Joule Thief

[Artic_Knight]

it appears to be a standard joule thief 2 coils a mosfet and a resistor capacitor tank but the difference is its made with a mosfet and was patented in 1988   in this situation they have modified the base coil so that the resistor and capacitor tank is directly touching the base of the mosfet or "gate" and the coil is after. the coil however was set up so that it could osilate in a AC fasion. so a slightly different placement there. again however the base or gate coil is magnetically tied to the primary winding or source winding allowing it to be a blocking oscilator. the voltage however is down to 0.1 which is impressive!

[void109]

Wound a BJT on a magnetics square permalloy toroid, pretty typical setup with minor changes last night.  Out of curiousity I wanted to check the battery level over a period of time, not methodical just ad-hoc.

T = 0 hours Initial voltage: 1130mV
T+2 hours: 1137mV
**disconnected oscilloscope and voltage meter**
T+13 hours 1124mV
T+15 hours 1128mV

You can see I was suspect that the increase in voltage was somehow from the scope or voltage meter, and when I checked many hours later a reduced voltage supported that hypothesis, but I let it run further and I see the voltage is again slowly rising.   This setup has 8 leds very dimly lit.  I will continue to let this run and if it continues this behavior I will start logging data at regular intervals and draw out the exact schematic and post videos.

My question is - is this behavior typical of a bjt or jt circuit (still new to the circuit)?  The battery is a 1.4v ni-cad rechargeable.

Thanks!

[jeanna]

  Hello, anyone feel free to answer my question, Thanks !!!

     If I had a Joule thief  putting out say... 60 Volts at around 10-25 mA's , I should be able to put
     10-15 LED's in series and all should light up nice and bright !!!

     Would that be correct ?  as long as each LED gets about 3v or so.

In my joule thief experience, the series leds need about 7-10 spiky volts to look as bright as they would from a straight dc circuit.
If I had 60v output from the secondary of my jtc, I would start with 12 leds and expect to take one or 2 out for full brightness, but at 60v 15 leds would most certainly all turn on.

I have a question for you, now...
What do you mean by saying the jtc puts out 10-25mA?
How are you measuring the output mA?
Or, are you measuring the circuit draw?

thanks,

jeanna

[stprue]

@viod109

please post this on the BJT topic!  I just posted a circuit that will run off an calculator solar/maxcap indefinitely.

[nievesoliveras]

As promised

Jesus