Joule Thief

[AbbaRue]

@MrMag
Thanks for the scope picture.
What I find most impressive is how perfect the wave's shape is.
Almost a perfect square wave. Very similar to the output of a 555 timer.
I noticed the top of the waveform is about 2.75 divisions long and the bottom is about 2.0 divisions.

An interesting experiment would be to use a variable resistor in place of the JT. control resistor,
and note the changes in the wave form as you adjust it.
If you do so start with the resistor set to the middle so you don't have a dead short to the transistor base.

It might be a good idea to use a 10 ohm resistor in series with it just so you can't adjust it to zero ohms.
Something for anyone that is planing on using a variable resistor to keep in mind.

Anyone that wants to learn more about electronics should download the zip file at this site:
http://www.falstad.com/circuit/ 
This circuit simulator is priceless for learning electronics. 
Very easy to use just right click to get a list of components and then left click and stretch the component were you want it.
Also like the oscilloscope output it has.
I may start a separate thread on it's use and post some interesting circuits I have designed with it.

[MrMag]

Gadget,

Working on it.

Pirate,

thanks,
I think all of the above. transistor leakage, resister tolerance, coil/toroid material and of course the battery voltage. They will all have an effect on the frequency. I really think that it would be hard for two people to get the exact same results, but they should be close. As Gadget pointed out this is not a simple JT I am using here. It is a Fugi board.

xee2,

Agreed. I guess the one thing I didn't mention is that a scope will show you the true peak-to-peak voltage whereas the DVM shows the RMS voltage.

IST,

It's about time you wiped the dust off of that scope. I'm here to help any way I can. I think your gonna kick yourself  for not firing it up sooner.

[jeanna]

@xee and pirate,

I think you're right about the low battery. I was hunting around last night for an easy way to have 2 battery packs for jt without remaking another. I put 2 very nearly dead (.61 each) NiMH batteries in a 2fer holder. I forgot that a single AAA  with 1.22v remaining has a lot more strength than 2 deader ones that equal the same 1.22v.

It blinks less this morning. I was hoping for a jt based timer. It isn't that I want slow blinks. I want to have a way to change the frequency. I guess I will put that idea aside for a while.

I am more motivated to create a heater by putting lots of IR leds in a || way with my jt

Thanks

jeanna

[gadgetmall]

Jeanna thats good too . I have tons of infared l eds from that grab box i posted a picture of here but they dont produce any heat i can feel heat . there like the ones in remote controls . I fire up a couple and of coarse no lights but i can see them with My camera .You might have different wave length  as i have bunches of Laser Diodes that will burn a hole  hole in you but they produce light .. Green light red light and sort of purple light .. they are high amperage and need 30 amp power supply to run those at 4.5 volts .. curious as to your heater infrareds specs ??

[sparks]

  @Mr. Magg


    Now you can play with that duty cycle.  The time when there is no voltage changing.  The flatline dead bias line.