need help with stopwatch switch

Discussion in 'The Projects Forum' started by liangjx, Mar 24, 2009.

  1. liangjx

    Thread Starter New Member

    Mar 5, 2009
    1
    0
    Hi guys,i'm a first year Chinese student in UK.

    i'm recently working on my digital project which i have to make a stopwatch count from 0 to 999sec and i got it entirely working. However, i don't know how to make a switches to control the operation of the circuit like start,stop and reset.

    I found this great website on google and basically i need help. thx for reading my message and nice to meet you all:)
     
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,694
    904
    Many years ago, I needed to do a similar thing. I started with some very inexpensive stopwatches from WalMart or similar. On those watches, the various functions were each inititiated by grounding the appropriate pin. So, I just ran a fine wire from that pin to this circuit. The stopwatch button could be left in place.

    [​IMG]

    So far as I know, none of the values are critical. That was the very first circuit I designed/built after more than a 30-year lapse. I suspect some of the values could be changed to make it work better. For example, you might want to increase the collector resistor.

    John
     
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