Julian's Joule Thief Experiments

[@davidb4081]

Just a quick note in case someone would like to try this and not have easy access to a toroid core: Don't be discouraged if you don't have the exact components listed here; just about any reasonable setup of inductors can work just like this center tap transformer that is built in this video. I have one on a little piece of perf board that is using a pair of through hole transformers...the kind that look like regular old resistors. Despite what some results on Google would lead you to believe, just about any configuration of these basic parts will probably work out for you. Part of the fun of this circuit is modifying it to change the output and seeing just what you can and can't get away with.

[@WistrelChianti]

Having come here from Big Clive's video (chaining from atomic14's wireless charging video) I note the last thing he does is say don't let it go open circuit. The first thing Julian does is pull the LED. No punches pulled :D

[@williefleete]

Removing the LED will leave the oscillator running and may ruin the transistor if the voltage exceeds the CE voltage

[@richardssecord8511]

i would think you are correct over time at the 10v it jumped to.. maybe if you used a full 1.5v guessing the voltage would be just less than 40v just under its rating possibly damaging the it faster.. but i haven't seen any tests on this.

[@PunakiviAddikti]

The transistor oscillator doesn't stop oscillating if you remove the LED, which means that when the transistor is switched on, it will conduct between Vcc and ground freely. That's where the current is going.

[@whatevernamegoeshere3644]

Those things are marked 1-2-3 because the side ones are for power rails

[@Simon-mr6zy]

Does your diy ammeter measure (T)RMS current? If the current oscillates @25kHz you probably are measuring garbage...

[@adamwade855]

What? What are you trying to say? Sounds like you are trying to be critical of someone doing more than you...

[@userou-ig1ze]

@@adamwade855 I think he refers to the fact that the oscillating voltage is not correctly reported by most multimeters in dc mode. RMS just refers to the method of getting an approximate readout for the oscillating signal.

[@yellowcatcat3285]

Cap could function as a resonance provider in C in LCR circuit, or lower the frequency by increase capacitance of the LCR circuit.

[@californiakayaker]

your scope is dual trace right ? Take one probe and put on the base. One on the collector. compare the timing of the pulses on base to pulses at the collector with and without the led and you will see biasing of the transistor, pulsed biasing, turning on and off the transistor. second video maybe ? if you see what I think you will see, you can explain on the video.

[@BillAnt]

That's actually an interesting idea, to see the interaction of the base trigger signal vs the collector's potential. My guess is that there's a few microseconds difference around a 16khz oscillation.

[@SERGEYKACHAN-ze3rn]

*Joule thief Joule thief* kzbin.info/aero/PLh8HTLB-VWMkqsKIpgXFHg5sJDN5eGqtN

[@JerryEricsson]

Cool, I built my first working joule thief two days ago now, following Big Clive's instruction to the letter. Works great, I have a few old ones laying in boxes somewhere that I tried to build but failed so I was quite pleased to get one working. In our motor home, which we use to travel the USA and spend the winters in areas of the states that are without snow, thus the nickname for folks such as ourselves "snow birds" we use tons of AA batteries, in nightlights, my metal detector, and even my label maker. So I always have lots of the blasted things laying around, and my main tool is a battery tester. So now I have a home built light that uses the old batteries instead of tossing them. I plan on building a small holder for my thief so it can be used as a light beside my easy chair in the rig, just to take the dark off when I actually put a tiny slide switch on mine, and used big Clive's method of casing with hot glue.

[@jimmybrad156]

I guess a lot of your things could use Eneloop NiMH's instead of primary (single use) AA's?

[@LemoUtan]

What's the actual inductance on those things? Does your little component tester tell?

[@johnm2012]

A few tens of microhenries per winding. I'm getting in the region of 20 to 40 uH in my experiments. The capacitor really makes a difference. It allows you to increase the resistor to 10k or more but it works best if you move the resistor from between the coil and the transistor base to between the positive supply and the secondary coil. Then put the capacitor between the junction of the resistor and coil and the negative supply. The best value seems to be somewhere between 1nF and 10nF. For such a simple circuit there's much to experiment with. The windings don't need to be symmetrical. You can use fewer turns of finer wire for the secondary (base) coil, which will allow room for more turns or thicker wire for the primary (collector) coil. You don't need such a large ring to wind the coils on. A tiny ferrite bead with 8 or 10 turns will also work. You can also experiment with the transistor as they have different voltage drops when fully turned on Vce(sat). The BC337 seems to be a particularly good choice. It's a fascinating circuit because, while almost anything will work there a huge scope for refining it and squeezing every last joule of energy out of that "dead" cell. More esoteric variations include using a germanium transistor because it will continue to oscillate when the cell voltage drops lower than 0.7 volt and substituting a MOSFET to reduce the bias current to almost zero - though in that case the gate bias voltage is a problem, requiring additional circuitry or a couple of button cells to provide it.

