Big Joule Theif

[Watson]

Thanks for the explanations. It is fascinating. I will study your circuit more closely when I got some time.

For those who are interested, I'd like to give an explanation of JT here:

Let's start with the point of time where there is ZERO collector-emitter current in the 2n3055. Now because of the battery, there will be base-emitter current through the trigger coil, limited by the resister in series. This makes the transistor close (as a switch) between collector and emitter, but keep in mind that there is a ceiling cap on the current that can flow through (roughly equals the base-emitter current multiplied by the beta parameter of the transistor). So current in the power coil starts to increase, until the current ceiling cap is reached, at which point the current stops increasing. Mind you one more crucial detail: while the current was increasing in the power coil, the trigger coil can pick up a little boost and that help contribute to the base-emitter current. Now when the current in the power coil stops increasing, such a boost ceases to exist and this immediately drops the ceiling cap quite a bit (say, 20%, depending on how much boost the trigger coil picks up from the power coil). Such a drop of ceiling cap sends the power coil into its down turn at once -- the current in it starts to decrease, and such a current decrease in the power coil further lower the cap through the pick up (inductance) at the trigger coil ( in fact, the decrease is usually fast enough to shut off the transistor completely). The decrease stops until the current in the power coil reaches ZERO, and we are about to start a new cycle. That's it, folks!

In the above he talks about the current being limited by the transistor's beta (hFE in the datasheet). The beta or current gain is curcial to getting enough current through the transistor to power the output (LED in a JT). Conventional transistors including the 2N3055 don't have good beta holdup at low collector voltages, the beta drops off when the collector voltage is low. We need a special transistor that has very high beta at very low collector voltages. And it also needs to have very low saturation voltage at very high current.

If you look at the transistor on the flash unit from a disposable camera, you might think, how could that tiny transistor be drawing over an amp from the AA cell when it's charging? but it can and does! In fact that transistor can handle up to 5 amps!! That's 10 to 50 times the current of a conventional 2N3904 or 2N4401 (same as the PN2222).

So what are t hese super beta, low Vce(sat) transistors? Some commonly found ones are the 2SD965 AKA FJN965 from Fairchild, or the KSD5041 also from Fairchild, available from Mouser.com for $6.60 per hundred, which is 16 times cheaper than the 2N3055, at a buck each. You could burn out a dozen of these and it'd still be cheaper than burning out a single 2N3055. And the good part is that a single KSD5041 will crank out more power than a 2N3055 in a conventional 1.5V Joule Thief circuit.

You don't believe it? Try it sometime, and you'll be a believer. You could put a dozen of these in parallel and drive a high current JT to light up a 1W or 3W Luxeon Star. I've put 5 of them in parallel to drive a Luxeon 1W to over a hundred mA. But my problem is that the 1.5V power supply maxes out at 1A, so I gotta beef up my PS. Maybe I should try a couple D cells in parallel? Whatever..

[Watson]

UPDATE - LEDs Have Air Bubbles In Lens

Wish it ends well -- keep us updated about the ebay story.

After a week or so Paypal made a decision in my favor, so I logged on to PP and found $30 credited to my account.

I found this Chinese Co. that sells cheap LEDs for throwies, but you have ro buy a lot of them. Click on fhe x-type box. Most other types, too.

Power LEDs

[Watson]

Pulse Inverted Joule Thief Circuit Schematic

Hi guys i did a updated drawing of Slayer007 drawing
of the Pulse Inverted Joule Thief Circuit

One thing that is very important is the 0.1 uF bypass capacitor across the power supply pins of the 555. Leaving this out can cause weird and unpredictable 555 operation, like spikes in the output. Read the 555 datasheet to find out why. Also the overall circuit should have a good size bypass capacitor at the power supply input pins. A good starting value is 1000 uF for each amp current. Like 470 uF for 1/2A, or 220 uF for 1/4A, but more doesn't hurt. Again,this is necessary for good stability.

The.0047 at winding B2 seems a bit too small, too.

[shubhamforme]

@Xenomorph

Well first of all the charging part can be HV (not as High as the Neon side). With my 90 turn coil I got 500V voltage spikes. I have not scoped this coil yet but its definitely enough to light a neon so we know its more than 90V.

My idea is to have a relay switching between:
1. lighting the Big Fluoro off the secondary coil
2. charging a cap off the Collector

We do this fast enough so that we do not notice the pulses in the light. Its hard to charge a light the Fluoro at the same time so why dont we do one when the other is off.

It removes the 555 from the front and puts it to the back. The JT will have full on time but im sure we could get better charging out of it.

Check out the attachment, I drew up a circuit. I was just about to try it today... I had the 555 built, got the relay switching, then it died on me!! Damn!
-shlodo

hi there!!
i liked this idea of yours ,, even i ws trying to come up with something like this....but was unsuccessful...maybe you can try that..??
can you past a circuit of this design?
thx

[slayer007]

Is there a simple way to wind large TOROIDS where you have
100+ winds on them.

David

Yes David

Wind your wire on a long thin bolt.
Wind two strands on the bolt for the JT part.

Then feed it throught your toriod(kinda like sowing).
Then do the same for the pickup coil but only one strand of wire on the bolt for the pickup coil.

[David_Cooksey]

Winding Big Toroids

Is there a simple way to wind large TOROIDS where you have
100+ winds on them.

David

[rave154]

thanks

Thanks for the replies guys,

a bit of a an electronics newbie here, so all help appreciated,

i was just drawn to wanting to recreate slayers high voltage theif circuit when i saw his voltage go over 1000 in the vid, am a bit of a voltage hound as well as a newb ( dont worry, i take ALL precautions ! ).

