Jewel Thief Help

team_nightstalker · Sep 21, 2007

k will do. how do i test to make sure the transistor is working correctly with a meter? don't forget i'm a newbie but a very fast learner.

Hero999 · Sep 21, 2007

Does your meter have a transistor tester?

A simple way would be to use the diode checker, hold the + test lead on the base and check that the foward voltage reads about 0.6V to 0.7V when it's hooked up to the emitter and collector.

Failing that you can test a transistor like this.
**broken link removed**
Just make sure the LED you're using works and the battery isn't flat. Don't worry about the switch just use connect the resistor to the collector and disconnect it again, LED LED should turn on and off.

mneary · Sep 21, 2007

I could be wrong, but it looks to me like you have A2 and B2 swapped. Check to see that you have 1.5 volts on the collector,, and 0.7 volts on the base.

whiz115 · Oct 22, 2007

mine also doesn't work... with ~1,35V battery i see ~1,33V on collector-emmiter and ~0,75V at base

i have posted photo on this thread...

https://www.electro-tech-online.com/threads/mini-1-5v-booster.32940/?highlight=joule

Krumlink · Oct 22, 2007

I dont see a capacitor!!!!!!!!!!!!

whiz115 · Oct 22, 2007

Krumlink said:
I dont see a capacitor!!!!!!!!!!!!

me too... what? it doesn't oscillate without capacitor?

audioguru · Oct 22, 2007

whiz115 said:
what? it doesn't oscillate without capacitor?

The Joule Thief circuit does not have a capacitor.

The base gets noise current which makes the transistor conduct a little. The collector goes low and transformer action makes the base go high which turns on the transitor fully. When the transistor reaches its peak current then the current doesn't change anymore so the transformer feed to the transistor's base drops, which causes the transistor to begin turning off and the transformer gives a negative voltage to the transistor's base which helps turn it off quickly. Then the collector voltage nearly goes twice as high as the supply voltage

eblc1388 · Oct 23, 2007

audioguru said:
The base gets noise current which makes the transistor conduct a little.

Audioguru, instead of noise current, isn't the 1K base resistor sufficient to bias the transistor to conduct somehow?

The 1K resistor value is vital to circuit operation and value depends on Beta of the transistor used. If one uses other transistors and the circuit does not work, be sure to try other values like 680R, 1K5 or 2K2.

audioguru · Oct 23, 2007

eblc1388 said:
Audioguru, instead of noise current, isn't the 1K base resistor sufficient to bias the transistor to conduct somehow?

Of course the 1k resistor supplies some base current to the transistor and turns it on since it connects to the positive supply.
Next time I will look at the schematic before typing.

whiz115 · Oct 23, 2007

what should i expect on my transistor base so i can judge that i need smaller value resistor?

Also... is it so critical not to cross the wire even once! while i'm winding the transformer?

whiz115 · Oct 23, 2007

any ideas?

whiz115 · Oct 23, 2007

ok.. finally it works!

i solved the problem by reversing the transformer wires... i also made this diagram and i hope it can help everyone who hasn't managed to make it work.

Hero999 · Oct 26, 2007

I suggested that on my first response to this thread, perhaps you need to read the replies a bit more carefully.

iONic · Oct 26, 2007

See the post in your Solar LED Forum for an alternative circuit.
https://www.electro-tech-online.com/threads/solar-blinking-led-help.32327/

Krumlink · Oct 26, 2007

see it works

On a fresh AA Alkaline battery with a white LED, I have gotten mine to run for 5 days STRAIGHT!

whiz115 · Oct 26, 2007

Hero999 said:
I suggested that on my first response to this thread, perhaps you need to read the replies a bit more carefully.

yes...sorry, i overlooked you post...

I've noticed it later on when i managed to make it work...
now i think it is going to be clear for everyone!

Krumlink said:
see it works

yeah it works..

Krumlink · Oct 26, 2007

Good, I hope it was a fun easy project for you

I have built at least 10 of them. My favorite one I stuffed inside a AA battery holder. It is really neat and compact.

In this picture it is a AA rechargeable, this was when I first put it together. right now it is sitting beside my laptop (brand new ) lighting up my room.

Wizz, do you mind if I put that pic on my website? I think it would look really nice.

CHECK OUT THE NEW PROJECTS ON IT!!!
www.freewebs.com/electronic-hobbyist

whiz115 · Oct 26, 2007

if someone makes it more clear how exactly it works....
it would be better!!!

Krumlink · Oct 26, 2007

its magic, there you go it is simple

How it works, is that the transistor makes the coil oscillate, which makes on the other wire a more increased Electromagnetic pickup, induced by electromagnetic waves, called Eddy Currents. Just look up how a transformer works.

whiz115 · Oct 26, 2007

Krumlink said:
How it works, is that the transistor makes the coil oscillate, which makes on the other wire a more increased Electromagnetic pickup, induced by electromagnetic waves, called Eddy Currents. Just look up how a transformer works.

i mean step by step details so i can understand it totaly! thanks for you try though! here's mine!

P.S i forgot.... mine also has CE approval, as you can see in the second photo!

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