NE555 Timer IC

NE555 is an Timer IC in DIP (Dual Inline Package). It was designed by Hans Camenzind in 1970.
It is an integrated circuit used in variety of Timers, Oscillators and Pulse generation operation.
It was brought into market by Signetics. in 1971, later than it was acquired by Philips. It was also known by the name Time Machine at that time.

Depending on the manufacturer the IC contains about 20 Transistor, 2 Diode, and 15 Resistor installed on a silicon chip in an 8-pin DIP.

There is also other two IC's called 556 and 558. 556 IC is a 14-pin DIP and it is a combination of two 555 IC, and 558 is a 16-pin Dip with the combination of four 555 IC.

555 IC Pinouts

1) GND (Ground) : It is connected to the ground of the circuit.
2) TRIG (Trigger) : It is the trigger point at which when the input falls below 1/3 of the Vcc, the output rises and the Pulse start (Interval starts).
3) OUT (Output) : It is the output point from where the IC gives the output.
4) RESET : It is a reset point from where we can set the timing interval by connecting it to the ground.
5) CTRL (Control) : It is an control point from where we can access the Internal Voltage Divider of the IC. Internal Voltage Divider function divide the Vcc into 2/3.
6) THR (Threshold) : When the input at THR is greater than CTRL then the inteval comes to an end.
7) DIS (Discharge) : It may be used to discharge a capacitor between the interval.

8) Vcc : It is the Vcc point of the IC where input voltage to the IC is supplied, input voltage of the IC is between 3v-5v.

Looking further this IC has three operating modes:
1) Monostable mode : The monostable operation mode is a circuit that produces an output pulse of fixed duration each time the input circuit is triggered. Taking an example of an LED, if we want any LED to glow for a specific time and then switch off then we should use Monostable mode circuit.
Its other application include touch switches, frequency divider, missing pulse detection, etc.
2) Astable mode : In Astable mode the circuit produces an output pulse of fixed duration and continuously produces that pulse once triggered.
Other application include lamp flasher, security alarm, tone generation, logic clocks,etc.
3) Bistable mobe : This is also known as Schmitt trigger,in this mode 555 can operate as a flip-flop. It's uses include latch free switches.