LEDS Flashing circuit diagram

This simple and inexpensive circuit is not just for Christmas! There are only two resistors, transistor such as a BC547 signal a "flashing" LED and a series of "normal" LEDs. The blinking LED operates as an oscillator and changing the transistor on and off, and the transistor switches all other LEDs. An (non-regulated) Power supply 12 V can be used for power.

No current limiting resistor is required in the LED string, because the forward voltages of the LED in the string is added to the supply voltage. If the red LEDs are used, with a voltage drop of 1.65 V, then 12 V supply seven alternatively, use six five green yellow (2.1 V each) or (2.7 V ). You, of course, you can always mix colors.