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THE 555 TIMER - ASTABLE CIRCUIT

V. Ryan © 2002

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.
Look at the circuit drawn below. Pins 6 and 2 are connected and go to the negative (0 volts). This is the easiest way of recognising that a 555 IC has been set up as astable.