In this post we are going to construct a simple LED stopwatch using IC 555 timer and IC 4017 decade counter. The elapsed time is indicated by LEDs which illuminates in a sequence.
Stopwatch is very important piece of equipment in sports, cooking, laboratory, medical etc. They are used to measure short period of time accurately.
Most of the people use their wrist watch or wall clock to measure time, but doing so they may end up in confusions and may lead to human error while noting the elapsed time.
We can conclude that normal wall clock or wrist clock can’t match the functionality of a stopwatch where it shows elapsed time directly without any confusing mind calculation. Being an electronic enthusiast we can construct one without much difficulty.
The proposed design is inexpensive to construct and very easy to operate. It consists of one IC 555 and four IC 4017. The IC2 consist of 10 LEDs which count from 0 to 9 second.
The IC3 consist of 6 LEDs, each LED indicates 10 second. The IC4 consist of 10 LEDs which counts minutes, each LED indicates 1 minute.
The IC5 consist of 7 LEDs, each LED indicates 10 minute and the illumination of 7th LED indicates completion of 1 hour and all the LEDs start from begining.
The IC 555 is heart of the circuit which gives clock signal to decade counter ICs to increment position of LED’s illumination. To operate the stopwatch we just need to press the push button (push to ON & push to OFF) to start.
The LEDs starts illuminating on and off in a sequence and when you want to freeze the clock, just press the button again. This will stop the IC 555 generating clock pulses and thus all the LEDs stay in current position till we turn off the supply