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digital timer relay switch, battry powered

Discussion in 'Electronic Design' started by Terry, May 2, 2004.

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  1. Terry

    Terry Guest

    I am looking for a 24 hour event timer that can switch off and on a battry
    operated PIR MURS radio transmiter alarm (Dakota Alert). The pir transmiter
    uses 6- 1.5 volt AA battries for a total of 9VDC power source. When the
    battries are installed it is in sensing 24 hours a day. I use this on a
    const. site and want it to be off during the day and back on at nite, but
    have it done electronically with a selfcontained system. I don,t wand to
    hookup a 120v timer to a 9 vdc converter to switch it. Need a self
    contained, or self powered 9 volt timer that could be set for any time I
    want, to switch every day and save battries.Mabey even be powered by the
    battrie power pack of the murs transmiter. Is there any kind of timer relay
    out there that would work for this?
    Thanks
    Terry
     
  2. Fred Bloggs

    Fred Bloggs Guest

    In your case, the simplest off-the-shelf solution would be an AC line
    timer or photocell switch used to throw battery power onto the alarm
    circuits. Assuming the alarm has an ON/OFF switch- the most unobtrusive
    rig would look like so:
    Please view in a fixed-width font such as Courier.









    +---------------------+
    PLUG | SKT |
    __ | +-------+ PLUG
    | \ | TIMER | ++ | __
    AC ---| -------| | || ++ | | \
    ---| -------| -or- | || || | ---| -------+
    PWR |__ / | | || ++ | ---| -----+ |
    | | ++ | |__ / | |
    | PHOTOCELL +-------+ | |
    | | | |
    ALARM +---------------------+ | |
    +------------+ | |
    | | +----------------------+ | |
    | | | | 18GA | |
    | | | 120VAC RELAY | LINE CORD | |
    | | | +-------------+ | | |
    | | | | | | | |
    | o---------------- o o---------------------+ |
    | ON/OFF | | | \ | | |
    | SW | | | \ coil | | |
    | o---------------- o \ | | |
    | | | | o-----------------------+
    | | | | | |
    | | | +-------------+ |
    | | | |
    | | +------ UTILITY BOX----+
    +------------+
     
  3. Terry

    Terry Guest

    The pir sensor murs radio transmiter dose not contain a on/off switch, but
    is powered when the battries a put in the battry holder.
    Is there such a thing as a 9vdc or low powered 12vdc, 6vdc, photocell switch
    that could be uses as a relay switch in the battry pack line to the pir to
    switch it on/ of dusk to dawn?
    Trying to find prebuilt components, as I just have basic electronics
    knoldege.
    Tks
    Terry
     
  4. Fred Bloggs

    Fred Bloggs Guest

    Yeah it's called a "wire"- put a break in one line of the battery pack
    feed to the alarm and run this through the relay N.O.-COM contacts. If
    you can't comprehend that- then stay away from it.
     
  5. John Fields

    John Fields Guest

    ---
    You'd probably have to build something, and if you wanted to do it
    without a µC it might look something like this:

    +-----+
    +-------+ | _|
    |SET ON |--|A A/B|-----------------------+
    +-------+ | | +----------+ |
    | MUX | | +-----+ | |
    +-------+ | | +--|PR | | +-----+ | +-----+
    |SET OFF|--|B Y|----|D TC|-+-| Q|--+--[C]--|ON |---O
    +-------+ +-----+ | | | ÷2 _| |RELAY|
    |COUNT| | Q|-----[C]--|OFF |---O
    +-------+ | | +-----+ +-----+
    | CLK |-------------|> |
    +-------+ +-----+


    Using CMOS 4000 family parts, (so you could use the 9V XMTR supply) a
    32768 Hz clock, and 1 minute timing resolution, you'd need a 4060 and
    a 40103 for the clock generator, eight 4-bit BCD switches and 14
    pullup or pulldown resistors to set the ON time and OFF times, four
    40257s for the 2:1 mux, two 40102s for counters, half of the 4013 for
    the ÷2, and a couple of differentiators (shown as [C]) to drive the
    relay, a single coil polarized latching type so it would only draw
    coil current during the ÷2's transitions, and a few chips for glue
    logic, which comes to about 12 chips.

    The up side is that the only thing drawing any appreciable dynamic
    current would be the 4060, and that would be microamps, so the timer
    load on the 9V battery would be negligible.

    But Ooops... I forgot...

    Once the minutes counter times out the first time it has to be preset
    to 60 thereafter to count off hours, so that's another couple of
    muxers, which brings the chip count up to about 14.

    Hmm... a µC is starting to sound pretty attractive!
     
  6. John Fields

    John Fields Guest

    ---
    Aaarghhh...

    First it's you want to be able to set the ON and OFF time to any times
    you want and now it's all you really want is a dusk and dawn sensor?

    If you don't know what you're talking about, take it over to
    sci.electronics.basic where it's OK to waste people's time.
     
