Digital Stop Watch

jacky October 16, 2018 77 Comments

Make a Digital Stop Watch

A digital stopwatch is an evergreen project, it can be done at any time no matter how our advanced our world’s technology is because nothing else can replace a stopwatch. And also this is a suitable hobby project for newbies. This is a simple p[roject which doesn’t require much expertise or components. The list of components for this project include;

  1. IC LM555 – 1 nos
  2. IC MM74C926 – 1 nos
  3. Resistors of various resistance values – 19 nos
  4. Reset switch – 1 nos
  5. Diodes – 6 nos
  6. 4 digit display
  7. Start-stop button
  8. Capacitors  – 2 nos


A digital stop watch built around timer IC LM555 and 4-digit counter IC MM74C926  with multiplexed 7-segment LED display. MM74C926 consists of a 4-digit counter, an internal output latch, npn output sourcing drivers for common cathode, 7-segment display and an internal multiplexing circuitry with four multiplexing outputs. The counter advances on the negative edge of the clock. The clock is generated by timer IC LM555. The circuit works off a 5V power supply. It can be easily assembled on a general-purpose PCB. Enclose the circuit in a metal box with provisions for four 7-segment displays, rotary switch S1, start/stop switch S2 and reset switch S3


First, reset the circuit by pressing S3 so that the display shows ‘0000.’ Now open switch S2 for the stop watch to start counting the time. If you want to stop the clock, close S2. Rotary switch S1 is used to select the different time periods at the output of the astable multivibrator (IC1).

Digital Timer Circuit Diagram

Digital Stop watch circuit

Digital Timer Circuit

You may also be interested in other Timer circuits we have in our website:

1. Long Duration Timer Circuit

For more circuits, please check our category on Clocking and Timer Circuits

  • April 8, 2016

    which simulator i should use for mm74c926?

  • john muqattash
    April 19, 2015

    Hi guys i built the circuit successfully however it doesnt reset at 60 senconds and instead continues to 99 does anyone have any soulutions

    • Pim Veld
      October 19, 2015

      MM74C926 is not a clock-counter but a 4 decade ‘normal’ counter (from 0000 to 9999). If you want to count minutes and hours you have to use two ‘divide by 60’ counters.

    • Emmanuel M. Bauyon
      January 31, 2018

      yeah. thesame as mine I dont know what to do to reset at 60 seconds. do you know the solution?

  • john muqattash
    March 17, 2015

    Hi i have built this circuit for testing purposes, however i find that the teansistors connnected to the 7 segment displays overheat alot and the 7 segment displays do not light up properly do u have any suggestions for the problems and any solutions? Thanks

  • Umesh
    March 11, 2015

    How much cost of digital stop watch circuit

  • durga prasad
    January 21, 2015

    hi sir,
    can i know which ic can be used to replace 74C926? Also can i know how resistors are connected to the 7 segment display?

  • September 16, 2014

    i am also engineer of ETC….its great informative site…..good job..

  • Arati
    July 10, 2014

    If any use of RTOS system in electronics industry. Please tell me.

  • Mark Odyssey Rodel
    April 17, 2014

    After making the circuit we encounter some problems, instead of just counting from 0-59 it continuous up to 99. Any idea how to fix this.

  • poonam
    March 20, 2014

    i want pcb design.please send it

    • poonam
      March 20, 2014

      what can i use as a replacemeent for MM74C926

  • iksir
    January 9, 2014

    you know what, I’ve done with this by using 74C926. But, it’s just counting. When it’s 00.59, it just continue counting til 99. it should be 01.00 if it’s a stopwatch as you wrote at the title.
    do you know how to fix it?

    • November 22, 2016

      sorry my friend i could not find the solution.

  • digit
    October 31, 2013

    what can i use as a replacement for MM74C926??

    • Seetharaman
      November 1, 2013

      It is a special purpose custom made IC has no replacement equivalent.

