BEAM is an acronym standing for :
Biology, Electronics, Aesthetics and Mechanics
last updated Mar 27, 2007

White LED : Make a Joule Thief

Parts list :

1 White led

ferrite ring : recycled from my junkbox

enamelled wire, 1meter : from hobby motor

1K resistor 

NPN 2N3904 transistor

1.5 V battery (dead or brand new)

6 items :-)

Test drive the circuit on Breadboard  June 22, 2002

First thing first. Kindly ask your hobby motor to donate his enamelled wire.
There are 3 windings on each motor, unwind one of them : that should give you 1 meter of wire.
This is great ! The hobby motor finally do something good for you :-)


This ferrite ring was sitting in my junk drawer for decade !! I don't know why I saved it the first place :-)
Fold the 1 meter wire in half, and thread the ferrite ring as shown
20 turns should be enough
Scotch-tape the loose ends  (2 inches sticking out), then cut the wire to give you 4 ends (2 wires)
file the ends lightly and solder pin onto the end (for breadboard use)
mark the ends A1, A2, B1 and B2

Circuit is here

using 2 of 2.2K resistors in parellel to simulate 1.1K resistor
white led
+ve : coil A1 and 1.1K resistor
-ve : 3904E and white led
coil B2 goto 1.1K resistor
coil B1 goto 3904B
coil A2 goto 3904C
3904C also goto white led.......ready to go.......

That's it :-)
I do have a box full of "Dead" battery : AA, AAA and 9V !!

Using 0.82V "Dead" AAA battery and the white led is "on" !!

Using 1.583V "Brand New" AAA battery

Headlamp conversion      July 9, 2002

Major components : ferrite bead, white led, 2N3904 and 1K Ohms resistor

Oh, thanks to Mr. cheap motor for the donation of the enamelled wires (3*1m)

I set the transistor, ferrite bead and resistor side by side. And it fits perfectly into my really cheap headlamp.

Fold the 1 meter wire in half, and thread the ferrite ring for 20 turns, that should be enough

The all sit into the little "seat" :-)

not mega-bright for this one, but it is good enough to play with.

Basic concept :
Circuits quoted from :

9V battery with white leds

Constant Current Circuit @ 20mA for White led


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