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Timer

Discussion in 'Electronic Repair' started by LSMFT, Oct 19, 2010.

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  1. LSMFT

    LSMFT Guest

    I'm trying to find a timer to do what I want. Descriptions on the
    internet are sadly inadaquate.
    I want a timer that if it has input, say from a thermostat, to come on
    for a set time (2 to 5 minutes) and cut off. And I want it to do this
    every 15 minutes to 2 hours. What kind of timer do I need.
    I don't mind wiring an octal socket it they come that way.
     
  2. LSMFT

    LSMFT Guest

    I'm working with 120 volts. The gate is thermostat closed or 120
    applied. When closed, start 2 to 5 minute timer. If set for 3 minutes,
    keeps contacts closed for 3 minutes as along as the gate is closed.
    Otherwise do nothing or drop out if gates opens.
    If gate is still closed do it again in 30 minutes to 2 hours, otherwise
    do nothing.
     
  3. LSMFT

    LSMFT Guest

    The load is a circulator 120 VAC.
     
  4. LSMFT

    LSMFT Guest

    Can a programmable thermostat do this? I thought not.
     
  5. shrtrnd

    shrtrnd

    3,827
    520
    Jan 15, 2010
    Use a TDR (Time Delay Relay),
    They are also made in an octal base package.
    You select a fixed time interval from manufacturer, or a variable adjustment in say 0 to 5 minutes.
    Check Newark Electronics, or Allied Electronics for starters.
     
  6. LSMFT

    LSMFT Guest

    How about two re-triggerable one shots with variable delay shutoff in
    series.
     
  7. Art Todesco

    Art Todesco Guest

    If you're into building it yourself, here's a link to a schematic:
    http://www.zen22142.zen.co.uk/Circuits/Timing/ivt.htm
     
  8. LSMFT

    LSMFT Guest

    I would have no problem building it. That's what my trade used to be.
     
  9. Art Todesco

    Art Todesco Guest

    You might be able to do it with a single 555, but this one was already
    designed and was easily adjustable for each part of the cycle.
     
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