  • […] Or maybe this one:…nd-programming Or pin 3 on the LM555: Or the 4MHz crystal needed here: http://www.electronics-project-desig…TimeClock.html Or Y1, […]

  • yashu
    October 9, 2013

    Wat will be the cost of tis project..!

  • Johary Ambalagan
    October 5, 2013

    …were finally finished this project!!! but the IC is so expensive-

    • Mohsin
      November 15, 2014

      Bro does this project really work?

  • sunilnadh
    September 30, 2013

    PLS wish me to get success

  • Renuka B. Khatke
    July 16, 2013

    What will be the price of overall project.

  • Nedugod
    May 30, 2013

    Can i use Mm74C928 instead of 926

  • chandan
    April 7, 2013

    can you mail me the pcb layout

  • chandan
    April 7, 2013

    can you mail the lay pcb layout

  • bharti
    March 17, 2013

    we dont get the ic mm74c926 let we know there is any replacement for it

  • shalaka
    March 17, 2013

    we dont get the ic mm74c926 let we know there is any replacement for it

  • remiz
    March 6, 2013

    i would like to know how this circuit works????? anyone help me plzz

  • MA
    February 24, 2013

    How are the resistors connected to the 7-segments ?

    • Madhu
      September 2, 2013

      7-segment display as 7 terminal, no 15 port of the IC is connected to the “a” terminal of the 7-segment display through resistor. Like that all the terminals of the IC is connected to the respective terminals of the 7-segment display. TO know more about the terminals of the 7-segment display check this link

      • amrit
        November 20, 2015

        Using raspberry pi GPIO pins to turn on a LED by giving high signal,and a switch as an input to turn it off.ith each time led ON it should increment the counter of 7 segment display , now the problem i m facing is that if i blink the led with a program it should reset the counter of 7 segment display using the same data lines . for doing this i have to make an additional circuit. kindly give some hints to proceed.

  • lim
    February 6, 2013

    what is the alternative ic for 74C926?

  • zaini
    November 18, 2012

    i’m done doing this stopwatch..but can’t operatingw well…the problem is cannot start….when reset,the LED show a number 8888…so what is the problem?

  • parinay
    October 28, 2012

    sir ,how we can assemble these project if we don’t know d procedure .so ,plz rply soon i wanna to module these……

  • zaini
    October 23, 2012

    how to make large size stopwatch?

  • Siddheshwar
    October 12, 2012

    sir is there any replacement for ic mm74c926?

  • bharath4
    October 5, 2012

    hi can i use any other ic’s instead of mm74c926.if there any plz reply me…….

  • Aditya
    August 23, 2012

    i’m makein this ckt on EAGLE.
    but m not understanding which switches to use.
    plz can you help me?

  • din
    July 5, 2012

    hi, i am student of unikl miat located at sepang .. i learning mechanical and currently doing my fyp that need automatic digital timer or stopwatch. i really do have almost zero skill and knowledge obout this item. if u may .. could u pls elaborate this device for me . tq
    ur help are highly appreciated .

  • Faisal
    June 15, 2012

    HITEC UNIVERSITY STUDENT:I have Made digital stopwatch using this cct . and it is working properly.the problem is that IC2 is expensive (Rs 800) and its not available easily in can use any seven segment display but it should be common cathode. its above 3rd pin should be ground.2 pole 4 position rotary switch should be used pole is connected with 22k resistor and other any two terminals with position 1 and 2.disp1 in this cct of milli sec disp2 is sec disp3 is minute.ground should be given properly use small wires as you can for breadboard.

    • zaini
      November 18, 2012

      buy from how?

    • Usman
      July 9, 2014

      AOA. i am using proteus to design the stopwatch. Can u tell me which tansistor to use? The bc547 bipolar or the NPN.
      Also from where did u buy the IC? I am assuming you are living in the Isl/Pindi region.
      Also how do I connect the 7 segment displays with each other?
      Plz reply soon

  • sruthi
    May 25, 2012

    pls tell me the applications of the chip we can expand this project?

