Lasersaber strikes again. A joule thief king ?

[TinselKoala]

  TinselKoala,

  I'll try your variation too. Just looking at it, it's clear that by adding another winding to the transformer, you provide a feed-back signal to the transistor, which is missing in lasertrader's schematics.
  I'm curious, did you get to make work a circuit similar to lasertrader's (using only 2 windings) ? If so, could you please post your circuit ?

Yes, if you look at the first part of this video where I do not yet have either leg of the third coil connected, you will see that I am using LS's circuit (but with a 1F capacitor and a fixed 10meg base resistor) and the LEDs do glow dimly.

http://www.youtube.com/watch?v=eqBK00tuI8Y

[d3x0r]

  TinselKoala,

  I'll try your variation too. Just looking at it, it's clear that by adding another winding to the transformer, you provide a feed-back signal to the transistor, which is missing in lasertrader's schematics.
  I'm curious, did you get to make work a circuit similar to lasertrader's (using only 2 windings) ? If so, could you please post your circuit ?

The circuit in reality is actually hard to tune... try reducing the resistor from 1M to the 100k you have in the JT sim....
I had gotten this to work in LT Spice previously...usually it's a matter of adding series resistances to simulate the wires... but was never able to get it to be the burst mode that is lowest power in simulator, was always a continuous signal.  might need the parallel capacitance set on the inductors to 100pF or so

[TinselKoala]

Scope traces from my variant:

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

Analog oscilloscopes can be very useful. A typical DSO that samples the signal periodically will miss a lot of the information that the analog scope can show.

[scifi123]

The circuit in reality is actually hard to tune... try reducing the resistor from 1M to the 100k you have in the JT sim....
I had gotten this to work in LT Spice previously...usually it's a matter of adding series resistances to simulate the wires... but was never able to get it to be the burst mode that is lowest power in simulator, was always a continuous signal.  might need the parallel capacitance set on the inductors to 100pF or so

  Can you post the LTSPice schematics that you got to oscillate ?

[scifi123]

  Here are the 2 versions side by side:
   -lasersaber's: doesn't oscillate
   -TinselKoala's: it oscillates at 106Hz

  The values for the transformer windings are just guesses.