Hello, for my science project on the joule thief this year I ordered a 50 x 30 x 19mm toroid core. Is this too large? Will it work with a 1.5V battery? How many windings will I need. Thank you, and if you can, how many winding would I need of an input of 12V?

What material?

Ferrite

There are many ferrite grades out there.  What kind of ferrite?  The kind of ferrite and the dimensions of the core will tell us how much energy the core can store.  What oscillation frequency are you targeting?

Hello and welcome.

That is about 2" diameter and, if it is a decent permeability ferrite, you should have no problems.  When we all replicated the "Jeanna Circuit" we used toroids of high permeability that were almost 3.5" in dia.  We were getting about 700 volts from those.

The Jeanna Circuit calls for about 400 winds of magnet wire, and 2 other windings.  (A base coil and a pick-up coil)  All of these operated from "dead" AA batteries.  (Just one)  The transistors we used were TIP 3055's.  Google Jeanna Circuit and you will see my videos, Lidmotors videos, and Jeanna's videos on Youtube.

I do not know what what your final goal is here....how many leds do you want to light?  Or, do you want to light a cfl?  You do not need anywhere near 12 volts for any JT circuit like this to be able to make a lot of light.

If you just want to use your toroid to wind a "regular" bifilar JT using a small transistor like an 2n3904, with 1.5 volts or less input, it should work fine.  How many turns on the toroid?  If winding bifilar, I would use as many turns as you can fit on there with say...22 ga. insulated wire.  Be careful though, I would first try the circuit with a bunch of leds because the output could be pretty high.  (maybe 20-50 volts)

If you want high voltage, the Jeanna circuit can not be beat for simplicity and useful output.

Here is my Lidmotor's Jeanna circuit replication video:

https://www.youtube.com/watch?v=-m3sTtDbrPI

Let us know how you make out.

Bill

1. I have actually never found a toroid that did _not_ work in a JT circuit, with the right windings and other components. Powdered iron, ferrite, metal tape, you name it they will all work. Now, optimization is another story, as MarkE and Pirate will tell you.
I have used the teeny weeny toroids that you will find in the gutted corpses of CFL lightbulbs, I have used yellow-painted toroids from old PC power supplies, I have used special high-perm toroids ordered from the manufacturer, they all will work.

2. You do not even need a toroid at all! Cylindrical cores will also work and may be easier to find.

3. You can make the "basic" JT circuit with 13+13 turns on a low-perm ferrite toroid.

4. Check my video for how to wind a toroid without getting all flustered:
http://www.youtube.com/watch?v=ipfYPbNl_rc


My own favorite JT, which lights up _six_ NE-2s in series on a depleted AAA battery, uses a 2n3055 transistor and a cylindrical inductor salvaged from an old CRT monitor chassis, with an overwound "primary" on top of the stock winding. Not all 2n3055s will work, some are much better at HV than others (Thanks Bill for the handful of good ones!)


Some inspiration: