The 555 timer is a simple integrated circuit that can be used to make many different electronic circuits. With this information you will learn how how the 555 works and will have the experience to build some of the circuits below.

The 555 has three main operating modes, Monostable, Astable, and Bistable. Each mode represents a different type of circuit that has a particular output. Astable mode

All the electronics info you need to know about the 555 Timer. With over 80 different electronic circuits that you can build.

The timer is comprised of five distinct circuits: two voltage comparators; a resistive voltage divider reference; a bistable flip-flop; a discharge transistor; and an output stage that is the

The 555 can be used as an amplifier. It operates very similar to pulse-width modulation. The component values cause the 555 to oscillate at approx 66kHz and the speaker does not respond to this high frequency.

The simplest 555 oscillator takes output pin 3 to capacitor C1 via resistor R1. When the circuit is turned on, C1 is uncharged and output pin 3 is HIGH. C1 charges via R1 and when Pin 6 detects 2/3 rail voltage, output pin 3 goes LOW.

The output (Pin 3) of the 555 can be in one of two states at any time, which means it is a digital output. It can be connected directly to the inputs of other digital ICs, or it can control other devices with the help of a few extra components.

This circuit detects light falling on the Photo-cell (Light Dependent Resistor) to turn on the 555 and create a tone that is delivered to the speaker. Pin 4 must be held below 0.7v to turn the 555 off.

These two circuits make a LED fade on and off. The first circuit charges a 100u and the transistor amplifies the current entering the 100u and delivers 100 times this value to the LED via the collector-emitter pins.

TOUCH SWITCH and TOUCH ON-OFF Circuit The Touch Switch circuit will detect stray voltages produced by mains voltages and electrostatic build-up in a room. In the first circuit, pin 2 must see a LOW for the circuit to activate.