Make Your Own Joule Thief!

[@stmounts]

I've made several of these circuits using a toroid out of a CFL and various NPN transistors. The last one used a 1W white LED and two AA cells, works great even with cells down to 0.5V. Today I tried using an original germanium OC75 fom the 1960's, a PNP. Of course you have to modify the circuit to use a PNP transistor, basically you just reverse the battery and the LED, everything else is the same. I thought the germanium transistor would work better as it has a much lower turn-on or forward base-emitter voltage than silicon transistors. Anyway, it didn't work and I suspect the reason was the collector current rating of the OC75 was too low to reach saturation of the toroid core. If the core doesn't saturate, the circuit won't oscillate.

[@Filippos_77]

can I use BC548 transistor or Lm35 transistor???

[@stmounts]

@@Filippos_77 A BC548 will work.

[@fredflintstone1]

very nice and well executed simple project

[@abeditani8293]

About the coil . Is the middle tap is from end and starting from the two line ? Explain it more because you cut the end of 2 line and make it not same as the picture you draw

[@SimpleElectronics]

if you look closely, by cutting and soldering it, you make it exactly like the drawing buty with two opposing windings

[@gartmorn]

@@SimpleElectronics yes I think if I remember correctly that the coils have to be opposing so you can't just tin the joined end as the coils would then have the same polarity. Hope that makes sense. I'm no expert!

[@SimpleElectronics]

@@gartmorn That's exactly it!

[@Filippos_77]

can I use BC548 transistor or Lm35 transistor???

[@MrToni99]

Very good explained... Thank you.

[@Filippos_77]

can I use BC548 transistor or Lm35 transistor???

[@SimpleElectronics]

should be fine, give it a shot!

[@Filippos_77]

@@SimpleElectronics ok I will try and I will let you know

[@loverofthelostnarc]

Please tell the turns ratio of the torroid.

[@stevesfascinations1516]

Good job! Just a suggestion, it would have been interesting to see the oscillation waveform on your scope.

[@SimpleElectronics]

I have wound a few inductors and therefore some wave forms are not off the table!

[@Filippos_77]

can I use BC548 transistor or Lm35 transistor???

[@DiaconescuAlexandru2024]

@@Filippos_77 pretty much any NPN transistor will work for this unless it's something with a Base-Emitter tension above 0,7V-1V. So 2N2222, S9018, BC547, BC107, 2N3904, etc will work just fine for this.

[@jean-marcschmitt413]

Bonne explication, et très bon travail, Merci !

[@pleasecho2]

you were off camera at the important part - which coil ends to join to which

[@SimpleElectronics]

Just chop the winding in the middle and connect each middle piece to one of the ends, and you're done!

[@Stringandsealingwax]

"Each middle piece to one of the ends"? That doesn't seem to leave enough wires!

[@Filippos_77]

can I use BC548 transistor or Lm35 transistor???

[@tinygriffy]

Nice go on the Joule-Thief ! I like the ruler blue-tag fixture, i usually solder things like that in the already burned holes of my old breadboard :D annnd umm, ... I would like to make a humble request : Ditch the pink mat please, it hurts my eyes :see_no_evil: Pink pencil sharpener... no problem, pink power bank... go for it, pink ruler... yeah baby ! my whole (52 inch / high contrast) screen pink - yelling at me in blue and red .. I'm outa here ! Something out of wood would be nice, a warm mellow soft comforting not too too bright background tone... :D

[@SimpleElectronics]

Took it in note, but I just bought it! and my dollar store didn't have any more colors. I'll keep my eyes peeled but until I get a new one, I have to keep it!

[@Filippos_77]

can I use BC548 transistor or Lm35 transistor???

[@browaruspierogus2182]

led is in wrong place

[@SimpleElectronics]

Care to elaborate?

[@browaruspierogus2182]

@@SimpleElectronics whole idea of circuit is that mini transformer that shuts itself off and switches back on by transistor and because solenoid pushes back current like a wave it creates voltage and all is switched back on and so on. You will get the minimum voltage of the transistor drop - probably 0.6V and it is as low as it can generate from. This is not wrong as long as voltage is not going to damage diode. You may put zener there too. I put diode before emitter and not used any resistor at base. Just like normal boost converter

[@stmounts]

@@browaruspierogus2182 You don't understand it.The LED starts to conduct, so the voltage is clamped. If you omit the LED, the voltage spike may exceed the Vce rating of the transistor, but as long as the LED is connected all will be OK. BTW This is the standard Joule Thief circuit, made by thousands of hobbyists, so the LED is clearly in the RIGHT place!

[@Filippos_77]

can I use BC548 transistor or Lm35 transistor???