Joule Thief

[Mk1]

@all

This a great video again from kubikop http://www.youtube.com/watch?v=djskrNakKSc&feature=related

[Mk1]

@all

i made some test on different toroid they all light the led in the normal jt way, but on same type and position on the pickup coil you got a big gap in results, some observations.

All test on 2n3904 , all results after rectifier so dc reading.

Yellow white(side) , with 1k got 7 volts , the best resistor is 7 ohm , got 32 volts. (xenomorphlabs, slayer007 , you should try changing the resistor value)

The green Blue side , with 1 k got 22v , the best is 55 ohm it gives 45 volts

The forest green , with 1k got 67 volts, the best resistor is 1k! (this one is the stuff of my dreams)

@ist

Toroid have inductance rating , yes the coil but the toroid and the freq is important.

I also found a chart of the wire needed to make a turn around the toroid, we still need to break the size code , but it still is nice to have.

[electricme]

@ all
I drove into town today and bought a little device to try and get the best output out of my torrds.
What I got was a "Resistance Wheel", or Resistance Substitution Wheel". It cost me $19.95 Australian dollars, would be about $10 American.


This device has inside it all the resistors from 5 ohm to 1Meg ohm, I clip the red and black clips where the 1K resistor goes at the base of the transistor and after applying power, I turn the wheel until I get the best possible setting, against the best output of the torid.

Look at the scale, the pointers arrow will point to the resistor which is the one putting out the best voltage.

I believe there is a Capacitor wheel as well, I will get one of those as soon as I can.

jim

[Mk1]

@electricme

Nice find !

I personally use a 30 turn 5k trim pot, so its a bit easier to dial just right.

[electricme]

@ all
This is off the JT thread but I think we should all know how to repair a broken instrument, involving the meter pointer.
Over the years I have been involved in electrical work, nothing is more frustrating than the "needle" breaks off for one reason or another.

I had made a hole in my 24V DC distribution switch board, mounted my expensieve Ammeter, low and behold, the pointer indicator had snapped off, oooops i daisy.

Upon inspection, the pointer had corroded, being made of aluminium, it couldnt be soldered..

Closer inspection, revealed the pointer was hollow all the way up its shaft, this makes it much easier to repair.

I cut a suitable length of christmas tree thin glass fibre, I fed this up through the broken shaft, during this process, the shaft broke into 3 more pieces, I fed the other end into the movement section. Using superglue, a tiny droplet was applied to each rejoined shaft section.

This instrument will not be accurate anymore as the moving pointer will be heavier than its designed pointer.

But I managed to salvage my expensive meter.

jim