Instructables
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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.
 
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Joule thief no ic or toroid 08b.jpg

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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.

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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...

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Dave Kruschke (author)  julie.yoon.3761 month ago

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

kc8hps5 months ago

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

Dave Kruschke (author)  kc8hps3 months ago

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...

GreeceFallout5 months ago
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 !
Dave Kruschke (author) 9 months ago
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)...
Joule Thief mod # 1.jpgJoule Thief mod # 2.jpg
Dave Kruschke (author) 9 months ago
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)...
Joule Thief mod # 1.jpgJoule Thief mod # 2.jpg
Dave Kruschke (author) 1 year ago
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
iKeablr2 years ago
Hello nice writeup but you do know you can achieve this Joule Thief circuit with one Transistor and no Capacitor. Also the "Transformer" you claim not to use is an Inductor in the circuit you made. The only difference is that a person can easily make a Transformer rather than an Inductor and that the Inductor uses less space compared to a Transformer. I myself made an interesting Joule Thief only using one simple IC, a LED, and a source of energy above .5 volts. It can light up several LED's without any problems, too. I would show this circuitry but not a lot of people are into it even though it takes less room than any Joule Thief made so far.
Dave Kruschke (author)  iKeablr2 years ago
You have some good points. However, one of my main goals with my two "Joule Thief" projects was to find, test and share "Joule Thief" circuits that don't require bulky transformers that has to be wound by hand. In both projects, I used a cheap, "less than a dollar" inductor that comes ready made and is the size of a 1/2 watt resistor. I had thought that some readers might prefer this to winding a transformer.
Moreover, It sounds like you also might have a circuit ("simple IC and an LED") that meets my goal of not requiring a transformer...
Dave Kruschke (author)  acmefixer1 year ago
Other Instructable writers have mentioned "Joule Thiefs" that use two inductors side by side but didn't include more detailed information (i.e. dasimpson1981 on June 24th - Reverse Joule Thief Instructable).

Now comes acmefixer with a specific example of this "two inductor" circuit. But to try to learn more, we have to go to his "blog." I did this but found that acmefixer lacked the kindness (tenga la bondad) to reveal a schematic - a common annoyance found on more than a few blogs. Nevertheless, his description and picture revealed enough for me to plunk around on a protoboard with similar but not identical parts and produce a circuit that works. Acmefixer deserves praise here for "Going from the Word to the Deed."

So,... I may have successfully duplicated acmefixer's circuit. But no matter what, the circuit really worked great and also serves as a really good example of a working transformer where mutual inductance allows some energy from one inductor to be transferred to another nearby inductor. To assure some needed mutual inductance, I simply taped my two 330 uH inductors side by side.

From a Qualitative standpoint, acmefixer's circuit certainly meets my desire to avoid trying to break apart a CFL bulb to get a toroid that will probably need unwinding and rewinding - OR getting or winding a separate transformer. The side-by-side inductors seem to serve quite well as the transformer needed in this application. Moreover, all the parts are relatively cheap and available from well known US vendors.

From a Quantitative standpoint, I don't know if this circuit competes with a more conventional "Joule Thief" or the Chinese circuit in my Instructable, "Joule Thief" circuits, crude to modern. Perhaps this will be determined later.

In any case, the Chinese circuit still has the easy option of becoming a solar powered light by replacing the conventional battery with a rechargeable battery and then connecting a solar cell between pin 1 of the Chinese IC and the negative terminal of the rechargeable battery - the circuit currently used in some Chinese made "solar garden lights"...
Another Joule Thief 1.jpgAnother Joule Thief 2.jpgJoule Thief IC.jpg
Dave Kruschke (author)  acmefixer1 year ago
Why not just include the schematic in your reply here and save all of us the trouble of finding your schematic? As a simple example, I attached my "joule thief" schematic with the addition of a note that reveals the operating frequency to be 70 kHz. I bet you could do something like this.

Yeah, I put another 4.7 k resistor in series with the original 4.7 k resistor and the LED got brighter. Maybe the LED would have gotten brighter if I also had used 180 uH or even 100 uH inductors. But most of my enthusiasm here comes from the circuit simply working at all with such a variation in parts along with the weak coupling between the transformer coils. To me this means that this circuit is somewhat "robust" and might be friendly to readers trying to work with this circuit.

I don't understand the concern about the chokes having a DC resistance of less than 1 ohm. If we substitute in Ohm's Law, we get V = IxR = .070x1 = .07. Is a 7/100ths of a volt drop really going to make any kind of visible difference here? I agree that if the current was 1 amp instead of 7/100 amp, a 1 volt drop would have a noticeable effect on this circuit.

Finally, the two coils with mutual inductance are certainly behaving like a "transformer" in that some energy from one inductor is being surely transferred to the other inductor.


Another Joule Thief 3.jpg
Dave Kruschke (author)  acmefixer1 year ago
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A transformer is two inductors coupled together. They have different properties.
pandyaketan2 years ago
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
Dave Kruschke (author)  pandyaketan2 years ago
Thanks for sharing your Vedic blessing...
Dave Kruschke (author)  acmefixer2 years ago
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Dave Kruschke (author)  acmefixer2 years ago
For what it's worth, I've updated my profile to include my current age - 70. Your advice about "not letting a purist like yourself slow me down" is not needed as I've learned this many years ago.

Your use of "see the light" is not obviously defined to me. When you say "see the light," are you really referring to "Your Light?"

If "everyone" wants to use "joule thief" for the name of their "pet project" who, including yourself, is to stop them?

The use of "the name" joule thief is NOT "just a matter of definition" as definitions can radically change over time, i.e. 70 years in my case.

And as far as "winding a toroid for good practice for electronic assemby," I disagree. I wound toroids in a manufacturing assembly environment for one and a half years and it didn't teach me a thing about "electronic assembly."

I'm not sure what your agenda is but mine was to pass on some tested info about simpler ways of making something that behaves very much like a "Joule Thief," most especially my Instructable "Joule Thief" circuits, crude to modern...

Joule Thief IC.jpgSmall 330 uH Inductor.jpg