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555 timer ppt by vishnu

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555 timer ppt by vishnu

  1. 1. 555 TIMER IC TECHNICAL SEMINAR ON By K . Vishnu 11B61A0459
  2. 2. INTRODUCTION • The 555 IC was designed in 1971 by Hans Camenzind under contract to SigNetics Corporation. • Basically, 555 timer is a highly stable circuit used to generate time delays, or Oscillations. • A single 555 timer can provide time delay ranging from microseconds to hours. • It operates from a wide range of power supplies ranging from + 5 Volts to + 18 Volts supply voltage.
  3. 3. Pin Configuration The function of each pin of the IC is given below – •Pin–1: Ground •Pin–2: Trigger •Pin–3: Output •Pin–4: Reset •Pin–5: Control Voltage •Pin–6: Threshold •Pin–7: Discharge •Pin–8: Vcc
  4. 4. Functional diagram of 555 timer + - Threshold (2/3)Vcc R Threshold > (2/3)Vcc =>R=logic ‘1’ Threshold < (2/3)Vcc =>R=logic ‘0’ + - (1/3)Vcc Trigger S Trigger<(1/3)Vcc =>S=logic ‘1’ Trigger>(1/3)Vcc =>S=logic ‘0’ R S Q- Q 0 0 Previous state 0 1 0 1 1 0 1 0 1 1 X X
  5. 5. Modes of Operation 555 IC Timer applications can be classified into two main categories: 1. Monostable Multivibrators : Producing a single pulse when triggered. 2. Astable Multivibrators : Producing a square wave.
  6. 6. 1. Monostable Multivibrator Monostable multivibrator is often called as one-shot multivibrator.
  7. 7. 1 3 +VCC 7 6 2 8 One-shot operation R C 1/3 VCC The input trigger resets the flip-flop and C then charges until the upper comparator trips and sets the flip-flop. R S input trigger output pulse Discharge transistor ~Q Q Inverter
  8. 8. + VCC 555 48 7 6 1 3 2 R C t = 1.1RC Output pulse Trigger1/3 VCC The external components determine the output pulse width.
  9. 9. 2. Astable Multivibrator • Astable multivibrators are also known as Free-running Multivibrator. • Astable do not need trigger pulse for external to change the output. • The period for LOW and HIGH can be calculated based on resistor and capacitor value that connected at outside of timer. C charges through RA+ RB and discharges through RB.
  10. 10. 1 3 +VCC 7 6 2 8 Free-running or astable operationRB C RA R S C charges through RA+ RB and discharges through RB. Inverter ~Q output
  11. 11. Continue…  TH = 0.693 (RA+RB) C  TL = 0.693 (RB) C  Period,T = TH + TL = 0.693 (RA + 2RB)C  Frequency, f = 1 T = 1 (TH+TL ) = 1.44 (RA + 2RB) C  % Duty Cycle = [ TH TH + TL ]x 100 = (RA+RB) (RA+2RB) X100 2/3 VCC 1/3 VCC output 0 VCC Timing sequence of astable multivibrator Capacitor voltage
  12. 12. Applications  Schmitt trigger  PPM  PWM  Linear Ramp generator
  13. 13. Conclusion Hence 555 IC timer can produce very accurate and stable time delays, from microseconds to hours. It can be used with supply voltage varying from 5 to 18 V. Timer can be used in monostable mode of operation or astable mode of operation. Its various applications include waveform generator, missing pulse detector, frequency divider, pulse width modulator, burglar alarm, FSK generator, ramp generator, pulse position modulator etc.
  14. 14. References  LINEAR INTEGRATED CIRCUITS ( fourth edition) by D. Roy Choudhury-311 page number.  OP-AMPS AND LINEAR INTEGRATED CIRCUITS (forth edition) by Ramakanth A.Gayakwad-416 page number.  file:///E:/Personal%20data%20of%20me/s/555%20timer/documentat ions/555%20Timer%20Tutorial%20- %20The%20Monostable%20Multivibrator.html  http://en.wikipedia.org/wiki/555_timer_IC#Design

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