555 timers IC was developed by Hans Camenzind of Signetic Corporation in the year 1971 and is now available in two models NE 555 and SE 555

NE555 is a commercial model of IC555  with a temperature range of 0 degrees Celcius to 70 degrees Celcius and SE555 is a military-grade model with a temperature range of -550C to 1250C.

555 timer IC

Due to easy availability and low price 555 ICs are widely used in timer applications to control the led strips, serial lights are used for decoration purposes also in consumer electronics. 

Features of 555 IC

  • Operating power range of 555 IC starts from 5v to 18 V
  • 555 IC available in 3 different packages 8 pin Metal can package, 8 -pin DIP package and 14 pin DIP package 
  • Timing can be adjusted from microseconds to hours 
  • Adjustable duty cycle 
  • Operated in astable ,monostable  and  Bistable state 
  • TTL compatible due to its high output current

For understanding more on the working of 555 IC refer to the datasheet.

Pin Configuration of 555 Timer IC

The 555 timer IC comes with  3 different packages: 8 pin Metal can package, 8 -pin DIP package, and 14 pin DIP package. In which 8-pin DIP is most commonly used among the makers.

8 -pin DIP package 555 timer ic
8 -pin metal can package 555 timer ic

Functions of each of the eight pins

  • Pin 1 is connected to ground  (Ground pin )
  • Pin 2 is the trigger pin. It works on an active low trigger mechanism, which means that the timer starts working when voltage on VCC pins starts to  drop to below one-third of the input voltage. 
  • Pin 3 is the output pin. Output is either low, which is very close to 0 V, or high, which is close to the supply voltage that’s placed on pin 8. Shape of the output wave depends on how long output takes high how long to take low depends on the connections to the remaining five pinsPin 8 connected to power supply ( 5 v to 18V commonly 555 IC are provided with 5V supply ( VCC pin )
  • Pin 4 is the reset pin, which can be used to restart the 555’s timing operation.
  • Pin 5 is the control pin. This pin is simply connected to ground, usually through a small 0.01 μF capacitor to level out the fluctuation in the input power supply .
  • Pin 6 is called the threshold. When this voltage reaches two thirds of the supply voltage (Vcc) the timing cycle ends and the output falls from High to Low.
  • Pin 7 is called the discharge. This pin connects to the collector of an internal NPN transistor which discharges the timing capacitor.when voltage on this  pins starts to  drop to below one-third of the VCC voltage the output toggles from high to low
  • Pin 8 VCC pin in which we are proving the input supply range from 5V to 18V 
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arathy j