# "Joule Thief" - No IC and No Transformer

48,694

87

23

## Introduction: "Joule Thief" - No IC and No Transformer

Yep, no transformer and no hard to get IC. But, ... two transistors and other parts are required. I actually found this circuit by accident while roaming Colin Mitchell's Talking Electronics website (talkingelectronics.com). This website is very rich with examples and explanations of a huge variety of circuits. In fact, this website is so abundant in circuits that later on, I couldn't find the circuit revealed here. Anyhow, I believe that the TE circuit can be considered "robust" as it works even if different parts are used.

### Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

## Step 2:

With an ordinary red LED in series with the white LED, the circuit draws 15 milliamps @ 48 kHz.
But when using only the white LED, the circuit draws 17 ma @ 38 kHz.

## Step 3:

The "Joule Thief" circuit using only easily found parts and no transformer might be attractive to many readers here. This is why I thought it was important to reveal this project.
But in my case, I am still tilted toward the simplicity of a "Joule Thief" circuit using little more than an IC and an Inductor, as revealed in my Instructable, "Joule Thief" Circuits - crude to modern...

50 5.2K
34 4.0K
178 11K

## 23 Discussions

My source voltage is 0.58 VDC and output needed is 3 VDC. Presumably the circuit will need to be modified?

I need your suggestion and help, from a source I am getting 100 mV and 50 microAmp (µA) not milliAmp (mA) current continuous mode. Can I use jewel thief circuit to light a LED. if yes please let me know the resistor in ohm, diode specification and led specification so that i can make the circuit and how many wire turns will be required. To enhance the density, can I use capacitor for this small production of what specification. Please help

I don't think that I have any specific answer to your question that will allow you to do what you are hoping to do. But I did make a 0.35 V power supply that you might easily make for further testing. I measured 0.35 V across each of the lower 1 k ohm resistors. When I loaded the lowest 1 k ohm resistor with a 10 K ohm load, the voltage across the middle resistor measured 0.36 V while the voltage across the lowest resistor measured 0.34 V. So,... a 10 k ohm resistor across the lowest resistor should draw about 34 u amps, according to Ohm's Law. This is all that I can offer you at this time. In the worst case, maybe you could show that 100 mV @ 50 uA is NOT a very practical power source...

Is it possible to replace Q2 with a Darlington type of transistor ?

What value of inductor should be used in case I want to power a 0.5W LED ?

Except for maybe the LED, all the related parts are cheap. Why not start with the parts that work on a regular 3 volt white LED and see what happens. I suspect (but don't know) that you might want a 100 uH inductor instead of 330 uH. Or you could consider putting two higher inductors in parallel to both lower the inductance and resistance. Since the LED isn't ON 100% of the time, you might get away with using parts with a less than 500 ma rating. I don't, however, see any advantage to using a Darlington pair. If I were doing this, I would just start trying things out...

Boost converter-y. Awesome.

can you give me exact circuit which you implanted on breadboard without ....and if possible please send me a jule thief ic

I am not sure of your question about "exact circuit." Did you read all of my Instructables related to joule thief?

You must give me your full name and mailing address for me to send you a joule thief ic. You can also try using my email address:
theabundance@yahoo.com to communicate with me.

Dave Kruschke

can you give me exact circuit which you implanted on breadboard without ....and if possible please send me a jule thief ic

can you give me exact circuit which you implanted on breadboard without ....and if possible please send me a jule thief ic

If you are interested in trying out the 5252F IC "joule thief" chip, I'll send you one for free. Just email your mail address to my email address: theabundance@yahoo.com

Hi Dave,

I have looked over and read you comments on the #2 circuit. You spoke about using 3 volts temporarily and found the LED or LED's were brighter. Im looking to light a few LED (more the better). would your circuit stand 3volts on a continuous basis? would I wire the LED's in series or parallel?

You will see my instructable about charging AA Alkalines. The unit is working flawlessly give it a look.

Luckily I have access to many "used/dead" AA's, my apartment complex has 350+ units and each unit has 2 AA in the carbon monoxide detectors. Thus I get as many as I wish. Im not sure how long that will last but I'd like to build a few Joule Thief circuits and use them up. Bryan

Thanks, Bryan. I would definitely start out by wiring the LEDs in series, not parallel. I believe that the "final" transistor is rated for about 1/2 watt. This would add up to powering a bunch of LEDs, provided the circuit continued to oscillate. I suspect that a modest amount of hands on trials would quickly answer your questions much better than my speculations...

Winding a toroid is really time consuming , so your instructable saved my day - literally ! - I made it in less than 1 minute and it's more efficient than my toroid based joule thief !

And now, I recently had a reader has ask me where I could put a photoresistor in the two transistor "joule thief" circuit to make the circuit turn off in light and turn on in darkness. I really didn't know but wired a photoresistor between the B plus and the base of the PNP transistor, Q1 (see first schematic below). This sort of worked but light didn't always shut of the LED - not good enough. I then added another transistor to turn on and off the circuit, where this transistor is controlled by the CsS Radio Shack style photocell and a 10k ohm pot (old volume control). This seemed to work fine as the light/dark trip point could be easily adjusted by the pot (see second schematic below)...

And now, I recently had a reader has ask me where I could put a photoresistor in the two transistor "joule thief" circuit to make the circuit turn off in light and turn on in darkness. I really didn't know but wired a photoresistor between the B plus and the base of the PNP transistor, Q1 (see first schematic below). This sort of worked but light didn't always shut of the LED - not good enough. I then added another transistor to turn on and off the circuit, where this transistor is controlled by the CsS Radio Shack style photocell and a 10k ohm pot (old volume control). This seemed to work fine as the light/dark trip point could be easily adjusted by the pot (see second schematic below)...

I recently had a request for info on how to run more than one LED off of the two transistor Talking Electronics circuit using only one 1.5 volt AA battery.

I didn't want to use a hook up with LEDs in parallel because I might have to use wasteful dropping resistors.

Actually I wanted to make my "new" circuit as much like the circuit from Talking Electronics that I had used for this Instructable.

I replaced the single LED with a string of 8 Green LEDs and they all lit up, but they were a little dimmer. So, at roughly 2 volts per LED, maybe the voltage supplied to the LED string was about 16 volts. I then connected a Red LED to the coil-transistor collector connection. I did this to make sure I had DC voltage to measure with my meter. The meter was connected to the free negative end of the LED and also the battery negative. I measured 14 plus volts here. And, if I add 1.6 volts for the Red LED voltage drop, I get pretty close to 16 volts DC.

Then I temporarily used 3 volts instead of just 1.5 volts for the battery power and all the LEDs lit up and were much brighter.

Finally, I disconnected all the green LEDs, installed the 1.5 volt battery and measured the voltage again and got over 21 volts. Adding 1.6 volts for the Red LED voltage drop, I might have a maximum voltage of 23 volts – just with one AA battery.

Dave

Bravo!!
Add my sensor version and you could have a free night light out of 'waste'!!

reg
ketan
-----
"May the good belong to all the people in the world.
May the rulers go by the path of justice.
May the best of men and their source always prove to be a blessing.
May all the world rejoice in happiness.
May rain come in time and plentifulness be on Earth.
May this world be free from suffering and the noble ones be free from fears"
---- Vedic blessing