Joule Thief

[TinselKoala]

@powercat, thanks, I need to confirm the speculation about the duration with testing with a real 10F cap, but I just can't afford one now. I can get up to about 3.4 Farad with what I've got on hand.

@gadgetmall...that is really cool result, I can't match that yet, I'm not seeing a real recharge although I do see climbing supply voltages on occasion. I have found that if _either_ lead of my bench PS is connected to the circuit, even if the PS is turned off, I get a nice strong light as long as the Earth ground is also connected. I'm finding that any connection to a mains-connected instrument screws up the evaluation; this makes me wish I had a fully isolated scope to play with like the Fluke 199 or some other portables. Alas, the one I used to borrow is not available right now.
If you use a cap in place of the NiCad, do you still see this kind of clear recharge effect?

@all: I am thinking of a circuit (for duplication of LTseung's work)  that will automatically recharge the reservoir cap by briefly connecting it to a battery when the cap's voltage drops below a set limit. I imagine an op-amp comparator, 741 or similar, looking at the cap voltage and comparing that to an adjustable reference voltage. When the comparator flips state, it will trigger a monostable 555 to deliver a pulse (also of adjustable duration) to the gate of a mosfet that will make the battery connection to the cap,  for the duration of the monostable pulse. Cap voltage rises and comparator flips, monostable timer resets when its duration is complete, and system is back at "run" state running on the cap only.
What do you think of this idea, and can anyone help with the circuit design?

[gadgetmall]

TK. Yes and No with the 1.2 volt battery removed the light stops bit the voltage stays at .850 and the circuit is still running but no 220 volt light so i think it i try a different led on there it might light it . Also a ground and a small wire on this setup is on the to do list . If you built a crossover with the diode feedback try another diode the opposite way on the other side of the load to the other primary with and with out a disk cap and you will see it rise and not fall .i get even better results with  .00022 or 220pf   also .0001uf

[NickZ]

  Gadget and All:
   I have made very close to the same circuit, and I am testing it now.  Although I'm using the TIP 3055, and a 2n4017, and I'm connecting a 1N4148 diode from the secondary coil to the TIP 3055 negative rail. A big magnet is under my ferrite rod coil transformer, which is lighting a 9 led bulb. Some of the leds are burnt on this bulb but nine are still lighting
The diode connection makes a big difference in additional brightness, but the 6 AA batteries power pack gets slightly warm after running the device for a while.
  I'll run this all day and see what happens.
                                                                      Nick

[TinselKoala]

@Nick: The white PVC tube is your battery pack?
And what happens if you remove or move the big magnet while the circuit is in operation?
Diode connected at negative rail to which end of secondary, and in what polarity?

FWIW, the 10 mH inductor that I got from a TV chassis and added a secondary to, for my 4 NE2 HVJT using a single 2n3055, has a magnet attached to one end of it, it came that way out of the TV. And another, smaller version from a smaller TV set, that I am about to wind with a secondary, came with  _two_ magnets, one on each end of the ferrite spool bobbin.
I think this is done to bias the core, or to move it closer to full saturation, so that only little currents in the coil can push it over the edge. This bias will be unidirectional with the single magnet, I think: current in one direction saturates, current in the other "desaturates" the core. With two magnets there are lots of combinations for effects, more than I can consider right now, need more coffee first.

[gadgetmall]

Tk . are those old color Tv's ? I am an x tv repair man  and that is the delay line ?. I did not know they had magnets on them .Now i wil have to hunt for a relic . I threw hundreds of them away three years ago ;(

NickZ .. good luck . i think you are using to much juice and that light is bright though . Yes let us know the start volts and the end volts ...


Mine has climbed to 1.272 from 1.228 and still rising . Not much light on 8 led 220 bulb but the amazing thing is it is a COLD circuit like really colder than the room if i shoot it with a laser thermometer. The other ones ran a few degrees above ambient .

Mine is boxed now and setting in my room by itself . I will check it threwout the day to confirm my findings..

In the meantime i am replicating my replication with the other homemade coil .

TK . if you have a spare delay line i'll trade ya for 4 nice germanium transistors (antiques)  they are 39 bucks each now.