DUAL 3v and 1.5v WHITE LED FLASHER

DUAL 3v WHITE LED FLASHER:This circuit alternately flashes two white LEDs,on a 3v supply and produces a very bright flash.The circuit produces a voltage higher than 5v if the LED is not in circuit but the LED limits the voltage to its characteristic voltage of 3.2v to 3.6v.The circuit takes about 2mA and is actually a voltage-doubler (voltage incrementer) arrangement.
The 1k charges the 100u and the diode drops 0.6v to prevent the LED from starting to illuminate on 3v. When a transistor conducts, the collector pulls the 100u down towards the 0v rail and the negative of the electro is actually about 2v below the 0v rail.The LED sees 3v + 2v and illuminates very brightly when the voltage reaches about 3.4v. All the energy in the electro is pumped into the LED to produce a very bright flash.
DUAL 1.5v WHITE LED FLASHERThis circuit alternately flashes two white LEDs, on a 1.5v supply and produces a very bright flash.The circuit produces a voltage of about 25v when the LEDs are not connected,but the LEDs reduce this as they have a characteristic voltage-drop across them when they are illuminated.Do not use a supply voltage higher than 1.5v. The circuit takes about 10mA.
The transformer consists of 30 turns of very fine wire on a 1.6mm slug 6mm long, but any ferrite bead or slug can be used. The number of turns is not critical.
The 1n is important and using any other value or connecting it to the positive line will increase the supply current.
Using LEDs other than white will alter the flash-rate considerably and both LEDs must be the same color.


Filed Under: LED