely and the rotor comes to a complete stand still untill there is less sun. I don't get why ? Is there anything I can change in the circuit to fix this ? Thank-you.