Minute clock timer alarm for one second

Discussion in 'General Electronics Chat' started by Nature Calls, May 12, 2010.

  1. Nature Calls

    Thread Starter New Member

    May 12, 2010
    1
    0
    Hello,

    I'm trying to figure out how to modify a electronic light timer to pulse for just a second or so. How can I "hack" a regular hardware store light control timer to turn off/on for only seconds rather than minutes?

    I want to be able to set the timer to turn on twice during the day, but only long enough to trigger a relay very briefly. Fore instance I want to trigger a solenoid for just a second. Is there a way I can use an ordinary light timer to turn on and off in a second?

    Normally, I can set a light timer to turn on at a certain minute then off at the next minute. Is there a way to turn it off sooner or to "reroute" the power away from a relay so that it doesn't hold it on for a whole minute?

    Thank you,
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    Not the standard analog ones.

    With the digital ones, you may be able to swap the crystal out for one 60 times faster, that would make a minute a second, but then you would have 24 minute days.

    Is this an important task? If so, I would look for a digital timer that you can set to the second. They are available but expensive.

    The next thing I would suggest is to use a 555 one shot to fire the relay for how ever long you want the relay energized for. You can use your standard timer your talking about to trigger the 555. It will only fire on the rising edge. So when the timer hits 3:06am, the timer turns on for a minute, but the 555 only triggers power to the relay for however long you have the 555 set for. Then it waits for the next trigger. That can happen at 11:38pm. Again the rising pulse of the store timer will trigger the 555 to energize the relay for the short time.
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    2,536
    Or you could put a simple monostable circuit that is triggered off the timer. The monostable would output the required 1 - 2 seconds you are asking for.
     
  4. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,575
    230
    Since you have (?) a timer and would have needed a low voltage DC supply for any IC monostable circuit, you only need three more components. The timer is set to trip ON for the minimum time. The ON-time for the monostable is determined by the coil resistance, the value of the capacitor, and the drop-out voltage of the relay.

    Ken
     
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