  7. Fred Bloggs

    Fred Bloggs Guest

    The cheapest and simplest thing I can think of, short of finding an
    actual product, is to grab some experimental solar cells and a 3V relay
    from Radio Shack, and hook this up so that sun goes down, solar cell
    output drops , relay drops out and throws power to your alarm. Like so:
    Please view in a fixed-width font such as Courier.
    ..
    ..
    .. relay 3V coil +------+
    .. +------------------+ | |
    .. | | | +---+
    .. | o -|---+ | | stack
    .. | NC NO | | +---+
    .. +-----|- o o / | | solar
    .. | | coil| +---+
    .. | | / | | | cells
    .. | +--|---- o \ | +---+
    .. | | | | | | for 3V
    .. | | | COM o -|----+ .
    .. | | | | | +---+
    .. | | +------------------+ | | |
    .. | | | +---+
    .. | | | |
    .. | | +-----+
    .. | |
    .. | |
    .. | +---------------------------------------+
    .. +--------------------------------------+ |
    .. | |
    .. | |
    .. +-------------------------------------------------+ | |
    .. | ------- + ------- + ------- + | | |
    .. | | | | | | | | | |
    .. | (-)---| ] | ] | ] --+ | | |
    .. | | | | | | | | | | |
    .. | ------- ------- ------- +-|-+ |
    .. | alarm | |
    .. | input +-|-----+
    .. | + ------- + ------- + ------- | |
    .. | | | | | | | | | / \
    .. | (+)- [ | [ | [ | --+ | |
    .. | | | | | | | | |
    .. | ------- ------- ------- | |
    .. +-------------------------------------------------+ |
    .. BATTERY CRADLE |
    .. |
    .. BREAK CRADLE
    .. LINK HERE
    ..
     
  8. Fred Bloggs

    Fred Bloggs Guest

    You should be able to find one of those 12V solar car battery chargers
    that plugs into the cigarette lighter- then get yourself a screw base
    12VDC relay, and possibly an ON/OFF toggle switch for override, modify
    the alarm battery cradle, and you're done:
    Please view in a fixed-width font such as Courier.

    ..
    .. 12V SPDT or DPDT
    ..
    .. RELAY +------+
    .. +------------------+ | |
    .. | | | +---+
    .. | o -|---+ | |
    .. | NC NO | | | |
    .. +-----|- o o / | | |
    .. | | coil|
    .. | | / | 12V PANEL
    .. | +--|---- o \ |
    .. | | | | | | |
    .. | | | COM o -|----+ | . |
    .. | | | | | | |
    .. | | +------------------+ | | |
    .. | | | +---+
    .. | | | |
    .. | | +-----+
    .. | |
    .. | +---------------------------------------+
    .. +--------------------------------------+ |
    .. | |
    .. | |
    .. +---|---|---+
    .. OVER-RIDE------> ON/OFF | | | |
    .. ( TURN ON TO) SWITCH | o o |
    .. ( OVERRIDE ) | | | |
    .. +---|---|---+
    .. | |
    .. +-------------------------------------------------+ | |
    .. | ------- + ------- + ------- + | | |
    .. | | | | | | | | | |
    .. | (-)---| ] | ] | ] --+ | | |
    .. | | | | | | | | | | |
    .. | ------- ------- ------- +-|-+ |
    .. | alarm | |
    .. | input +-|-----+
    .. | + ------- + ------- + ------- | |
    .. | | | | | | | | | / \
    .. | (+)- [ | [ | [ | --+ | |
    .. | | | | | | | | |
    .. | ------- ------- ------- | |
    .. +-------------------------------------------------+ |
    .. BATTERY CRADLE |
    .. |
    .. BREAK CRADLE
    .. LINK HERE
    ..
    ..
    ..
    ..
    ..
     
  9. Fred Bloggs

    Fred Bloggs Guest

    This is what I'm talking about- whatever you find just match it with
    same relay voltage:
    http://www.batteries.com/productpro...no=&groupname=Solar+Chargers&groupcode=CHARGE
     
  10. Colubris

    Colubris Guest

    Hi Terry,
    How about hacking a "digital appliance timer". They're meant to switch
    AC loads, but many varieties can also be used to switch low voltage
    loads - or can be modified as needed.
    Rat Shack sells some, and Intermatic has some useful models too.

    Arch
     
  11. Joerg

    Joerg Guest

    Hi Terry,

    Here is a simple solution: Use an analog quartz alarm clock (used to be about $7
    at Longs Drugs). Open the contact switch wiring. Hook up a long CMOS counter
    which can be done in one single chip. Look up the MC14521 which I believe has
    the gates for the oscillator in there and includes the long counter. Power
    consumption is minimal and the voltage is non-critical, 9V is just fine. Then
    configure it to run from contact closure which is set to end of workday to
    whenever work resumes.

    You have to make sure the clock can tolerate this surgery and that it's all
    reliable.

    Even simpler: Then there are the battery operated irrigation valves. About $50
    or so at Home Depot. If you disable the valve part and figure out to connect to
    the innards, some can be programmed to "water" from, say, 6:00pm to 7:00am or
    whatever you program in there. These have the advantage that you can reprogram
    them via push buttons when, for example, an extra shift is scheduled one day.
    Just get one that's easy to program and can run this long.

    Regards, Joerg
     
  12. Joerg

    Joerg Guest

    Terry, just one addendum: Some of those irrigation timers have an open and close
    function so they don't eat batteries while holding a valve coil, which means
    that you'd need a simple set-reset flip flop at the output. But that can be done
    with a couple transistors and four resistors.

    Regards, Joerg
     

  13. Also, make sure you can water that long before you buy. The two I've owned
    had a maximum of 4 hours watering as I recall. A safety feature, they say.

    Regards,
    John
     
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