Make a SUPER Joule Thief Light!





Introduction: Make a SUPER Joule Thief Light!

A joule thief is a simple circuit that can take 1.5 volts and put out as much as 5 volts. It can light an LED super bright! But have you ever heard about getting 120 volts out of a AA battery? The Super Joule Thief can do just that! It is perfect for lighting lights during power outages or just for a desk lamp. It can even charge cameras and cell phones! Watch the video for an overview.

I entered this instructable into the Make it Glow contest, so if you like it, please vote for me!! 

Step 1: The Parts

This circuit requires very few parts:
-TIP31 transistor [HAS to be a TIP31 because it works the BEST :) ]
-10k POT
-0.1uf-1uf capacitor (I used a .22uf)
-Ferrite toroid or rod
-20 to 30 feet of 30 gauge magnet wire
-3 feet of 22 gauge magnet wire
-heatsink? (Do you want to power it with more than 1.5 volts?)
-AA battery and holder
-AC output adapter (A 2 prong to 3 prong adapter works great)

Scissors, solder, and other tools will also help.

Step 2: The Circuit

UPDATE!! I changed the .22uf capacitor to a .68uf capacitor and I am getting a higher and more stable output.                                                                                                                                                                                                         Here is the circuit. As you can see, the transistor acts as an oscillator and pulses the current into the primary coil. This induces a large voltage into the secondary coil. The two prongs of the AC adapter can be connected to the ends of the secondary coil, or you can solder the ends to a light bulb directly. This setup has a 10 kilo-ohm potentiometer. This controls the current that flows to the base of the transistor. More current means a higher voltage in the secondary, and ultimately a brighter light.  The .22uf capacitor seemed to improve the output of my toroid, so I left it in. You may have to change the value depending on the resonant frequency of your toroid, or you can just omit it and the circuit will still work great. It is a very simple circuit as you can see.

Step 3: The Toroid Transformer

Let's take a minute to discuss the ferrite toroid. It does not have to be a toroid. If you open up a radio, you will find a ferrite rod inside that has a layer of wire on it. You can take off the wire and use that. Toroids take up less space and they also look nicer. There are several different kinds.

I used a black toroid from a 1983 television. Mine had a white plastic covering on it, so I popped it off. I found out that these toroids with the plastic covering are the best to use. If you would like to make a giant one, use a giant toroid. But the most common are one inch toroids.

They are also different colors. I have used yellow, black, and green, and these have all worked fine. But BEWARE! Some do not work as joule thiefs. It is best to make a normal joule thief and test if that works before doing all the work winding a secondary to find out that it does not resonate.

Step 4: Winding the Toroid Transformer

First, take some 22 gauge wire and wind 11-15 turns. Use a smaller amount for a smaller toroid, and a larger amount for a larger toroid. Cut the wire at the end of the 11-15 turns, leaving a few inches at the end. Scrape off the enamel coating on the ends of the wire. Next, take another piece of wire and twist it with one of the ends that you previously wound. Wind 4 more turns in the same direction. Cut the wire, leaving a couple inches at the end. Scrape off the enamel from the ends. Now you should have 3 connection points: a start, an end, and a center tap. The center tap is where you twisted the two wires together between the 11-15 turns and the 4 turns. This is your primary coil. 

It is a good idea to put a small amount or epoxy over your primary winding to keep it from sliding while you are winding the secondary.

Next, take some 30 gauge wire and start winding the secondary coil. You want to make one layer with the space remaining on the toroid. Then, start winding back over the layer you just wound. Keep doing this until you have around 200-300 turns. More turns = more voltage. I suggest that you wind 50 turns at a time, cut the wire, solder a new piece to it, and wind 50 more turns. This will keep the wire from knotting and breaking and will also let you take breaks without sacrificing coil output voltage. When you are finished, scrape the enamel from the two tips of the secondary and cover the whole toroid in a good layer of epoxy.

Step 5: Solder, Solder, Solder!

Now just put the circuit together based on the diagram!

Note what end of the primary connects to the collector, and what end goes to the potentiometer. The longer end will go to the collector.

If you want to get fancy and universal, connect the AC adapter to the secondary's output leads.

The toggle switch should go between the positive input and the center tap.

Step 6: Putting Everything Together

I epoxied everything onto a piece of perfboard. But feel free to get creative! If you wanted to, you could use a rechargeable AA battery and hook up a solar panel.


It can't kill you, but it is quite uncomfortable. 

Step 7: Using It!

Now find a light bulb less than 4 watts. LED bulbs work the best. I am using a 0.5 watt LED bulb and it lights up 2x brighter than it does in the wall. Plug it in and flick the switch! If you hear a faint high-pitch humming, it is just the transformer resonating. Use the potentiometer to dim the light if you want. The dimmer the light is, the longer the run time. The run time is about 2.5 hours with a fresh battery on full brightness.