[@jack002tuber]

I wish you'd of put the scope back on when you added the caps. Great vid. I hope we all learned about inductors

[@craiginboro679]

can you put 1 channel of your scope on the bottom of inductor 1 and likewise with inductor 2. test 2 can you simultaneously check current through Led and b.e current on transistor and then remove led. I have a suspicion transistor gets hotter when led is not in circuit

[@BillAnt]

At 25:18 he's mentioned Colin Mitchell having been able to cut the power usage to about a third, which may be possible with a precise selection of resistor/capacitor values, including a high efficiency inductor, and most importantly a very efficient LED (expensive one). Also, putting a "snubber" cap across the LED to smooth out longer duty cycles of the oscillator may help too. This tiny circuit has been around since 1999 (and possible even before that in some other variation), with its remarkable simplicity and efficiency has spawned countless videos. It's a really nice little project for even beginners to try, well if it wasn't for having to make the coil by hand. :D

[@tonylorentzen]

Put an oscilloscope on that transistor. I think you'll find that when you jump the resistor with a capacitor, the "resonance" (for lack of a better word) of the transistor drops. That's probably why you see a drop in power draw.

[@JUANKERR2000]

27:00 A 300 % reduction doesn't mean a reduction to 1/3 of the original current, that would be only a 66 2/3 % reduction. A 300 % reduction is impossible as reducing by 100 % would result in zero current! :-))

[@SatyajitRoy2048]

LOL

[@ElmerFuddGun]

Maybe the "300% reduction" means it is producing more than it is using... it is a free energy device! ;-P I see people making these simple "reduction", "saving", "bonus" calculations wrong all the time. People that should know better in the sciences or consumer media. They don't seem to understand that if something cost 50% less than the other doesn't mean the other cost 50% more.

[@reggiebacci]

This is what happens when you learn maths from the batteriser datasheet. :P

[@Simon-mr6zy]

Silver Legend on Talking Electronics it says improvement of 300%. See www.talkingelectronics.com/projects/LEDTorchCircuits/images/LEDTorchCctB.gif

[@JUANKERR2000]

That's as illogical - an improvement of 100% would be a reduction to zero!

[@terraforming782]

Using a fixed value resistor is pointless use a potentiometer and fine tune it untill the led at its brightest use a small value cap across the resistor after fine tuning you will find two sweet spots where brightness is maximum remove the pot measure the ohms select a resistor closest to the meter reading connect the cap. Across the resistor and you have max brightness for min current

[@petermuller6923]

Yes, that is really important. I did that and the LED is much brighter and the circuit is more efficient.

[@BillAnt]

Not a bad idea, with a pot one could easily find the "sweet spot" of brightness and consumption which is a functions of the charge/discharge duty cycle. However we can't violate the laws of energy conservation no matter how hard we try it, we can only make it a bit more efficient. At 25:18 he's mentioned Colin Mitchell having been able to cut the power usage to about a third, which may be possible with a precise selection of resistor/capacitor values, including a high efficiency inductor, and most importantly a very efficient LED (expensive one). Also, putting a "snubber" cap across the LED to smooth out longer duty cycles of the oscillator may help too.

[@SatyajitRoy2048]

For this video my comments would be...1. You have multi channel scope and it would have been nice to see both sides of the inductor voltages at once. A serious problem when someone is not familiar with what a scope can do. 2nd point is, you need different turns ratio for two coils in order to optimize the overall current consumption. 3rd point is, your MPPT charging wont work at its best if you use that green coloured inductor. Thats a pure ferrite core and you need something with lesser permeability. This green ferrite is okay for making high value inductors but not suitable for buck/boost converters.

[@cmj20002]

Have you ever checked the frequency that they are oscillating at? Mine was 170 KHZ, but the other one I built is 142 KHZ so there is a difference in the windings in each inductor and I figure that is why my two joule thief's have a different frequency.