[David_Cooksey]

Updated Drawing

Hi guys i did a updated drawing of Slayer007 drawing
of the Pulse Inverted Joule Thief Circuit

[slayer007]

hi Slayer & all,


Slayer, could you be so kind as to repost a slightly clearer circuit diagram of the type you attached in post #1 of this thread as i am a little confused by the connections regarding A+ , A-, B+ B-....

Thanks a bunch

David D

Hello Rave154

There is also a differant circuit on page 4 post 117.

That one uses two transistors.

The dots show the start of the coils.

NOTICE that positive A goes with negative B

Edit:
When I say positive that is just the start of the coil winding.
And negitive is the end of the coils.
So positive is the start of the coil and negative is the end of the coil.

[rave154]

calling Slayer007

hi Slayer & all,


Slayer, could you be so kind as to repost a slightly clearer circuit diagram of the type you attached in post #1 of this thread as i am a little confused by the connections regarding A+ , A-, B+ B-....

Thanks a bunch

David D

[lanenal]

ebay story

Wish it ends well -- keep us updated about the ebay story.

And it can give you a shock if you touch both coil leads and there is no load on the coil.

I requested a return and refund, but the irascible seller refused and threatened that if I gave negative feedback and made a dispute with Paypal, they would have me banned from buying LEDs from all other ebay sellers.

I left negative feedback, and filed a claim and dispute with Paypal, and I am still waiting for the decision from Paypal. I'm very disappointed that it ended this way, but sellers have to know that LEDs with air bubbles in the lens should be rejected at the factory and should never be sold as new, top grade parts. Sellers should be selling these as 'seconds' or factory rejects.

Yeah, can you believe that? Banned! I've made only 50 transactions on ebay in more than 4 years, so is being banned going to make my life any more difficult? No. But these LEDs with flaws are being sold as top grade parts and that has to stop.

[Inquorate]

constant

@ Watson - tried using a zener diode?

[Watson]

How to Convert Super Cap to JT?

Oops, forgot the pic.

Here's what I (finally) got from Mouser, after waiting for over a month. I now have several 50 Farad super capacitors. I have connected them in series-parallel to a 4 volt solar cell. I can charge them up to about 4 volts.

But that's too high a voltage for a Joule thief. I don't know if you have tried this, but connecting a JT to over 3V has a really big problem. The JT doesn't have to work, because the voltage is high enough to make the LED conduct, and in the conventional JT, the only thing between the LED and battery is the winding of the coil. If it is low resistance, then the LED will conduct heavily and overheat, letting the smoke out.

So the trick here is to have a circuit that will accept any voltage between 4 volts down to less than a volt, as the super capacitor discharges. With a conventional JT the brightness varies greatly with the voltage. The circuit I want should have a constant output as the voltage decreases from 4V to 1V.

So does anyone have any ideas?

[Watson]

LEDs Have Air Bubbles In Lens

In the ideal situation, the trigger coil picks up almost the same amount of voltage as the power source when the current in the power coil is increasing (so it doubles the cap ceiling). In the phase when the current in the power coil is decreasing, the trigger coil picks up something equivalent to that of the output voltage of the power coil -- usually much more than that of the power source, but in opposite direction. So that shuts off the transistor completely.

lanenal

And it can give you a shock if you touch both coil leads and there is no load on the coil.

I requested a return and refund, but the irascible seller refused and threatened that if I gave negative feedback and made a dispute with Paypal, they would have me banned from buying LEDs from all other ebay sellers.

I left negative feedback, and filed a claim and dispute with Paypal, and I am still waiting for the decision from Paypal. I'm very disappointed that it ended this way, but sellers have to know that LEDs with air bubbles in the lens should be rejected at the factory and should never be sold as new, top grade parts. Sellers should be selling these as 'seconds' or factory rejects.

Yeah, can you believe that? Banned! I've made only 50 transactions on ebay in more than 4 years, so is being banned going to make my life any more difficult? No. But these LEDs with flaws are being sold as top grade parts and that has to stop.

[lanenal]

In the ideal situation, the trigger coil picks up almost the same amount of voltage as the power source when the current in the power coil is increasing (so it doubles the cap ceiling). In the phase when the current in the power coil is decreasing, the trigger coil picks up something equivalent to that of the output voltage of the power coil -- usually much more than that of the power source, but in opposite direction. So that shuts off the transistor completely.

lanenal

A point to remember is that there is transfer of power from the primary winding (called power coil above) to the feedback winding (called trigger coil above) *only* when there is a change of flux, which is caused by a change in current in the primary winding. Once the current reaches its maximum (called ceiling above), there is no longer a change in flux and no longer a transfer of power to the feedback winding.

Since the feedback to the feedback winding is regenerative or in phase, once the transfer stops, the current from the feedback winding to the base of the transistor drops a slight amount. And this causes the collector current to drop, which then transfers power from the primary to the feedback winding and since it's opposing the base current, it further reduces the base current.

Thus complete cutoff of the base current happens suddenly, and the stored energy in the primary winding has no place to go, so it tries to increase the voltage across the transistor, but when the voltage gets to the point where the LED conducts, it flows through the LED. Let there be LIGHT!

And then the whole process repeats itself, at about a hundred thousand times each second. Cool, huh?

Has anyone experienced this problem? I bought some LEDs on ebay and found that they have air bubbles in the epoxy, which in my opinion is something that should be caught during inspection at the factory and rejected. The seller doesn't seem to think this is a problem. What do you think? I want my money back.