TREE

This is a 555 led flasher circuit this circuit will blink many LEDs and give rotating effects. The circuit is very easy to build, 555 timer IC is very common now a days you will find it easily. The circuit uses only 3 volt to perform its task, small 3 volt button cells can also be used and it will last longer because the circuit has low current consumption. Upper 555 IC in the circuit is used as multivibrator and the lower 555 IC is working as a trigger pulse inverter.  Source http://www.circuitdiagram.org

A magnet is placed on the door and a magnetic reed switch on the door casing so when the door is closed the circuit is disabled. When the door is open, the LED flashes VERY BRIGHTLY—when closed, the circuit is disabled in such a way that it draws virtually no current for maximum battery life. Door Ajar LED Light Schematic Bill of material 555 door ajar BOM How it works The flasher is the standard 555 oscillator circuit that drives an ultrabright white LED for daylight visibility. Repetition rate is about 2hZ and the duty cycle is about 10%. Peak LED current is 60mA, but average is 6mA. Since the door is supposed to remain closed most of the time, the circuit power is controlled by a 2N7000 N Channel MOSFET. When the reed switch is closed (sensing the magnet), it shorts out the gate drive signal to the transistor and turns off the oscillator. At this time the battery drain is only 9uA. Note that there seems to be no convenient way to turn off the 555 in such a way that it does not draw ...

This simple LED flasher using transistor,  an LED flasher can be made ​​that can be used for example to simulate the existence of an alarm mounted in a vehicle driver. LED Flasher Using Transistor Circuit Diagram: The circuit is a relaxation oscillator built around transistor T1 Unijunction that provides repeated pulses with a duration of a few milliseconds, Darlington transistor T2. When the contact is closed the LED is blocked through T3. The circuit has a current actual consumption of only 2 mA. Resistors R1 and R3 will be resized to compensate for higher tolerances resulting from manufactured Unijunction transistors. Do not use in the assembly of high power LEDs (current peaks should not exceed 250 mA).