Generating time delay with 555 IC

Summary

 

This circuit based project demonstrates the working of 555 timer in astable mode to generate pulses of time period 0.5 second. This pulse can be further used for anything where we need a pulse such as to blink a LED or to create fashionable blinking lights. Image below shows internal circuitry of NE 555 timer which can be used in astable and monostable mode:

NE555

Description

This circuit of this project makes the use of timer IC NE555 which produces a constant square pulse of a desired frequency. This pulse could be either triggered or could be produced continuously depending upon the mode of 555 we are using. The two mostly used modes of 555 are Monostable and Astable. Here it is used in the astable mode with time period of half second, with high time period of 0.333 seconds and low time period of 0.166 seconds.
 
For astable mode total time period is [ln2C*(R1+2*R2)] with high time period as [ln2(R1+R2)*C] and low time period as [ln2(R2*C)]. Here R1 is the resistor connected between VCC and pin7 (discharge pin), R2 is between pin7 and pin2 (trigger pin) and C1 is the capacitor connected from pin2 to ground. For 555 to function in astable mode pin2 and pin6 (threshold) pin must be shorted. Reset pin is connected to VCC.
 
The output of 555 is taken at pin3 which is in the form of square wave and is then fed to lighting circuit which glows when output is high and stops when it becomes low; there by producing pattern of blinking lights. By varying the value of R1, R2 and C1 square waves of different time periods can be obtained.                    

 

Circuit Diagram

Components
Resistor Image
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 Resistor

Resistor is a passive component used to control current in a circuit. Its resistance is given by the ratio of voltage applied across its terminals to the current passing through it. Thus a particular value of resistor, for fixed voltage, limits the current through it. They are omnipresent in electronic circuits.

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Capacitor image
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 Capacitor

 

 

Capacitor is a passive component used to store charge. The charge (q) stored in a capacitor is the product of its capacitance (C) value and the voltage (V) applied to it. Capacitors offer infinite reactance to zero frequency so they are used for blocking DC components or bypassing the AC signals. The capacitor undergoes through a recursive cycl...

555 Timer | IC 555 | NE555
  • 92,174-Reads
 555 Timer IC

555 is a very commonly used IC for generating accurate timing pulses. It is an 8pin timer IC and has mainly two modes of operation: monostable and astable. In monostable mode time delay of the pulses can be precisely controlled by an external resistor and a capacitor whereas in astable mode the frequency & duty cycle are controlled by two external resistors and a...

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