555 timer ic

Digital Stop Watch Circuit


Because nothing else can replace a stopwatch, So a digital stopwatch is an evergreen project that can be completed at any moment, regardless of how evolved our world’s technology is. This is also a good beginner’s pastime project. This is a straightforward project that does not necessitate a great deal of knowledge or materials. This project’s components comprise the following:

  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 stopwatch with a multiplexed 7-segment LED display based around the timer IC LM555 and the 4-digit counter IC MM74C926. A 4-digit counter, an internal output latch, NPN output source drivers for common cathode, a 7-segment display, and internal multiplexing circuitry with four multiplexing outputs are all included in the MM74C926. On the negative edge of the clock, the counter advances.

The timer IC LM555 is used to generate the clock. The circuit is powered by a 5V battery. It’s simple to put together on a general-purpose PCB. Put the circuit in a metal box with four 7-segment displays, a rotary switch S1, a start/stop switch S2, and a reset button S3.


To begin, press S3 to reset the circuit so that the display reads ‘0000.’ To get the stopwatch to start counting the time, open switch S2. Close S2 if you wish to stop the clock. At the output of the astable multivibrator, rotary switch S1 is utilized to select different time periods (IC1).

You can try building a long-duration timer circuit after you finish this one (a fun circuit to build). To try additional circuits related to timing, browse our clocks & timer circuits category.

Digital Timer Schematic Circuit Diagram

Digital Timer Schematic Circuit Diagram

As previously indicated, constructing a digital stopwatch is a lot of fun. After all, we’ve always been interested by stopwatches since we were kids. Maybe the millennials won’t get it, but if you grew up in the 1970s or 1980s, you’ll know exactly what I’m talking about. Have fun when constructing this circuit.


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