- Joined Feb 13, 2012
Hi guys, I am writing a technical report on How to make a Joules Thief for my year 1 Engineering Literacy, in the report need to explain how it operates, please have a look it for me see if there is any error, thanks
- When the circuit is first switched on, the electronics current goes from positive of the battery to the resistor and to the secondary winding, and then goes through the base of the transistor, finally come out from the emitter of the transistor and goes back to the negative of the battery.
- Because the electrical property of the transistor, when there is a current flow from the base to the emitter, the collector and the emitter of the transistor will be start to switch on. The transistor here acts as an electronic switch.
- When the connection between the collector and the emitter electrically switch on, the can current goes from the positive of the battery to the primary winding and through the collector to emitter, then goes back to the negative of the battery, the winding connected to the collector of the transistor is call the primary winding;
- A positive voltage is induced in the secondary winding, which makes the connection between the collector and the emitter switch on harder;
- Depends of the material of the toroid, the ferrite saturates at some point, and the magnetic field stop increasing. The inductive current at the secondary winding stop increasing as the result of no magnetic field change in the primary winding;
- The reducing current through the base of the transistor drive the transistor staring to turn off the between the emitter and the collector;
- The magnetic field start to decrease and driving the current to the LED;
- The decreasing magnetic field induce an opposite current in the secondary winding, and turning the transistor off harder, and most of the current round to drive the LED;
- That's one cycle, and whole process repeat in hundreds and thousands time per second, its blinking so fast that its not noticeable to human eyes hence the LED looks like it's on all the time