You can use this ti charge cameras and phones too! But it is best used as a light.
If you have any questions, feel free to message me and I would be happy to help out.

Thanks for viewing my instructable and happy making!

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2 Questions

Center goes to the + 1, 5V. The bottom goes to the bottom of the pot, the left to B by TIP31. As yet I understand it.
My problem is the upper red (which says 350 t) and the right red (which says 200V) should also contact somewhere with it. Can You clarify something please, here I coming not out.

Would you be able to used this setup to power a very small electric car (one that is normally powered by a AA battery)


Neither end of the 350t coil is connected to the base of the transistor. If this was a slayer exciter then there would be a connection. However in this joule thief the 350t coil is free standing

If the 350t is free standing is, from where it gets than current to give 200V out?

or do you mean that the line 3507 is connected to the B of TIP31

i mean 350t and not 3507

Can this circuit be modified to power a larger LED? For instance a dimmable A19 size bulb, rated to use 9W@100mA maximum on line voltage (120VAC).

can i put 2N3055 transistor without putting the above one

Will it work if, a capacitor of 10f(with 2.7v rating) is used instead of 0.22uf capacitor that you have used in this project?

2017-07-15 20.18.31.jpg

I found two new MOSFET IRFZ44 would it be posible to make it work as oscillator?

Of course, Also I have my tiny 2n2222 as Oscillator, but this time I connected a ceramic capacitor labeled "224" between Collector and emitter, and the LED is bright constantly!!


is there a way to make a 13.4v version to jump start a car with a dead battery with (or similar) method?

3 replies

Unfortunately not with this circuit. You need something that could supply several amps and this circuit will supply a few milliamps at most.

I will buy the IP31 as you recommend, so I also wanna try to use several of this in parallel. I know that running transistors in parallel increases the power

When clevelandstorms says several amps he means around 650 cold cranking amps, meaning in cold temperatures. Car batteries are rated in Cold Cranking Starting Amps or CC: 650 CC or 700 CC for cold cranking amps.

Let's look at using an old standard 4 Watt 120 Volt night-light bulb. This bulb requires about 33 mA at 120 Volts. The circuit we make would still have to supply 4W but, from your 1.5V battery, which means about 2.67 AMPS of current. Which, to say the least, is requiring far more than we normally require from a single AA battery! The thing to remember is POWER, how many Watts does it take? P=I*E or in words, Power (Watts) = Current (Amps) times (*) Electromotive force (Volts) so 4W = I * 1.5V => 4W / 1.5 V = 2.67 Amps yet at 120 Volts 4W / 120V = 0.033 Amps or 33mA. This means to get the 33mA at 120Volts the 1.5 Volt battery (if supplying 1.5 volts) needs to supply about 2.67 Amps of current, and as the voltage drops the battery has to supply MORE current to produce the same power, Watts, to keep the bulb going.

Simply stated, to use this circuit to run an LED night light is, sort of, counter productive. Don't get me wrong, this is a wonderful demonstration of running a very small 120Volt device from a 1.5 Volt battery. But, if all we want is a night light, then using the standard Joule Thief circuit without that large coil (with its shock hazard) to simply run an ultra bright 3V LED directly would be far more efficient. You'll get about a week or more of operation from a dead (~ 1.2 Volt) AA battery instead of only 2.5 hours on a new AA battery for the 120Volt LED night light. It would be the same for charging a cell phone, if we could do it directly with a simple Joule Thief we'd get far more power transferred to the phone battery and far less power wasted just running the conversion circuits.

Cool! I haven't made it yet, but I have all of the parts. I am planning to make this circuit with the core on which a CRT tv deflection coil was wound. You're right though; taking off the copper wire absolutely SUCKS! I have been at it for a while, and I still have this much left:

6 replies

Wire gauge isn't critical. I used 22 for the primary and 30 for the secondary.

So Wire gauge isn't Critical?, If found some info and and Amperage/AWG table that said that If you want more amperage to support a heavy load, you need to use a wire with more gauge.

In my opinion, Might be I'm wrong

Does the wire need a heavy coating? I have 24 AWG wire, but it is coated with enamel instead of heavy insulation. Is that okay?

Yes definitely you want to use enameled wire

For the tape, sure. I think that would work, just be sure to cover it smoothly. As for the windings, I don't really know. I guess keep the 4 + 15 for the primary and do a few hundred for the secondary. I would do the secondary first, winding it all the way around the toroid covering it completely in one layer, then go back over the secondary with some insulated wire and wind the 4 + 15 primary.

By the way: is there a particular wire gauge I have to use?