This circuit can be worked as a clock in this counter will advance after every one second. When you provide power supply it start its counting from zero and you can stop the timing with the help of switch. It can be used while cooking or while doing exercise. It can used by students preparing for competitive exams. You can also use this circuits during playing game like teams have to complete the task and the team which have done it in shortest period of time first will be the winner. In such type of game we can easily record the time of individual team. In this the team which finishes the task just has to flip the switch S2 and time gets recorded. This circuit also calculates the time in minute. In this circuit when 99 seconds completed a musical sound is heard and it will sound till 50 seconds and stop again for approx. 40 seconds.
A stopwatch is a timepiece that measures the amount of time between any two occurrences. Usually, at the first occurrence, the stopwatch is started while at the [[wysiwyg_imageupload::]]second it is stopped. To use it again, a reset option is also provided with the stopwatch. The total time elapsed can thus be obtained. A stopwatch is very commonly used in racing competitions and other gaming activities. The circuit given here is a digital stopwatch that displays time on four seven segment displaysusing 8051 microcontroller (AT89C51).The stopwatch keeps the track of time the same way as a simple digital clock does. It is basically an up time counter that starts from 00:00. The control options are provided by means of tactile switches which are active low. This circuit uses three such switches for following operations. Read more to find out how the circuit is made and how 8051 microcontroller can be programmed to do the task of a stopwatch.