I built the simple Joule thief.
Parts: - Transistor : 2N2309 - 1 pc - Rezistor: 1 K/ 0.5 W - 1 pc - LED: white, 5 mm - 1 pc - torroid core, 1 cm diameter, white ferrite - 1 pc - cables- 0.5 mm D: 2 pcs @ 30 cm each, blue and white - minibreadboard - 1 pc - Battery NiMH AAA, 1.2V - 1 pc (alternatively: pile AA, exhausted)
Now it comes the strange part: a slightly larger blue torroid core, of 2 cm D, 80 cm wrap same wires did not work. I went down to 40 cm wraps - no chance LED did not light.
In one example it was a picture of a blue ferrite ring - looking quite the same I used and did not work.
Searching for ferrite cores I found tons of info about a zilion types of ferrite rings but nothing clear about what the colors mean. Somewhere I found that some types have more permeability than the others, which sounds somehow trivial.
Supposing I will end up with a suitable more efficient circuit, then how I can be sure I can order the same type of ferrite cores?
Thank you very much for any tip, kind guidance or pointing to a more friendly web-site!