3W LED Strobe - 2 AA Batteries and Joule Thief

This LED strobe light allows 2.4V to be used compared to 4.5V for most 555 timer circuits. It uses the Joule Thief to turn on a 4V MOSFET. This reduces the number of batteries required. It is also suitable for low powered LEDs and may be used for PWM dimming.

Step 1: Materials

Strobe Light
3 watt red/yellow LED
Resistor (optional)
2 AA rechargeable batteries

555 timer circuit
Low power 555 timer (eg. ICM7555, TLC555)
N-Channel Power MOSFET (eg. IRFZ44N)
Diode (for duty cycle less than 50%)
0.01 uF ceramic capacitor
10 uF electrolytic capacitor
Resistors R1 and R2: Must be greater than 1k (values depend on desired frequency and duty cycle)
Wires

Joule Thief
2x Enameled copper wire
Toroid bead (you can find them in spent CFL lamps)
NPN transistor (eg. 2N3904)
1k ohm resistor
2 x Diode
10 uF electrolytic capacitor (at least 25 volt rating)

Comments

[aaaaoooo]

555circuit can be eliminated .........!
take the basic joule thief , replace base resistor with a 10k pot ,also connect a 47uf in parallel .. the JT itself will blink the LED

[mabster925]

can you post a schematic of the finished product I want to make it but I'm not sure how to connect the 3 parts together. I would really appreciate it.

[Ugifer]

I like this circuit - good idea to use the JT to boost the voltage for the timer.

Two thoughts that might help refine it a little:

I have seen similar voltage-boost circuits with a zener diode in parallel with the cap so as to avoid the voltage going too high at low load.  Might make a cheap and easy safety device for this circuit.

A small alteration to the JT circuit can make it much more efficient.  Attached is the schematic from a JT circuit I made for a project recently.  By putting the 1K resistor on the high side of the toroid and adding a 1n or 2n2 ceramic capacitor between that point and ground, I found the efficiency of the circuit improved around 5-fold.

Ugi

[hanlin_y]

Thanks for sharing. I'll try using the zener diode.