[@AnsyCrofts]

Wondered when our "Jules" was gonna become a jewel thief.... Seriously, I was working on an MPPT-type thingy for an environmental company in Finland. Reason? They had data loggers in the wilderness, powered by 9Ah SLA batteries. Their method was to stick a 10-watt panel in series with a silicon(?) diode (Schottly?? Never heard of her, mate!) and either NO charge in winter, or just boil the hell out of the batteries in 24-hour daylight in Summer... Which is why your Arduino Muppet project was of interest... BUT, Winter...I can still get a few volts out of the panel, and use it to charge a BFC (Big..er...Friendly...Capacitor), then dump it into a Joules Thief, give the battery a bit of a kick...Then, when Summer kicked in, turn the whole mularkey to a MuPPeT device. Sadly, my work-experience ended, and the company couldn't even afford the necessary insurance for me (as unemployed) to work for free. RATS!

[@JulianIlett]

Cool story - thanks. I am thinking of putting the joule thief on a supercapacitor.

[@AnsyCrofts]

...Actually, once the "BFC" had got enough charge, I'd use a Unijunction Transistor* to trigger a FET switch to dump the BFC's charge into the 'theif - then to the battery. *UJT - (2N4656) - That'll get your younger readers scrabbling in Google! Us old-timers (pun intended) know what they are!

[@ZeedijkMike]

+Andy Crofts UJTs. Haven't seen them around/used for quite some years. Useful little device. I wander what have taken the role now a days?

[@jimsmindonline]

A very mysterious circuit, love it's simplicity but complex operation! Took me ages to figure it out when I first came across it and it's hard to explain​. I've seen the notation for this style of inductor drawn as a transformer but with dots marked next to the coils to indicate one winding is opposite. Then in this case the top 2 connections are commoned to positive. You're almost there, i find breaking time down slow motion like you did helps a lot. Remember that the field produced by the first coil induces current in the opposite direction in the second coil and vice versa. I wonder how measuring the voltage at collector to ground effects the operation, I'm guessing that the load of even a meter must effect things?

[@RicardoPenders]

First of all, I wish you a happy new year. I made a few joule thief circuits myself and used iron powder cores instead because after testing I found out that the iron powder cores are better because you're using the core to store energy in a magnetic field, because of the iron powder core the magnetic field is harder to flip around and that helps with efficiency and I also don't hear any ringing in the core as you normally get when you use a ferrite core. I used the joule thief for two different reasons, the first was just to see how it works and if I could get it to light up some LEDs of an empty battery and I wanted to know how long the LED could run continuously of the dead battery, quickly I discovered that my transistors are getting way to hot when I use a 1k ohm resistor as you suggested in your video... So I replaced the resistor with a 10k ohm one and even that was not a high enough value resistor, then I used a 100k ohm one and after that a 1M ohm one and my LEDs are just as bright with the 1M ohm resistor as with all the lower values but now I don't have the thermal issues anymore. However I do have a second way that I'm using the joule thief circuit to get a string of 20 white LEDs to light up as bright as possible and I'm not using a battery power source but an old 800mA @ 5 Volt Nokia charger, that's for my helping hands with magnifying glass that I customized by adding 22 white LEDs to make my workspace much better... Again I used the iron powder core but now I wanted to see what happens if I made the windings different by adding one more winding on the collectors side so I still have the center tap with one winding going round once in one direction to the resistor and the base of the transistor and two times in the other direction making it a 2:1 coil instead of the regular 1:1 coil and I also added an extra parallel connected transistor, a diode and capacitor which is connected to the 20 LEDs string... It's not the most efficient circuit and it gets pretty warm to the touch but the 20 LEDs are lighting up very bright which is exactly what I wanted for that application, it will run on a 3.7 volt Li-Ion battery but not very long... it's completely drained in a couple hours which is an unexpected result, I thought it should keep running for days but it doesn't if you're pushing the LEDs to the limit. All in all I find the Joule Thief a lot of fun to play with and it's probably the most forgiving circuit of all, I did manage to burn a few LEDs and transistors but that was totally my own fault because of fault wiring or driving the components way out of spec just to see what happens... LOL 😆😆😆😆💥🆒

[@GhostsOfSparta]

23:47 Your transistor on time is high, so more energy is getting wasted. Change base resistor values to increase or decrease frequency. Or give less turns on base side of the coil.

