Joule Thief

[WilbyInebriated]

@all
someone disassembled a scanner lately ?
i found nice things in a broken one.
tiny neons tube and their source circuits.

the circuits are working with 12 volts but i think my other scanner should work on 5 volts as the power source of it is USB.
those neons do light fully on most of my jts.

yes, i posted a couple pics way back, and one not so long ago when ccfl's were asked about.

they are ccfl's not neon tubes.

the 'beerlight' uses a ccfl tube from a scanner.
yes most of the source circuits will accept a wide range of input V. i have some that will run off as little as 3.7V

[xee2]

@all

This could belong here as well.  It is from the MPI Patent topic and is very interesting.

http://magneticpowerinc.com/patent.html

This appears to be a fantasy device. I think the application was withdrawn.

[jeanna]

I have never got good results from a cap at the base resistor.

I made a bunch of tests at xee's request and because I thought it would be interesting myself.
I hadn't found any advantage either for a long time.

What I decided in the end was that it had to do with the range of the system and the size of the cap, more than anything.

I usually only start to try them when the system seems really off. Sometimes it really helps, but if the volts usually go down peak to peak. after I add the cap of any size... until I get one that is perfect.

A couple of times, when I was testing a lot of these,  the whole thing suddenly began to take off.

The resistor is parallel to the cap which means they could literally be sharing the same pin connection.

Does that help?

jeanna
edit
How many turns do you have on the jt and the secondary?
If you have 900v rectified, that is probably like my 450v peak to peak, isn't it?
Either way especially if you have 900 volts you are doing well.

Are you trying to light a tube and cannot?

[resonanceman]

I have never got good results from a cap at the base resistor.  I must not be placing it right.  Do you have any pic's of this so I can see my mistake?  Does it have to be a 104 because it seems like that is what everyone is using.  I think I can get my voltage up if I can place this cap right!

Stprue

I check  quite a few caps ......from  10pF to 5uF   


gary

[WilbyInebriated]

i thought you all might find this interesting.

"The interior surface of cold cathodes are capable of producing secondary electrons at a ratio greater than unity (amplification) upon electron and ion impact. For accelerating of the ions to a sufficient velocity for creating free electrons from the cathode material, cold cathode discharge lamps need higher voltages than hot cathode ones, causing a strong electric field near the cathodes."

quoted from the wiki, so take it how you will...

something to keep in mind when using cold cathode lamps. ie: ccfl's, neons, HID lamps (metal halide, HPS) etc.

re: thenop's 7.5kv example for neons.
this is not really telling the whole story, which really surprises me, usually from thenop it is a much more pedantic response. it's like saying my car goes 0-60... so what, it means little without the time parameter.

anyone ask about the freq.? does anyone think that high voltage/low freq. is the way to go?