stay on relay

Discussion in 'The Projects Forum' started by keepitbrief, Aug 20, 2009.

  1. keepitbrief

    Thread Starter New Member

    Aug 20, 2009
    6
    0
    hi can anyone help i need a 12v relay that comes on with signal as normal relay dose, but after signal drops the relay remains closed for approx 10 seconds ?
     
  2. S_lannan

    Active Member

    Jun 20, 2007
    247
    2
    sounds like a job for a 555 timer. are you familiar with those?
     
  3. keepitbrief

    Thread Starter New Member

    Aug 20, 2009
    6
    0
    Thanks, s lannan ill look into it , not familiar with 555 im new to eletronics.
     
  4. n9352527

    AAC Fanatic!

    Oct 14, 2005
    1,198
    4
    Check out time delay relay. Much easier to work with, and ready to use.
     
  5. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    2 ways -

    The hard way - Get a 555 timer, wire it in monostable mode to get very accurate timing.

    The easier way, if you dont need it to be precise, add a 4700uF (or maybe more) capacitor across the relay terminals. Sometimes you can make it work with a 1000uF and a transistor. Timing will need to be experimented with to make it accurate.
     
  6. daviddeakin

    Active Member

    Aug 6, 2009
    207
    27
    Here's a possibility. The cap is charged quickly when the input trigger is applied, and so the relay operates very fast, but C1 cannot discharge quickly because of the diode so the relay should stay closed for a few seconds. I have guessed at part values, R1 would probably need to be adjusted to get the right timing.
     
  7. keepitbrief

    Thread Starter New Member

    Aug 20, 2009
    6
    0
    thacks jj will try it out talked with a friend about this, but did not know whitch capacitor
    regards
     
  8. keepitbrief

    Thread Starter New Member

    Aug 20, 2009
    6
    0
    cheers daviddeakin will have play with it
    regards
     
  9. keepitbrief

    Thread Starter New Member

    Aug 20, 2009
    6
    0
    guys would a internal car lamp delay relay do what i need ????just been looking a stuff and had a u,recka moment ???
     
  10. Steve C

    Active Member

    Nov 29, 2008
    86
    0
    How much innacuracy can you stand to have in the circuit? Do you need BASICALLY 10 seconds, and it's cool if you are off by a ton? 10 is the ballpark?

    [​IMG]

    bam, easy.
     
  11. keepitbrief

    Thread Starter New Member

    Aug 20, 2009
    6
    0
    thancks steve will give that a go, the 10 seconds is a ballpark figer but any were from 8 to 20 seconds would be good , is the part number for the trasistor a comon numer did a search on maplins did not find it!
    thancks again
     
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