555 Timer IC
IC 555 is a very 8 pin popular IC that is designed to work as a timer. And it is used to construct timer-based projects just like Astable, Monostable, bistable, and many more.
The 555 IC can operate from a wide range of supply voltages of + 5 V to
+18 V. This makes 555 compatible with standard digital
circuits whose voltage
levels(0-state = 0V, 1-state = 5 V) are known as TTL (transistor-transistor logic)
levels.
To better understand read the Timer and it uses
Timer
Applications
such as square
wave, ramp, pulse
generators, and one-shot multi-vibrators, etc. require a circuit
essentially capable of producing timing
intervals. Due to the circuit components count and the
delicacy in using transistors, integrated circuits(ICs) are preferred. One such most suitable and popular IC for
producing timing intervals is the 555. This IC is popularly known as 555 timer
Modes of operation
The 555 IC timer has two modes of
operation:
- as an astable(free-running) multi-vibrator
- as a mono-stable (one-shot) multi-vibrator
Block diagram of 555 Timer IC
PIN Configuration
Pin No.1. It is meant to ground the IC.
Pin No.2. It is 'Trigger' terminal. On applying a negative-going trigger voltage to this terminal.
Pin No.3. It is 'Output' terminal. A load can be connected between the output terminal and Vcc terminal or between the output terminal and the ground terminal.
Pin No.4. It is 'reset' terminal. It allows the IC to be disabled and over-rides the command signals at the trigger input.
Pin No.5. It is 'control voltage' input terminal. It is used to change both the threshold (gate) and trigger voltage level.
Pin No.6. It is 'Threshold' (a short of gate ) terminal. On applying a positive-going threshold voltage to this terminal.
Pin No.7. It is 'Discharged' terminal. It is meant for discharging an external timing capacitor during the time when the output is 'low'.
Pin No.8. It is meant for supplying bias voltage i.e. Vcc +5v To +18 V.
Types of 555 timer IC packages
The 555 timer IC is available in two package
styles metal can (TO) and DIP
as shown in Fig
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