  • sruthi
    May 25, 2012

    plaese send me the required functions of the chip IC1 LM555,and IC2 MM 74C926.PLEASE INCLUDE WHY THE CAPACITANCE ARE IMPORTANT IN THIS CIRCUIT.

  • ashraf
    May 10, 2012

    i have made this circuit but its not counting..its showing 0000 reading but not counting..
    please help me

  • Paul
    May 3, 2012

    T1 is not listed on the parts list and T2 is there a suitable sub for this part? The 7 segment displays need pinout connections. Also part# for the 7 segment displays can’t be found is there a sub for this also. Thanks

  • April 16, 2012

    plz snd the question for oral exam on interval measurement using 74c926

  • April 16, 2012

    Plz snd the questions and answers of project on internal measurement using 74c926(digital stop watch)which will be asked for oral examination as early as possible.

  • seetharaman
    November 4, 2011

    Hi Naish use the following data for your connections

    November 2, 2011

    i m not finding hw to cofigurate resistor with sevensegment…plz help me..

  • asichi
    August 15, 2011

    okey..thank you very for responding..!!..

  • seetharaman
    August 13, 2011

    Hi Asichi MM74C926 is an LSI with lots of digital circuits integrated into it. with discrete 741s you cannot build up the required circuit.

  • asichi
    August 12, 2011

    instead of using 74c926… can i use 74ls series of ic.??
    if yes,.what type of 74ls can i use.?

  • Reques
    June 5, 2011

    Dear Friends,
    It is humbly requested that please show your any contact or email espacially email of gmail account becasue my email id is also in gmail so we can contact easily.



  • pinky
    April 7, 2011

    i have made this circuit but its not counting..its showing 0000 reading but not the 555timer is not working with LED but its absolutely okay
    plz help

  • February 21, 2011

    i want pcb design of digital stopwatch.please send me.

  • Marcello
    January 2, 2011

    I cant find mm74c926 in multisim too. what can i use instead of it ??

  • xeeshan
    November 27, 2010

    sir, plz send me more details of itz component and a fine circuit plzz i will be vry thankful to u sir….

  • Leary
    September 23, 2010

    Please send me the pcb layout. tnx

  • rashmi
    September 3, 2010

    i wanted the digital stop watch uing bcd’s and simple circuits

  • sally
    June 30, 2010

    i have to make it on multisim but i cant find mm74c926 in multi. what can i use instead of it ??

    • Mohsin
      November 11, 2014

      I am also trying to do so.. have you done??

    October 8, 2009

    oh man… this circuit saved me from my subject,it really worked, and it impressed my instructor..

    it has two functions… the regular stopwatch and the split type.

    though the ic 74c926 type is expensive.

    i have pics on my facebook account of this project.

    • vitu
      August 10, 2012

      i couldnt get ic there any alternative…

  • ankush
    September 18, 2009

    piease send the good circuits to my email id

  • cesar peralta
    April 16, 2009

    RESET PROBLEM: why won’t it reset when the timer is on stop mode?

  • joseph aranas
    April 10, 2009

    sir, i tried this circuit of yours digital stop watch, and it works fine….thing is the hundredth of a second works, but when it comes in the minute counting, it doesn’t stop at 60 but goes to 99…what to do…please help…thanks

  • Jaitun
    November 17, 2008

    I want to khnow scope of digital stopwatch.

  • vivek
    October 12, 2008

    i want detail info about project. pls help

  • August 23, 2008

    how can digital stop watch works it is a MM74C926 decade coUnter IC how it could count i me to say a digital stop watch will count 60sec and then reset.

  • chumisa
    April 27, 2008

    since a 74C926 counter is not there when simulating the circuit for the stopwatch, can a up/ down counter be used instead of this one? or which counter can be used?

  • dumudu
    March 10, 2008

    please send me the pcb of led drivers

Leave a Reply