555 Timer IC Information
Learn more about the popular 555 Timer IC - the world's most popular integrated timer circuit since 1972!
The 555 timer is one of the most versatile & popular integrated circuits in electronics. There are many books devoted to it with thousands of application circuits published since its release in 1972. There are so many 555 timers in existence that in 2017 it was said that there were over 1 billion chips in existence!
Circuit Applications
Below are a few circuit applications for the NE555 we have published for many years within our printed catalogue as additional "data" on the humble NE555. The chip pin outs are also shown here:
It can function in monostable (one shot) mode, or in astable mode, where it continues running at a user-set frequency. Power supply (Vcc) can be between 4.5V and 16V DC.
Mono Stable Multivibrator
This simple circuit has a main use as a 'wave generator'. When a pulse is applied to pin 2, a pulse of T seconds is produced at pin 3. The formula for working out "T" is shown below, where R1 and C1 are the respective resistor and capacitor values in the circuit:
T = 1.1 x R1 x C1
Astable Multivibrators Fixed Duty Cycle
This is a great circuit for when a simple 50 / 50 oscillator is required. Once power is applied it is free running with a 50 % duty cycle. For more accurate timing you could use a CMOS type 7555 timer. The formula for working out frequency (f) is shown below, where R1 and C1 are the respective resistor and capacitor values in the circuit.
f = 0.7 / (R1 x C1)
Adjustable Duty Cycle
This neat circuit will give output pulses of t1 seconds in length at an interval of t2. Shown are four formulas which will add the calculation of resistors R1, R2 and capacitor C1 once the value of t1 and t2 have been chosen.
t1 = 0.693 x (R1+R2) x C1
t2 = 0.693 x R2 x C1 = 1 / T
f = 1.44 / [(R1+(2 x R2)] x C1
Period T = 0.693 x (R1 + (2 x R2)) x C1
For more information
This is a short introduction to a few circuits available to build with the 555 timer. For more detailed information try the manufacturer datasheets which contain plenty of in-depth specs .