hey mad scientists

me again..

the joule thief... is there a limmit on the voltage it can be used on?
and/or how could i sorta make one at 6 volts at quite high amps..
as it would be yet another usefull device for my nice 6 volt motorbike
beef it up... a little hehe

i have lots of parts at my disposal... u have a huge ferite ring allmost like the size of a car tire
its 14' inch across and is.... -really- heavy
allso brought a huge job lot of differnt LED's from Ebay for £100... sounds alot for LED's but
when i got 41000 LED's of all differnt types, size, brightness and colout i think it was well worth it
plus i live close to the seller so i never had to pay postage

Rember! Raid old TV's, VCRs, radios, computers,..... anything with electronics that have broken for parts!

Release the Evil Mad Scientist from within!!

-
John-the-Dragon-Man

There's a certain part of me that wants to tell you about switching power supplies in general, and how and why they are designed the way that they are... but if *I* had a 14-inch ferrite ring, I'd also want to build a Joule Thief out of it.

What you need to know is that while the current *may* scale under the right circumstances, the voltages do not scale quite so obviously. It is important that the voltage input to the circuit be lower than the "forward voltage" of the LED that you are using. Otherwise, the current just flows through the LED, not the transistor, and so the transistor can't do anything, and the Joule Thief circuit does not do anything, even though (or rather, because) the LED lights up. One way around this is to use multiple LEDs in series, which increases the effective forward voltage.

Also note that *all* of the components involved may be damaged by high currents. If you need to scale up, you might consider replacing some or all of the components with equivalents that are designed for higher current.

Hummm,
guess I could always go valve technology j/k... hehe

so here's the picture.. picture a guy wrapping half a mill cable around a ferrite ring... he has an almost unlimited amount of wire.. how long does it take?
Hours!

I was bored.. I do and make crazy things when im bored

I've made a miniature joule thief, its really impressive, so impressive intact I made 14 and that's just with components lying around my room
ive made 14, 3V "packs" out of them which is nice and simple, just a battery case with a 9v connector on the end so you can change the battery type box(AAA, AA, C, & D ect.) put the joule thief in a small box and just use an elastic band to hold them both together.

ive allso mde one for my mobile phone. i have 2 batterys for my phone but one got so bad it wouldnt charge anymore so i used that one to up all the components in and piggy backed the new battery. when the new battery goes flat put in the joule theaf case(old battery) and you have enough power you get 1 - 2 bars of battery life left enough to make a 17 and a bit minute call!!!

I have quite a lot of old computer switching power supplies there good for parts
and the caps are fun too.
you guys should get one of them free chat room things, I would never be out of it.

Sounds like you've been having fun!

The trouble with a chat room is that we'd get even less sleep. (It's already hard to keep up with all the different projects.... We avoid phones, IM, IRC, TV, and so on.... else nothing would get done.)

Yes i can agree with that,

i have 5 msn messenger, 2 AOL, 3 yahoo and 1 ICQ addresses and i host a chatroom on WinMx and a teamspeak server

so lots of fun.

i still play.. electronics , radios and computers are my best pass time

I made the Joule Thief and was ecstatic when it worked the first time. Being a high school student with hardly any electronics experience, I was very proud. I'm working on a project for a competition that requires an electric vehicle to move a specific distance between 5 and 10 meters, with the exact distance to be announced at the competition. I want to use the LEGO RCX so i could make a simple program to run the motors for a specific time depending on how many times i push a button. The only problem is that the competition limits the battery usage to 4 individual cells rated at 1.5 volts or less each, and the RCX runs with 6 AA batteries. I thought that that using the joule thief I could use 1 battery to generate 3volts to make up the difference, but it is being very finicky. I replaced the LED with a diode so i could use the Thief as a voltage source, but when i use my multimeter to measure the voltage, it steadily climbs to about 10V, but when i connect it to the RCX and turn it on, the voltage from the Thief drops to about a volt. I was wondering if there was a simple way to fix this. My resources are limited, i.e. Radioshack and scavenged parts from old electronics. Thanks a bunch for any input! -Nick (i posted the above paragraph as a comment on the Joule Thief project site) also, here's the link to the PDF with the rules http://www.soinc.org/events/sample/ElectricVehicle_C08_v13%20_1_.pdf

The Joule Thief acts as a switching power supply that converts a lower voltage into a higher voltage. It is, however, a rather weak little power supply. It cannot supply much current at a higher voltage-- only a few mA on average. When you try to draw more than a few mA out of it (and the RCX may take hundreds of mA, especially when running motors), the voltage that is supplied will drop down until an equilibrium is reached-- where the power supply can actually source enough current at that voltage.

What you really want for this application is a "boost mode switching power supply." That's a setup that efficiently converts your lower voltage into a higher voltage. In essence, this works like a transformer, but for DC voltages: A higher current at a lower voltage is used to produce a lower current at a higher voltage. Now, can you get one of these at Radio Shack? I don't know. Maybe, if you're clever. You can certainly build one that's so-so using a 555 oscillator, an inductor, and a few other simple components, but it may be more work than you really had in mind.

I don't mind the work, but I do have to have this finished by Friday. If the parts I need to build the "boost mode switching power supply" (or similar), can be bought at radioshack or scavenged, and then assembled in a few hours, I'll happily assemble the circuit. I would also document the building and post it somewhere so others could use it. I'd love to be able to contribute to this site. Thanks for your response! -Nick

How about a 555 voltage doubler? I *think* it will produce enough current, and you should be able to get the parts at RS. Try it early, rather than later. It should take 4.5 V (Three cells) up to 9 V (equiv of 6 cells). Schematic

Hi John and Windell

I built a larger Joule Thief circuit useing a Lg. Ferrite Torrid and wrapped it w/ telephone wire. I am useing it to power a 12v car light bulb, my power source is a 9v battery and boy does it get bright,

here is the info on the Lg. Ferrite Torrids
http://www.youtube.com/watch?v=FD77lY9xG6k

here is the info on the of the Joule Thief that Pirate88179 emailed to me
http://i247.photobucket.com/albums/gg149/davidmann007/PiratesJouleThief.jpg

I hope this info helps

Dave

Hi John and Windell

I built a larger Joule Thief circuit useing a Lg. Ferrite Torrid and wrapped it w/ telephone wire. I am useing it to power a 12v car light bulb, my power source is a 9v battery and boy does it get bright,

here is the info on the Lg. Ferrite Torrids
http://www.youtube.com/watch?v=FD77lY9xG6k

here is the info on the of the Joule Thief that Pirate88179 emailed to me
http://i247.photobucket.com/albums/gg149/davidmann007/PiratesJouleThief.jpg

I hope this info helps

Dave