timer

Discussion in 'The Projects Forum' started by omar, Feb 19, 2008.

  1. omar

    Thread Starter Member

    Feb 19, 2008
    10
    0
    Hi guys
    I m want to build a timer that runs for 15 minutes and then goes off,
    Any suggestion
    type of timer ?
    Is it easier to use a PIC ?
    thanks
     
  2. spar59

    Active Member

    Aug 4, 2007
    51
    0
    A U6046 or U6047 8 pin dil IC designed for automotive applications such as heated screen timing can produce time delays of 3.7 sec to 20 hours, designed for 12v operation and can switch 300mA. Only problem may be the 1.3mA typical supply current if running from batteries.

    When switched on by an 'on' contact it will switch off by either an 'off' contact or when the time delay expires - needs 3 resistors + 2 capacitors.

    Datasheet available at:-

    http://pdf1.alldatasheet.com/datasheet-pdf/view/90384/TEMIC/U6047B.html

    Steve.
     
  3. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,575
    230
    What starts the timer?
    What does the timer do or control when on.
    What does the timer do or control when off.
    What is your power source.
    Does the timer need to be powered and waiting, or dead, when off?

    The devil's in the details. ;)

    Ken
     
  4. G8NPH

    New Member

    Feb 24, 2008
    3
    0
    PIC's are evil, there not real electronics. use a 555 I.C. in monostable.

    if you change the values of the 2 compovents what go to pins 6 and 7 the time constant will change
     
  5. omar

    Thread Starter Member

    Feb 19, 2008
    10
    0
    This is what i want to achieves
    I want my timer to obstruct the mains power for 15 minutes then go dead.
    After 15 minutes there will be a normal connection between the mains and my module.
    Next time the timer will be on is when the power is on again after a power faillure.

    What starts the timer?
    Mains voltage but i will use a power supply to supply the PIc or 555
    What does the timer do or control when on.
    The timer when on control ..the mains voltage ( it has to hold for 15 minutes then release it )

    Thank you guys for your help ..i hope that extra details that i gave above will help you to have a picture of what i want to achieve .

    What does the timer do or control when off.
    Does the timer need to be powered and waiting, or dead, when off?
    I need my timer to be active only for 15 minutes and wait for the next cycle of mains faillure / power on again

    The devil's in the details.

    Ken
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Sounds like you're attempting to protect an A/C compressor and/or refridgerator/freezer compressor from stalling/overheat when the power is cycled rapidly.

    The former will require monkeying around in the mains panel if the A/C compressor is a permanently installed unit. This is best left up to a licensed electrician.
     
  7. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,575
    230
    Good answers!..now: what is the mains voltage and how much current will the switch need to carry when reconnecting the mains?

    Ken
     
  8. omar

    Thread Starter Member

    Feb 19, 2008
    10
    0
    Thanks again guys,
    My last question is this, my main concern is ..Is it possible to deactivate the timer ..because if i use a timer ( monostable) mode the delay will come back again and again ..it will never stop until a power faillure
    Is it possible to make the timer just go dead after the 15 minutes ...
    I think it s possible to do with A PIC but frankly i don t realy know the circuit may look like if i use a timer
     
  9. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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  10. omar

    Thread Starter Member

    Feb 19, 2008
    10
    0
    Thingmaker 3

    I had a look at the prices of that timer ...god is too expensive
     
  11. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,575
    230
    Omar, there are lot's of Delay-on-Make modules in the $30 to $50 range. Here are some manufacturers the I found while looking for Delay-on-Break modules. These are available through venders like Mouser, Allied, Newark...

    Ken

    http://www.artisancontrols.com/
    http://www.ssac.com/
    http://www.accesscontrolsales.com/
    http://www.airotronics.com/
    http://www.icmcontrols.com/products

    Comment: Most of thes timers handle only about 1A, so if you need to control more current you will also need an electromechanical or solid steate relay.
     
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