Author Options:

I need help on my joule thief circuit that won't function. Answered

I've been attempting to construct a Joule thief circuit but it appears the circuit won't function, even with the essential parts that I scavenged from a CFL bulb. The parts are: 112dl transistor, LED, ferrite core, 1K ohm resistor, 1.2volt rechargeable AA battery and magnet wires, 14 turns on the core and  I attempts to switch the connections on the wires, it appears no hope. I've watched all the tutorial videos on YouTube but appears to be failure. If you found a solution to resolve this issue, please explain it specifically. Thanks !



Best Answer 5 years ago

Looks like you are wiring the toroid wrong. Kindly see the attached images for the details. Please note I may be wrong in judging your images.


It appears that I did it the wrong way, I follow the instructions on the image that you attached. Remains the same result, led didn't lit. The transistor I use is 112dl, apparently its a NPN.

I guess you will have to wait for the 3904 to arrive then.
It sucks to wait for a circuit which needs just 1 more part to complete!

Burn the coating off the magnetic wire and solder your connection.

Is it necessary to solder the connection? I burnt the magnetic wires before I finish the circuit.

Helps to ensure a good solid connection and rule out any issues with bad connections. If there is any other issue it will come down to the transistor. Whether you wired it right or whether its the right type to work in this manner. I prefer to use a common 2222npn.

The transistor in the initial CFL circuit its also NPN according to the datasheet. Will 2N3904 work on this ? Because I just ordered on amazon. Can you analyze the core to see if I did it right ? I appreciate your reply.

Everything looks fine. The 3904 may be a better transistor for this than what you already have.

I appreciate your reply, thanks for analyzing my circuit. I have the same feeling too, the 3904 is common for joule thief circuits. It's hard to find a NPN transistor that is compatible with the joule thief on my old powersupply. To save the time, I just order it online. One last question, will all magnet wires and ordinary wires work and is it necessary to solder the wires afterwards ? Because I am still a amateur on this, so I ask for further help on this website.

Any wire works in this circuit. Magnetic wire is primarily used in cases where many winding are needed and the tighter the winding are the better (i.e. transformers, motors speakers, ect.). Regular wires cane be used in the examples given but you can't get a good tight winding or as many turns when you have a thick rubber insulator in the way.

It's a good practice to solder all connections unless you have a good connector. Especailly if you intend to use the circuit often. Otherwise wires will fray, break, come apart or short the circuit. It's also a good idea to insulate any exposed wires. Either with heat shrink tubing, electrical tape, liquid electrical tape or a twist on cap.

Just one remark - any insulated wire works in the toroid transformer. If the magnet wire's insulation layer is damaged and allows a short, the circuit can't function.

If a multimeter is available, disconnect the transformer from the rest of the circuit, each wire end separately, and check that one end on each side of the winding only connects to one at the other side of the winding. And not all the other ends.

+1 for soldering. Alternatively or additionally check all connections with multimeter. Maybe the magnet wires insulator layer did not get removed properly?

check the circuit well.the emitter of transistor should be connected to negative or the shorter lead of led.and collector of transistor to the longer lead of led.then connect the base of transistor to the resistor.then attach the resistors other lead to one of the wires wrapped around the toroid.now attach the other wire to the positive lead of led.now take the battery and join the positive end to the end of the wire of the toroid where both the wires are twisted.then touch the negative lead of led to the negative end of battery.it should light if everything is ok.