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My Stopwatch circuit won't goes up after 9 minute

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dennyrizram

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I have a project to create a stopwatch using some cmos ic. i use cd4060 and cd4027 as my 1 hertz clock and using 4 cd4026 as my counter and decoder to my 7 segment display. My circuit supposed to have 99 minute count maximum. But in my case now after it reaching 9 minute 59 second, they all back to zero. Can someone tell me what is wrong with my circuit?
 

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Les Jones

Well-Known Member
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Check that carry out (Pin 5) on U5 goes from low to high when the display shows 5 minutes and zero seconds and it goes back to low when the display goes from 9 minutes 59 seconds to zero. (Which should be 10 minutes.) Also check this signal at the clock input of U6 (Pin 1). When you have done this report the results.

Les.
 

dennyrizram

New Member
Check that carry out (Pin 5) on U5 goes from low to high when the display shows 5 minutes and zero seconds and it goes back to low when the display goes from 9 minutes 59 seconds to zero. (Which should be 10 minutes.) Also check this signal at the clock input of U6 (Pin 1). When you have done this report the results.

Les.
Okay i did what you instructed Les. The carryout from U5 apparently always high even when the minute displaying 5-9. The input clock from U6 has the same condition, always high. Then i notice that in my circuit PCB, the conductor track for pin 3 (DC Input) of U6 was adjacent with conductor track for carryout of U5 that somehow making them short circuit. So after i clear some conductor track between them my circuit is working now.
Thanks for pointing out how the CD4026 work, i've never know that the 4026 giving high to carry out when it count 0-5, and give low when it count 5-0.
 
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