LED Stop Watch Circuit

Engineeering Projects

ICs 555 and 4017 are well-known to electronics hobbyists. Presented here is a very interesting project of an LED stopwatch Circuit using timer 555 and decade counter 4017 ICs. This stopwatch is able to monitor time from one second to 60 minutes. It can be used in sports, laboratories, etc.

IC 555 (IC1) is the heart of the circuit. It is used in astable multivibrator mode. The special feature of this mode is that if this pin 4 of IC1  is kept at a high logic, it produces a clock pulse normally but as soon as pin 4 gets low-level logic, it stops generating a clock pulse and the output stays at a low level.

Circuit Diagram of led stop watch

In this circuit, pin 4 of IC1  is wired to the ground through a 10 KΩ resistor, and push-to-on switch SW1 is provided across the positive supply and pin 4. As soon as switch SW1 is pressed, IC1 starts generating clock pulses and the whole circuit gets activated.

AT each clock pulse, IC2, IC3, IC4, and IC5 start counting which is indicated by glowing LEDs. When switch SW1 is released, IC1 stops generating clock pulses and all counter ICs stop counting. The positions of all glowing LEDs will show how much time (pushing time of SW1) has elapsed.

IC2  counts for 1 to 10 seconds, IC3  counts for 10 to 60 seconds, IC4 counts for 1 to 10 minutes, and IC5 counts for 10 to 60 minutes. Preset VR1 should be adjusted so that IC1 produces one full clock cycle in one second.

PARTS LIST LED STOP WATCH CIRCUIT

Resistor (all ¼-watt, ± 5% Carbon)

R1, R2, R4, R5 = 10 KΩ

R3 = 22 KΩ

VR1 = 100 KΩ

Capacitors

C1 = 10 µF, 16V (Electrolytic Capacitor)

C2 = 0.01 µF (Ceramic Disc)

Semiconductors

IC1 = NE555 (Timer IC 555)

IC2 – IC5 = CD4017 (Decade Counter IC)

Miscellaneous

SW1 = Push-to-on switch

LEDs

 

5 Thoughts to “LED Stop Watch Circuit”

  1. Will
    October 15, 2014 at 5:04 am

    What is RST?

    Reply
    1. Engineeering Projects
      November 4, 2014 at 7:12 am

      RST means reset.

      Reply
      1. manish
        May 11, 2015 at 1:33 am

        hey bro what was the value for that variable resistor ???
        i mean at which value the circuit worked perfectly ???

        Reply
  2. manish
    May 11, 2015 at 1:31 am

    hey can you please help me ???
    i wanna know the value of that variable resistor , i mean at which value it starts generating the pulses for 1 sec .
    please if anyone knows tell me i need it .

    Reply
    1. Engineeering Projects
      June 25, 2015 at 9:10 pm

      Simply adjust resistor up to 1 second led glow.

      Reply

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