[@station240]

I suspect the voltage is being clipped to 10V due to the ferite core being saturated, not any form of leakage/breakdown of the NPN junction in the transistor.

[@stevejones8665]

Hi Jullian wonder what frequency the cct is oscillating at...the wonderfull strange world of RF comes to mind would also be interesting to see just the led current. ..adding the capacitor obviously changes the frequency of oscillation and as a ham i used to play around with RF to light Fluorescent tubes. ..time for another video i think....Cheers Steve Liverpool

[@pleasecho2]

Where did you get the ammeter?

[@brianclimbs1509]

Could the maximum voltage at 24:20 be affected my the input capacitance of the scope? I would be curious to see if putting some additional capacitance to ground in parallel to the scope would lower the voltage further.

[@jlucasound]

That is awesome how you built the inductor onto that breadboard friendly header!! Nice!

[@jaa93997]

Julian: its fun to build coils (chukles) Me: remembers masters degree school, design and calculation of impedance matched coils at microwave frequencies (cries)(a lot)(in pain)

[@BillAnt]

Yep at microwave frequencies even a round trace vs a square trace on a printed circuit board can have a noticeable effects on signal attenuation, leaks etc. ahhh the fun of microwaves. :D

[@Raggar_]

@@BillAnt All of us who love the electronics we are masochists XD

[@PeteVanDemark]

What happens to brightness and current consumption when a fresh new battery is used?

[@georgestewart5879]

really good video Julian, understand a lot more about the joule thief now, thanks.

[@arthurschroeder3003]

I made plenty of these on my cement battery experiments. I found that if you put a electrolitic capacitor between the + and - of the cell the led will flash. This happens when the battery is almost expired. keep up the great videos.

[@chrisleech1565]

Love the header pin mount for the ferrite Lego style micro boards...who knew?

[@Matlus]

While you have one channel of your scope connected to the collector, try connecting the other channel of your scope to the base of the transistor. That may help explain things while you have the LED out of circuit.

[@larryyounger8674]

watching the last few videos, any bets on when Julian will sharpen that pencil?

[@BillAnt]

Yes yes, that's always and exciting thing to watch for. :D

[@magnets1000]

Those CFL bulbs seem to last much longer if they are mounted facing upwards rather than downwards from the ceiling, it must be the heat

[@corkymork]

How about seeing how many series LEDs it can drive. And at what current consumption.

[@lemonlees]

bigclivedotcom runs a series of about 20 on his video.

[@jayherde0]

Might need to change the number of windings to get the voltage high enough.

[@ExStaticBass]

Having watched this I had a bit of a play session myself. I'm using 1400mah NiMh cells as a point of curiosity to see just how long they'll run before needing to be recharged. The end goal is to see if I can make my own solar light of sorts. This video helped a lot in that respect as I wouldn't have thought to put a capacitor there. Thanks for sharing this...

[@kardeef33317]

Thanks for the video Julian, with this video I am finally starting to wrap my brain around this.

[@OrthoRocks]

@Julian. A very noob question regarding joule thief...is ferrite toroid ring is necessary or any iron piece like nail or screw can be used to make the inductor. Also will there be any change in efficiency?? If possible please make a video on this too.

[@BritishBeachcomber]

From memory, adding a capacitor raises the turn-on voltage. So it won't work on very low battery voltages unless you only add the capacitor after the battery is connected.

[@555-xd1fo]

The smallest breadboard

[@pyotrleflegin7255]

Very good! One of the best JT posts I've ever seen -- I really like the way you wound the inductor!

[@boblewis5558]

+ Pyotr Leflegin It's called a bifilar winding and is as old as the hills - a standard, relatively easy way of winding two coils of the same number of turns on a core. Also the "start" of any coil is normally marked on a schematic with a dot to indicate the "polarity" of the coil so that the induced voltage polarity (direction) can be established easily. In this case, in Julian's schematic the left hand coil would have a dot at the top (common connection point) and the second (right-hand coil) would have the dot at the bottom. This is why the end connections have to be cross connected for the common point and explains why, without doing that, the coil will not work as expected since the induced voltage (from the collapsing field) will be in the wrong direction. The circuit is basically an oscillator and in order to oscillate requires positive feedback. Connecting the coil the way Julian first had it produces negative feedback thereby effectively (and actually) preventing oscillation, i.e. why it wouldn't work at first.

[@pyotrleflegin7255]

Thank you for your very clear explanation. I used to be an electrician but this kind of thing wasn't really in my job. Again, thanks for the advice ;) !

