However the shutting of T1 instantaneously also releases the primary winding and restores it to original condition so that the supply voltage now can pass across to the base of T1. The above situation switches OFF the voltage across the secondary winding triggering a reverse emf from the coil which is effectively dumped across the connected LED. T1 switches ON and pulls the entire supply voltage to ground and in the course chokes the current across the primary winding of the coil so that the biasing to T2 dries up, shutting off T1 instantaneously. When the circuit is switched ON, T1 receives a biasing trigger via R1 and the associated primary winding of TR1. If you find the circuit connections to be alright yet the LED not illuminating, just interchange the coil winding terminals (either the primary ends or the secondary ends) this would fix the problem immediately. If everything is done correctly, connecting a 1.5 V penlight cell would instantly illuminate the attached 1 watt LED very brightly. In fact any ferrite core will, a ferrite rod or bar will also serve the purpose well.Īfter this is done, its all about fixing the parts in the shown manner.
About twenty turns on each side will be quite enough.
The coil may be wound over a T13 torroidal ferrite core using a 0.2mm or 0.3mm super enameled copper wire.