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How to make Joule Thief with Multiple LED and maintaining its brightness. Answered

I've seen people running 61 LED or 100 LED on Joule Thief (1 AA Batt) with its full brightness. How did they do it??

I know how to build Joule Thief

I have:
-NPN   2N3904, 2N2222A, 2N4401   Transistors
-Resistor   what I have now 1K, 560, 100..
-Toroid 12 turns and 20 turns

Can anyone tell me what to do to run at least 10 LEDs with good or full brightness?


Where have you seen people running 61 LED or 100 LED on Joule Thief (1 AA Batt) with its full brightness? It seems a lot for 1 AA.


These are some videos

Joule Thief Light Box

Joule Thief..

19 LEDs joule thief

Radiant joule Thief

I cant find about Joule Thief with Secondary here..

First video
Not convincing. Looks like he's using a different circuit than a Joule thief, because there are a lot more components on the circuit board.
Third video.
Those LEDs are barely on at all.

Look for boosting switch mode power supplies for some ideas.


Convince yourself . Build one . I assure you we can light more than 400 leds blinding bright from a dead AA battery . Check out my builds . I light 110 Volt bulbs both led and CFL and Filament Bulbs with less than 5 volts
http://www.youtube.com/watch?v=dKCoV-0LXoY My pocketpower+ . Now going commercial

My ring Jt runs Lamps ,transformers just as bright as wall power for 24 hours + http://www.youtube.com/watch?v=3EPx7Zq46MI

Various House bulbs Run off a JT Circuit of 5 volts http://www.youtube.com/watch?v=8_0OsJUNlgw

The only way you'll do that is with something that ain't a AA battery.
You need to boost up to 120V to drive 100 LEDs !

There are better switchers that will start on 1.5V.

UNLESS you put them in parallel, in which you only need 2v, but a lot of current. Also you'd need ~200v to run 100 LEDs in series, since LEDs drop 2 volts each, not 1.2v. Also you'd likely blow the LEDs if you try to put 100 in series from all the current flowing through them (Remember, the current in a series circuit is the same for each component, the voltage drop in a parallel circuit is the same for each component, Kirchoffs law).

That won't change the power requirements however.


You are incorrect . I also build many 1.2 volt circuits , The Leds do not require "current" only Very High frequency Voltage. The Modifications Pirate and i made produce in excess of 1000 volts ata frequency over 200 kz and WILL LIght 400 leds very bright . That is a Fact .

That's what I just said, you'd need less voltage, but you'd still have to get heaps more current.

incidentally, LED drop depends on colour, small red leds typically drop 1.2 V, not 2.


Not true. I have videos on youtube showing 100, 200, 300, and 400 leds being lit by a JT circuit driven by an old AA battery. I also show 400 leds being lit by the JT circuit driven by my earth battery.

Name on youtube is the same as on here if interested.

Don't ask me to explain it, but pretty sure it can be done.

One approach is using Adafruit's Mintyboost 3. NOTE: the Mintyboost will work better with higher input voltages, but it will boost as low as 1V input to 5v output. (How many LEDs you'll be able to drive is a function of how much power can be pulled from your batteries... you can figure that out).

Another approach is Riad Wahby's "inara" circuit:
NOTE this design uses ONE 9V battery, and a pretty damn cool 555 circuit to drive 50 LEDs with minimal use of resistors (read the article to understand why that's a good thing). I've looked high and low for other (similar) 555 circuits for driving many LEDs, without any luck (all the 555 circuits I see use the 555 to blink. Blink is gaudy).

I'm looking to do something similar as you ask, but honestly, I wouldn't attempt this on less than 2AA (and most likely I'll use a 9V, or 4 rechargeable AA in sieries for 4.8V fully charged)

The reason you see "LED throwies" work with 1 small battery is because those coin cell batteries are actually 3V.

You can light more than one LED by putting them in series. That way, you need to supply a relatively big voltage (the voltage dropped across each LED times number of LEDs, so maybe 3v * 10 LEDs = 30V), but only at a current required to light a single LED since the same current is flowing through them all (so 10 to 24mA). The maths of lighting 60 LEDs is 60 * 3v = 180v at say 15mA = 2.7 watts; If derived from a 1.5v battery would be 2.7w / 1.5v = 1.8A. I'm not sure that a normal AA can delver 1.8A! Maybe they're driving them at a much lower current. Anyway, if you want to know more about how the circuit works, or you want to try it yourself, have a look at "Led torch circuit 2" on http://www.talkingelectronics.com/projects/LEDTorchCircuits/LEDTorchCircuits-P1.html. The circuit as it stands will light a couple of LEDs, but try adjusting the number of windings on the core, and perhaps using higher current transistors and you may be able to drive many more.