[@petermuller6923]

I built a LED dog collar with a Joule Thief to power 4 LEDs. I used two inductors (they look like dark brown resistors and also have the colored rings) instead of a coil to fit it all into a thin transparent flexible tube. It works perfectly for 60 - 100 hours with a single AA battery, even under water. It runs the battery down to about 0,6 Volts until the LEDs get too dark. I love it. It is better than all LED dog collars, i ever bought and cost me about USD 2 for parts and 1 hour of my time :)

[@JulianIlett]

You are a true maker :)

[@petermuller6923]

Thank you :) I tend to overengineer everything i make and really enjoyed this one evening non-AVR project in contrast to the complex machines i usually build.

[@xanataph]

Well you have saved me a lot of trouble should I ever decide to make a JT! :) Maybe an exercise in greater efficiency (& further understanding of inductors) would to be to experiment with different tapping points? i.e. an asymmetrical amount of turns.

[@JulianIlett]

Yeah, I want to do more extensive joule thief experiments soon

[@Tech-Relief]

I am wondering if the scope's 1M ohm input impedance loads the circuit down enough so that you only saw 10 volts?

[@RovanRCTube]

Any ideas on building a large version of this. Say to hook to a 12v car battery depleted to 1v and power a 12v bulb.

[@Kai-Made]

I was able to effectively double the current lol...by not using the resistor correctly. This allowed for a much brighter light but for a much shorter period of time. I like this circuit for playing with because it is nearly indestructible and easily tweakable.

[@etro8564]

where do you get that putty ? that you place the electronics on

[@Shit_I_Missed.]

the trade name is Blu Tack, or Blu-Tack. it's a wonderful material, you should definitely try to find some. Any store with an arts and crafts or office supplies section should have it

[@etro8564]

thanks for helping me !

[@justbearwithit1642]

What if you put a capacitor instead of an led?

[@himselfe]

Isn't it simply the case that with the transistor on, it provides a lower resistance path to ground, so current stops flowing through the resistor turning the transistor off again, and that's how it oscillates?

[@abcdefgh1279]

The C-E voltage rises only to about 10v. At this point, the voltage induced at the second coil (left side) is enough to trigger the transistor ON. I think the led would burn out instantly, if you'd put it back in at 40v.

[@NicholasAarons]

Fantastic Video Julian. Keep up the great work. Nick.

[@bens4446]

What a weird circuit! On mine the LED is oscillating on for a few seconds and then off for a few minutes. I'm guessing it's because not enough windings around my paper tube core. Ran out of wire.

[@d3spis3m3]

So how much does the mA drop when you remove the LED with the capacitor with the resistor?

[@CountryGeek-hr8tk]

The CFL bulbs don't last here in the USA either where we have 120volts.

[@grizzbeeuno2242]

Hello, Great Video as always .... Can you please tell me the name of the "play dough" you use for holding your parts and where do you get it ?

[@JulianIlett]

+Grizzbee Uno Thanks. It's blu tack, made by bostick.

[@grizzbeeuno2242]

Julian Ilett Thanks

[@kuhrd]

Basically, any poster putty generally seems to work. I have used the white and the blue from several brands and they seem to work well.

[@stevejones8665]

Grizzbee Uno It looks like a product called Blue Tac it is used for putting posters and pictures onto walls in a room so you don't damage the paintwork on the walls...It comes in different colours depending on what make it is...you can usually find it in most stationary shops and some household item shops. ...it's not play dough as such ...hope this helps. .

[@WistrelChianti]

Brill! I was hoping to see a scope in the mix with this one and didn't come away disappointed : )

[@renxula]

Good stuff, but I would've liked to see both the base and LED voltages on the scope, at the same time to better see what's going. And the frequency it's running at, etc. If you do make another video about this, I hope you'll scope it more!

[@JulianIlett]

I will :)

[@donnybowers7832]

I love your videos Julian. I've watched quite a few of them. I made a joule thief yesterday using a 2n3055-D transistor. The toroid came out of something I scrapped and looks to have a lot of windings (phone wire). I'm testing it out as a sort of 5w solar charge pump for a lead alum battery I made a couple years ago. I've only had it hooked up 1 day. So far so good, but I'm wondering if the joule thief will push the whole 300ma that the 5w panel is good for. If anyone knows if I'll be losing amperage with this circuit, I'd appreciate any feedback on the idea. So far it looks like it's almost acting something like mppt. It's definitely charging and I just have the panel in a window inside the house. It's below zero here in Michigan, so I don't feel like mounting the little panel outside the house yet.

