INTRODUCTION: This is a simple sequential circuit that counts in upward direction when the input across it becomes high (i-e: on rising clock edge) Each output becomes high as the count advances. The reset input is adjusted to low condition for normal operation of circuit.




1) Resistor  33k, 47k, 1k
2) Capacitor 0.1Mf. 2.2mF
3) IC 555 TIMER
4) Counter IC 4017
5) LEDs 10 leds (any no)
6) Battery 9 volts

WORKING: The basic purpose of this circuit is to produce the sequential flashing line of leds .This circuit is made to light up a led  for a period of 1 second and the cycle continues giving the running light appearance.  It uses two ICs one is 555 timer working as a straight oscillator another is 4017 decade counter wired in astable multivibrator mood. Resistors and capacitors are used as timing components and the output pulses are obtained from the output pin of 555 timer.One resistor is used for setting frequency of a basic astable or free running pulse generator with 555 timer IC as main. The pulses are provided to the input pin of the Johnson decade counter ( IC 4017)  when 555timer generate the high frequency the decade counter provides positive output voltage sort by the position according to input from 555 timer.8 inputs of decade counter are used to light up the leds the 9th is used to reset the counting sequence so that the cycle continues itself to repeat  with the help of capacitor each led remains onn for 1 sec. when one led gets off the next gets on. This cycle repeats resulting in a running light appearance. To control the running speed of the leds potentiometer is used.

APPLICATIONS: This circuit is used:

  • To synthesize the sound effects
  • To teach electronic theory and basic circuit construction techniques.
  • As dancing light.

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