This circuit calls more Free Running Multivibrator work resemble Flip Flop. Which encourage itself repeatedly. The Q1 and Q2 be Transistor PNP be usable general (2N3906,2N2907, etc.) The R1 and R2 limit current that flow through LED the bilateral. If enhance the value C1 and C2 the rate something Flasher slow down. Request friends have fun LED Flasher , this please sir.
This simple circuit uses NAND Gates to alternately flash two led’s. The two 47uF capacitors determine the flash frequency. It is a good idea to use a decoupling capacitor across the power supply. I made this circuit using the components shown and it worked fine. The IC that I used is the 4011 Quad
2-input NAND Gate.
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Source:http://www.geocities.com/electronics3456/4011.html
This entry was posted on Monday, June 2nd, 2008 at 10:25 am and is filed under LED Flasher.
In the circuit diagram for the Joule Thief, the common point of the toroid is the connection at the top of the hand-wound ferrite toroid, in the upper right of the diagram. This goes to the positive end of the battery. The other two wires from the toroid go to the resistor and to the intersection of the transistor with the LED.
One other detail that you may need to know is the symbol and pinout of the 2N3904 transistor. In the symbol, the part with the arrow is the “emitter”, the “collector” is the end above it, that also connects to the LED, and the “base” is the wire leading off to the left, between the collector and emitter. (Also remember that the end of the LED with the flat side and short lead is the end that has the flat bar in the diagram.)
Read More Source:
http://www.evilmadscientist.com/article.php/joulethief
LED flasher circuit here will flash a LED using only 1.5 volts supply voltage. Normally, to make any LED lamp works, you need more than 2 volts power supply. This because LED will work only when the supply voltage is higher than its forward bias voltage, around 2 volts for red LED, and slightly lower for other color (but still higher than 1.5V). Using this LED flasher circuit, you can blink a LED with only single 1.5V cell battery. Here is the schematic diagram of the circuit:
This LED flasher works using capacitor charge pump principle. The final LED driver is 2N3904 transistor connected to a 330 ohm resistor and 220uF capacitor. When this transistor is switched off, the capacitor is charged through two 330 resistors, and when the transistor is swithed on, the capacitor will be discharged through the LED , the transistor and the power supply. At the point of view of the LED, the voltage of capacitor and the power supply is added when trying to flow through the LED, so the peak voltage when the LED is triggered is around 3 volts (but this won’t be observed since the LED will drop this voltage to its forward bias voltage value).