[@richardssecord8511]

Did you do any videos on your project was thinking of something like it made me wonder how it went..

[@n3qxc]

You stated that you would be revisiting this project... may I ask that you show us more with the scope... it would have been interesting to see the signals going to the base of the transistor with and without the capacitor. And what if you changed the winding ratios on the feedback portion of the circuit vs the tank coil.... what about a cap across the tank circuit... and its effects.... I find this to be a very interesting circuit, and yet so basic... thank you for making this video.

[@bridgendesar]

what if you used a hall effect device to detect the magnetic field, instead of the center tap?

[@kirkb4989]

What is the max voltage you can put into this and drive an LED. What would happen if you put 3v in and let it drain down to minimum?? I'd love to be able to use a full CR2032 then run an LED and use it to run the LED when the battery drops down. I know nothing is free- will it consume more power when the battery is full voltage? How much less efficient would it be??!?!

[@rodjara8506]

Really enjoy your videos and learn all the while. Thank You

[@daveb5041]

So it works by just pulsing the LED really fast at a usable voltage so it looks constant to your eye?

[@terryhayward7905]

This is a useful demonstration of back EMF from an inductor.

[@AlojzJakob]

You can try changing the code in your ammeter, so it averages out the reading

[@BritishBeachcomber]

The collector winding provides negative feedback, just like in a Blocking Oscillator, to turn off the transistor. Then the whole thing repeats.

[@sardaclan1]

loved the video. really helped me understand inductors as well. look forward to seeing more..

[@2wiseib]

Suggest that you wind only one length of wire and after ten turns or so make a loop and then keep winding in the same direction and that will make your center tap without the mucking around. So much easier

[@realflow100]

About 10-12v it WILL CONDUCT MUCH SOONER THAN 40V in reverse Because the LED is reverse biased and the inductor is inducing the voltage forwards into the LED and BACKWARDS into the transistor. Therefore with no LED. The transistor emitter-collector is getting a reverse voltage from normal and conducting at about 9 to 12v Thats a relaxation oscillator with a single dead AA battery Full explanation given here you go! Datasheet 2n3904 maximum collector emitter FORWARD voltage 40v when breakdown occurs reverse maximum is 10v when breakdown occurs

[@kg2nc]

Reminds me when I use to make 4to1 balms to use on twin line for amateur radio antennas. Can you imagine if you had to make a bunch of them for a project. Would it still work if you had a few turn twisted while you made the turns.

[@gautamdamodaran]

Does this have to do anything with the negative resistance region of transistor operation?

[@joruss]

If you're persistent enough you can fit a joule thief into regular tungsten light bulb case (without resorting for smd parts!) and make any old torch a LED torch that runs even on flat batteries. Good fun. By adjusting this resistor you can maximize light output and tune the circuit to the inductor you've made. Another neat trick is to use it for super emergency lighting because this little jewel (pun intended) can easily power 5m led strip out of dead batteries.

[@kjyhh]

Such high votiage the current might be pushes back to the battery?

[@ZeedijkMike]

I'm running a small pice of 12V LED strip. (2 × 3 LEDs) from a single AA cell. This simple circuit just keeps on giving.

[@ZeedijkMike]

I have measured up to 50V across the CE junction (with no LED connected) on my scope.

[@matteopascoli]

Hi Julian, how do you know how many spires to make, given the Ø of torus and of wire? Or it doesn't matter?

[@ucmetoo1]

concerning the 10v break down come to mind. 1. you are reaching the dv/dt induced break down. 2. the transistor breakdown voltage was reduced due to previous breakdowns when you removed the led before

[@thextremeking]

2) Transistor BREAK DOWN voltage hmmm yes to words seem to suggest just that ;)

[@ucmetoo1]

thextremeking Thank you for your kind remark and correction.

[@kensmith5694]

I doubt he is running into dV/dT problems with a 2N3904. I know they live while doing: dV/dT = 5V * 2 * pi * 100MHz = 6V/nS

[@ucmetoo1]

Ken Smith hmm... this starts to be interesting. the voltage to consider is about 10v. I think i am going to do some experiments.

