Joule Thief 101

[jeanna]

i am not getting optimum brightness from the leds.

i built the circuit from the 3rd post of this thread combined with jeanna's instructions on page 5 of this thread.
.........

is it ok to jumble up the wires? can we establish a ratio to the windings? is it ok to use thinner wires to fit in more windings?

Yes,  most of the time, it is OK to jumble the secondary wires, but be careful not to get them too close to the primary. It can choke the system if you do.

No, we cannot establish a windings ratio.
The numbers relate to the ferrite core and each one is different.

Yes, thinner wire is great.
Just be careful not to scratch the insulation. It is brittle on the thin wire and will break out and cause spark damage and the jtc will stop working. It will first work fine then inexplicably stop when this happens.

btw, the brightness never seems the same when using the high frequency as compared to the 20mA straight through.
If they are almost as bright, then this is the real deal.

Good job, keep going!

jeanna

[tikbalang]

No, we cannot establish a windings ratio.
The numbers relate to the ferrite core and each one is different.

i was hoping there was some way of quantifying something in this circuit that can be adjusted to get a similar result over and over. can the windings compensate for a bad toroid? to what extent? how to tell if the windings were not enough? or too much?

Yes, thinner wire is great.
Just be careful not to scratch the insulation. It is brittle on the thin wire and will break out and cause spark damage and the jtc will stop working. It will first work fine then inexplicably stop when this happens.

i can confirm this. it happened to me on several experiments and the solution was to rewind the coil with new wire and to coat the toroid with nail polish.

btw, before i started painting over the toroids, i get a reading of 15kohms  to 30kohms between the toroid and the wires. it should be infinite, right?

btw, the brightness never seems the same when using the high frequency as compared to the 20mA straight through.
If they are almost as bright, then this is the real deal.

then i may already have been successful with a 1led joule thief circuit. i have built a few that were blindingly bright when LOOKED AT but can't illuminate anything useful at more than 4ft.

i did a few experiments before the holidays and one of the more successful coils were from a spool-type inductor salvaged from a CFL. the inductor itself broke so i took about 6ft of the fine wire, doubled it over to two strands of 3ft then jumble-wound it on a sharpie pen. i'll re-create it and post pics later. i'm mentioning it here because it took me a while to hunt for toroids when they were not needed at all, newbies take note!

some pre-built coils that failed: am coils with ferrite rods from two different walkman-type radios and an isolation transformer from a crt monitor.

surprisingly, CFL toroids work as-is with varying degrees of successes. i assumed they would be of the same quality since they practically have the same purpose in the CFL circuit. the plain black unpainted toroids seem to be bad performers. i found a yellow one similar to jeanna's that i will work on later with more windings, it already is bright as-is. there are a few reds and blues that i have yet to test.

CFL toroids come in different sizes and colors but the windings are more or less the same: 2T+2T/6T or 3T+3T/8T (that's "primary base+primary collector/secondary" in joule thief lingo.

i tried mixing it up with 3T+8T for a 1led jt but the difference is negligible.

thanks resman and jeanna, i'll come back later for pics and more results.

[jeanna]

@tlkb...

Have you seen this?

http://www.youtube.com/watch?v=ZnNQrYy_Bw4

I used the toroid from a cfl and took a hint from the existing turns on it, and made this light that has 42 leds.
I am able to see and if I were younger I could read by it because it is a good brightness.
There are umm 7 parallel rows of 6 series wired leds =ing 42.
I have decided that it really is no brighter than 24 leds and I suggest 6 or 7 might be good enough.
I wanted a light that would shoot in all directions (and, also I wanted to see if it could be brighter than 24 leds.)

jeanna

[shylo]

Hi Jenna ,You seem to to be the go to person for questions on this subject,..I was wondering about the transistors used, I just salvage parts from old pcb's,... does the heat from my soldering gun cause damage to the components?, because I've tried making a jt with several different transistors , none of the 2222 though, all different #'s, I just can't get it to work for me ,the torrid is out of a microwave,roughly the size of a quater but thicker.....I guess I need to know if you can re-use old components or do you need to buy new?...thanx .....shylo

[resonanceman]

Hi Jenna ,You seem to to be the go to person for questions on this subject,..I was wondering about the transistors used, I just salvage parts from old pcb's,... does the heat from my soldering gun cause damage to the components?, because I've tried making a jt with several different transistors , none of the 2222 though, all different #'s, I just can't get it to work for me ,the torrid is out of a microwave,roughly the size of a quater but thicker.....I guess I need to know if you can re-use old components or do you need to buy new?...thanx .....shylo

shylo

ALot of people use recycled parts for JTs.
I tried pulling transistors out of old  equipment but I didn't have much luck with most of them.
There are tons of different kinds of  transistors alot of them require 5V for the base.

I choose to buy transistors
it is just one less variable that I have to worry about .

Old monitors have some great parts
The flyback trnasformer works great as a JT
I save all the ferrite core transformers I find in the monitor.
There should also be some high voltage caps in there too
Just make sure you know how to ground the picture tube........it can hold a lethal  charge for years.

have you been reading the joule ringer thread?
If you want to salvage parts I would look for a store that will give you a few used disposable cameras.......most of the parts in them should  be good for JTs


gary