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some sort of resettable switch

Discussion in 'General Electronics Discussion' started by queensland_jack, May 6, 2012.

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  1. queensland_jack

    queensland_jack

    4
    0
    May 5, 2012
    Hi,, i wonder if anyone can advise how solve my problem...
    I have a Omron timer H3CA-8,, my problem is,, i live in rural area, and the mains power is not very stable or reliable..well what happens is when there in a power interruption,,, the timer atomatically restarts..
    so for example,,, it it was set to turn off the item after 1 hour.. then,, if in 30 minutes, there is a power disruption, even if just for a momnet.. then it will start again for another 1 hour..
    so obviously that is no good if yu want a definate time to run something..
    The same thing if the timer has finished it's timing cycle, and there is a power disruption, then it stats again...
    i was thinking that maybe there is a power detection curcuit , that i could use,that will stay switched off and have to be manually reset after a power disruption..?
    or some switch that maybe i can buy that would do the job..
    or even, wud it be possible to use some big capacitor to keep the power maintained to the timer?
    Any ideas would be hight appreciated............. thanks..
     
  2. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    Well depending on total power requirements you might be able to get by with a computer battery backup even a small one if you isolated the timers supply and only draw that from the battery backup... Small glitches and even small down times will be smoothed over...
     
  3. queensland_jack

    queensland_jack

    4
    0
    May 5, 2012
    Hi,, yes thanks,, thats an idea... i am not sure how much a small power back-up would be ?,,
    The power requirment is only very small,, i think it says in specifications:10VA,1W,,, the power supply would only has to run the timing switch,,,the switch runs external relays..
     
  4. CocaCola

    CocaCola

    3,635
    5
    Apr 7, 2012
    If you are only powering the timer, you can get by with one of the cheaper $50 or so baby backup units, you will be able to even coast over many minutes of no power or intermittent power without issue...
     
  5. queensland_jack

    queensland_jack

    4
    0
    May 5, 2012
    ah , ok ,, thanks...
    Would the power back last for say 24 hours or more?
     
  6. duke37

    duke37

    5,364
    772
    Jan 9, 2011
    Electric motor contactors - those with a red and green button - will stay off if the power is interupted. This is probably overkill for your purpose
    You can make a small one with a latching relay, here the problem would be to obtain or make a safe enclosure.
     
  7. queensland_jack

    queensland_jack

    4
    0
    May 5, 2012
    Yes,i thought of the motor contactor,, but as you said,, a bit of an over-kill,,,
    a cheap latching relay would be the go..!!
    No problem with me making a safe enclosure,, thats one of my hobbies...
    i been making power supplys for 35 years,,,,
    Does anyone have a schematic curcuit for to make a latching relay?
     
  8. duke37

    duke37

    5,364
    772
    Jan 9, 2011
    Here is the idea, you can take output from a second set of contacts or from the relay coil supply.
     

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