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;
- IC LM555 – 1 nos
- IC MM74C926 – 1 nos
- Resistors of various resistance values – 19 nos
- Reset switch – 1 nos
- Diodes – 6 nos
- 4 digit display
- Start-stop button
- Capacitors – 2 nos
A digital stopwatch built around timer IC LM555 and 4-digit counter IC MM74C926 with a 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 stopwatch 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).
After finishing this circuit, you can try building a long duration timer circuit (a fun circuit to build). You may check our category of clocks & timer circuits to try more circuits related to timing.
Digital Timer Circuit Diagram
As I stated above, a digital stopwatch is a very fun circuit to build. After all, a stopwatch is something we have been fascinated by in our young days. Maybe the millennials won’t understand, but if you are someone from the middle of the 1970’s or 1980s, you will understand what I am saying. Enjoy building this circuit and have fun.