How many turns of wire are needed in the inductor of a Joule Thief?
By Julian
Youtuber, shed dweller, solar charge controller aficionado
Good morning all…
Youtuber, shed dweller, solar charge controller aficionado
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I love joule thiefs and am actively trying to learn to make one I want. It appears most of them are simply designed to power LED's. Are there any that have been designed to charge capacitors, if so where could I access such a design, do you know ?
Great 👍 I tried it and found out higher voltage between the collector and junction of the 10k and coil….
Best to 'scope the circuit. I would expect the oscillation frequency to increase with fewer turns. Also, the 'acid' test would be to compare the energy out witn energy in but how are we to measure the power to the LED. I might suggest a fast diode rectifier, filter capacitor and vary the resistive load. That way all measurements are at DC.
Apparently you can make a joule thief with an air core transformer and just winding the wire onto a paper cylinder. But many more turns of wire than a ferrite toroid, I would guess. Search Youtube for 1369 New And Improved Joule Thief
Great job Julian 👍🏻 I appreciate your experiment with different components but how about a 1Hz flickering LED in your next video.
Recién termine de leer todos los comentarios, gracias Julián y a todos aquellos que sumaron sus experiencias personales. 💪😉👍
Excelente aporte, un análisis extraordinario 💪
Quizás convenga reemplazar la Resistencia por un Potenciómetro…
También puedes agregar otro bobinado similar para alimentar otro LED… que funciona sobre bobina núcleo de aire, diámetro 10mm, 100mm de bobinado.
Slds desde Argentina 🇦🇷👋
I would think if the LED is strobing with no parallel capacitor. The strobing could perhaps phase lock a second joule thief using an LED as a photocell in the base circuit of the second joule thief. They could perhaps be phase locked in a master/slave arrangement. Toroids are self shielding and are therefore difficult to adjust or "tune" but transformers wound on a small plastic or paper tube could implement variable inductance which is tunable by sliding an iron slug or perhaps a threaded steel screw "core" to vary its position in the tube. A ring of such joule thieves could perhaps be quite sensitive to the presence and position of external ferrous metals because, unlike the toroids, they are not self shielding. Maybe this could be a directional metal detector. The LED pairs should probably be face to face inside black heat shrink tubing or black paper rolled around them to exclude stray light.
It just depends on what you want to do with that boosted charge. If you need light, then sending the power to an LED at sufficient brightness is a perfect solution for your needs. But as we all know, that's certainly not the only use for electricity. You may as well choose to dump every bit you can get out of your alkaline batteries into a lithium ion battery pack. In that case, you could try to do it more quickly and less efficiently, or more slowly and more efficiently. If you boost it higher to charge faster, you'll likely get fewer mAh out of the process than if you boosted it less, and used a longer charge time at that lower intensity.
One Mega ohm resistor, electrolytic cap maybe with 20 turns.
I know it's 4 years ago. But what would happen if you changed the radio between first and second coils. 4 turns primary – 20 turns secondary?
I wonder if a magnet wud have an effect on this 🤔🤔🤔
Does the core of the inductor has to be in this ring-shape or can this eventually be made by creating some turns of Cooper wire around a Iron nail?
Most of the JOULE THIEF circuits are badly deigned and the circuit diagram is incorrectly drawn. The resistor connected to the feedback winding should be connected between the positive rail and the feedback winding and the lower end of the winding connected directly to the base.
A 10n capacitor should be connected directly to the base.
This will make the circuit 300% more efficient.
WHY?
Let me explain.
Elsewhere, on other websites, I have explained how the whole circuit works but the reason for the improvement in efficiency with the 10n capacitor is due to the fact that the capacitor prevents the spikes from the feedback winding emerging from the top of the winding and all the spike is passed to the base.
This is not important for 90% of the cycle but when the transistor is getting turned on as hard as possible at the peak of its cycle, the magnetic flux in the transformer may be a maximum but its rate of increase is a minimum (INCREASING FLUX) and thus the energy produced by the feedback winding is at a minimum and the transistor is not being tuned on as hard as we want.
If a capacitor is placed at the top of the winding, the output from the feedback will only be able to come out the bottom of the winding and into the base.
This will turn ON the transistor a little bit harder and increase the EXPANDING FLUX and this will be passed back into the transformer as COLLAPSING FLUX and eventually illuminate the LED to a brighter level.
With the original "inefficient" circuit, energy is lost in the base resistor. And this is what we are using to make the circuit more efficient.
As the transistor is turned on more and more, it takes more current to do this. By adding a capacitor to the top of the feedback winding you are asking the feedback winding to deliver very little more voltage but convert the energy it is producing to create a HIGHER CURRENT. This is one of the amazing things a transformer can do but it has NEVER been discussed before.
You see. No mathematics or oscilloscopes will help you understand the efficiencies of a circuit, or how it works. You have to know how a circuit works from the FUNDAMENTALS. As soon as you see a lecturer "drag out" mathematics, you know INSTANTLY, he does not know what he is talking about. It's a "smoke screen" to befuddle you into thinking you have learnt something. But ask him to explain which component determines the speed at which the circuit oscillates (works) and you will get gobbledygook.
If you were to get one of those electronic ballasts and pulled out the 3-coil transformer that drives the transistor/MOSFET half bridge, you can use it in the joule thief too. I got mine working at 0.4V with one of those, having 2 turns on each winding. No base resistor or capacitor needed at that voltage.
very good
Photodiode can wOrk in this circuit… above LDR