[@kensmith5694]

The cores in question are most likely crappy at the speeds you want to play with to push a 2N3904 to near its limits They are good to above 200MHz with moderate collector currents. The common sorts of cores stop looking like cores well before that. In the distant past, I made an air core step up circuit. It was basically an Armstrong oscillator with a schottky rectifier. I'm sure none of my neighbors could watch TV until I moved it inside a box.

[@1981dasimpson]

i found with a cap in the tanking arrangment acrossd the resister and a cap across the led legs i found the current dropped but also the led seemed brighter

[@JulianIlett]

+David Simpson cap across the led, good idea, I didn't think of that.

[@1981dasimpson]

another idea been tried was not having the led in the circuit at all but haveing another winding indipendent of the others and using that to power an led and so on i tried many idea after some time i had to stop as my hands world hurt with all the winding of them

[@ibrahimkayani2824]

could anyone plz help me I see a lot of ads online of 2in1 solder stations but don't know which one is the most reliable for my budget plz if u have any experience in this your knowledge will greatly help me

[@realflow100]

I have a 3-LED flashlight that runs on two AA's which can light the LED at full brightness down to 1v no problem I use two rechargeables It uses a very similar joule thief circuit. except the inductor only has TWO LEADS. And the transistor shaped object gets warm. the inductor gets warm And about 400mA is drawn from the batteries when fully charged. When they're dead its still pulling enough to make the three LED's pretty bright (straw hat LED's very wide light angle. but theyre in a flashlight reflector so its more of a smooth beam)

[@byroboy]

Julian, have you tried to run a series of LEDs? It would be interesting to see it light 2 LEDs, etc. and see how the current changed.

[@jlucasound]

Big Clive used a string of LED's and it seemed to work fine. I am not sure if they were parallel or series. I would think parallel.

[@jimmydemetriou7847]

Hi Julian, thanks for the video. I was wondering on the waste aspect of batteries when used in devices. It seems almost as though this might be able to be used to get more of the stored energy in the batteries to keep a device, such as a battery radio, going longer until the batteries drain more completely. Would this possibly work? If so there is a possibilty of adding this small amount of circuitry, with or without the LED, into the battery powered device in the battery circuitry without damaging the device and saving on wasted energy and making it truly useful other than shining an LED just to drain the batteries? Seems like a worthwhile consideration. I'm not trained in electronics, so forgive my ignorance if there''s an obvious reason why this type of circuit couldn't be used as I suggest.

[@arifanwari3168]

lol that little ferrite ring's like a little pearl popping out of a clam.

[@DonaldSleightholme]

i built a solar powered one from a garden light with a green led and it lights on 0.58 volts and 0.20 current on the 2m multimeter setting? i was using the flashlight on my iPhone to power it. 🤔🤷‍♂️ will this damage my transistor. i don’t have a oscilloscope 😐😔

[@gameoverwehaveeverypixelco1258]

could this be used to make appliances more efficient, run on less power. redesign the internal components to be more efficient.

[@sparkyprojects]

When you remove the led, the circuit is still oscillating, with the led in you are measuring the led and transistor current alternately, if you change the base coil to a switch, you can turn it on to see the transistor/coil current, turn it off to see any led/coil current, do this with the scope attached.

[@WaltonPete]

Excellent video! Informative and interesting PLUS great idea where to get hold of small ferrite rings for free. I was very happy to see you get the scope out as it gives an excellent insight into the working circuit. Keep up the great work!

[@tartrazine]

28:54 Solar Charge Controller PRODUCT?

[@JulianIlett]

+Tartrazine Slip of the tongue, I meant project of course!

[@ancapftw9113]

I wonder how this would work if you tried to charge a supercapacitor off of it instead of an LED? You'd probably need to add something to limit the capacitor to lower voltages if you wanted to run something at 5v, though. I'll see if I can figure out how to use a 5.1 v Zenner diode to pass the proper voltage without going over voltage.

[@harryjnr2335]

when cfl first came out they lasted for ever

[@richardboyce4921]

Excellent video Julian, very informative and an understandable breakdown of how it works. Keep up the great work. Missed your calling as a teacher.. lol

[@Dippo6905]

Nice, time to open lamps and get out the ferriet. Good hint!

[@FadiFadi00]

Dippo6905 I always do that 😂

[@johncherry108]

What a coincidence : I saw something on the interweb yesterday which suggested that 'ferriets' make good pets. Well, I think it was 'ferriets'

[@Dippo6905]

Ferret is a pet. Ferret also like electronics, they tear everything apart. Really.

