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|THE 555 ASTABLE CIRCUIT|
|V. Ryan © 2007 - 2022|
When the 555 IC is used to produce an ASTABLE circuit -
it will continually pulse until power is removed. Astable circuits can be
used to flash lights/LEDs on and off or to turn a buzzer on and off
repeatedly. They are also used in many more school based circuits.
In an astable 555 circuit pins 2 and 6 are connected which means that the circuit will trigger itself continually until power is removed. The larger the value of the capacitor the longer the LED stays on and off.
|DRIVING A BICOLOUR LED CIRCUIT WITH A 555 TIMER|
|The circuit below drives a single bicolour LED. When the circuit is powered up, the LED alternatively flashes green and red.
Pin three of the 555 timer, controls which anode of the bicolour LED, receives a positive voltage. The voltage from pin 3 of the 555 timer, pulses on and off, therefore the colour emitted by the LED alternates between green and red.
|CIRCUIT WIZARD SOFTWARE|
|PICTORIAL REPRESENTATION OF THE CIRCUIT SHOWN ABOVE|