This is my small joule thief circuit with a 2N2222A transistor, a 1K resistor, a small bifilar coil and a single 1,2 volt rechargeable battery. In this video the circuit lights up 20 ultra bright 10mm LEDS and 4 bright 5mm LEDS, all in parallel.
At 1,28 Volt the total of 24 LEDS only draw about 60 mA while each single LED is rated for 3,4 Volts and 25 mA !!! That's what I call efficient.
The ferrite core with the small coil is recycled from an old PC power supply, all I did is that I added a second coil with 20 windings, I just wrapped the wire around the first coil.
It's an amazing circuit, very efficient. I was inspired by many people but the first video that I've watched about the joule thief was from Youtuber Lidmotor. Be sure to visit his channel, he has great videos.
Also check youtuber JohnnBlade