Help Me Make a Digital Stop Watch

 

Good afternoon,all

Recently I am considering making a digital stop watch which can help me exercise. Because I think it's meaning and I'll feel happier than before if I use digital stop watch which made by myself. 

The digital stop watch built around timer IC LM555 and 4-digita counter IC MM74C926 with multiplexed 7-segmetn LED display. Your can look at the following schematic diagram.5.16.4

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.

However,there are some wrongs occurred. Because it’s not counting..it’s always showing 0000 reading but not counting..Meanwhile,plusing the 555 timer is not working with LED but its absolutely okay. 

I want to ask that whether there are someone made such things as me? Can you give me some suggestion?

Thanks a million.

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