[@Dippo6905]

I had a few lamps but they don't have any electronics inside. Are PSU and TV's and radio's the other best option to find ferriet? I also found out that there is a color scheme, green ones are bad, yellow is good, white is best, blue is good. Black is probably iron.

[@AnsyCrofts]

Good idea! I muse rummage around in my junk box and see if I can ferret out a ferrite...:)

[@lawrencel3188]

You mentioned the development of a 'reverse voltage' when the transistor turns off, but the scope shows no neg voltage being developed. So is your head indeed straight on this specific inductor useage, or maybe not quite yet?

[@jayherde0]

The reverse voltage would be in one of the coil windings as the field collapses.

[@JasonMasters]

The reverse voltage is what the scope is measuring. When current is flowing through the transistor, both probes of the scope are effectively connected together so they measure nothing. The probes only have a potential difference across them when the transistor is not conducting, which is when the "reverse voltage" is developed from the transformer. In simple terms, a coil of wire tries to resist any change in current flow. How much it resists is its "inductance." When the transistor switches off, the transformer winding tries to "re-establish" the current flow and it does this so violently that it produces a voltage higher than that which was across the winding before the current was switched off. The LED both uses the high voltage to light up, and also "clamps" the voltage down to the LEDs forward operation voltage. In this configuration, a circuit like this really can't be used for anything but lighting a LED, but the basis of this type of circuit is what makes a DC-to-DC step-up converter circuit (boost circuit) work.

[@jayherde0]

Not quite. The collector voltage to ground IS the voltage across the LED. Yes, it's effectively 0 when the transistor if ON and the LED will be off. But when the transistor is OFF, the LED clamps the voltage to the forward voltage of the LED. That voltage/current/energy comes from the energy that is 'stored' in the magnetic field of the coil. which is released as the field collapses. I don't know if Julian is going to go that far into 'Field Dynamics'. It seems that Clive did good when he coined the name "Joule Thief". Good on you BigClive :-D

[@jmjpowerjoule]

I figured-out how to hook-up a PNP transistor for the joule thief circuit. I'll explain it to anyone that asks.

[@travismoore7849]

Try putting a piezo disc as a resonator or across coil to keep constant voltage.

[@wbfranks]

Jullian, in your search for the reason your flyback voltage without the LED limits at a value lower than you expected, check the Vebo spec limit and recall you have a coupled inductor...........

[@jlucas97701]

Just curious, at what frequency was it switching the transitor? I could not read that on your oscilloscope.

[@JulianIlett]

About 25kHz I think

[@blg53]

Julian, could it simply be that you can't really trust your ammeter. The shape of the current is neither DC nor harmonic AC, not sure how your device can make a meaningful reading out of it. What might be happening is that when you remove the LED the shape of the current changes and even though the actual consumption drops the ammeter does not see that. You can prove it one way or the other if you put a small resistor in series with the battery and use your scope to assess voltage shape across that resistor. And with a reasonably simple calculation you can estimate the effective current draw with and without the LED.

[@FredBedderhead]

Julian, the coil is acting as a load and the current is so low is because of the pulse width modulation

[@peterdkay]

Try varying resistor value to improve efficiency.

[@MusicalBox]

Based on what I understand from Julian's description, the resistor is there to limit the current used to turn ON the transistor. How would it improve efficiency if you change the resistor's value ? BTW, I'm not trying to troll your comment, I'm just curious.

[@peterdkay]

By increasing resistor value you reduce quiescent base AND collector current. Reducing quiescent current will improve efficiency. However if you reduce it too far LED brightness will decrease.

[@MusicalBox]

Thank you

[@donnybowers7832]

I just made a joule thief this evening and I thought I'd try a 1k pot to see what it does. The funny thing is, it didn't do anything. The LED is getting the same voltage (3.7v) at 1k as it gets at 0 ohms. I'm an amateur, so I didn't realize that the resistor is there to limit current at the base. But, funny thing is, I tried a 10k pot and it didn't change anything either. Maybe it's because the battery I'm using was holding about 1.1 volts when I started it up. It will be interesting to see what happens when the battery voltage goes down a bit. I have one joule thief somewhere that I made a year ago and forgot to put the resistor in. I thought it was odd that it still worked. I imagine it would shorten the life of the transistor.