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Discussion in 'Misc Electronics' started by Afterburner, Dec 16, 2003.

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  1. Afterburner

    Afterburner Guest

    To start with I purchased a window air
    conditioner and installed it in a wall. It is very
    difficult to remove and work on. It is important that
    the a/c runs two hours a day to reduce humidity.The
    previous a/c worked with an on/off switch. As a result
    I could connect it to a mechanical timer and it would
    turn on and off at certain times.
    The new a/c has a key pad and a remote, but to my
    dismay when I hooked it up to the timer it would not
    start; a button on the keypad had to be physically
    pushed to turn it on, or turned on by a TV type remote.
    I found that I could wire into the remote and close
    the remote circuit and the IR would trigger the a/c to
    operate. I used a micro switch on a mechanical timer
    to close the circuit and turn the a/c on and off.
    This system works fine, except if the power goes off,
    the timer can go out of sync and run for 22 hours day after day.
    Long route to get to the point:
    I need a circuit (or conversion) that will close the remote's circuit twice
    a day that is battery operated (C cell or D cell). I was hoping someone
    would have a diagram and/or a suggest on the conversion of a timer.
  2. Ken Taylor

    Ken Taylor Guest

    Make/model of aircon?

  3. afterburner

    afterburner Guest

    Model a/c is Maytag 12000 btu, window installation with heat. Model
    number is in Florida,;I'm in Houston. Unit cost was $500.00, Home
  4. afterburner

    afterburner Guest

    This sounds like a "brillant" solution, but I have never heard of a
    timer on a programable remote. Give me a clue where to look for this
    item. TUVM Afterburner
  5. afterburner

    afterburner Guest

    Thought I answered this question, but it didn't get on line: It's a
    Maytag 12000 Btu with heater, costs $500 at Home Depot. Serial number
    and unit is in Florida; I'm in Houston.
  6. afterburner

    afterburner Guest

    Tried to answer you by email, but no luck.
    When the A/C shuts down after the cycle it will not turn on again
    unless the start button on the pad is pushed or the remote is
    activated. I activate the remote with an AC electrical timer that
    closes a micro switch, mecanically, This switch closes the start
    circuit on the remote and the remote turns on the A/C. In about two
    hours the timer trips the microswitch and turns the A/C off. The
    microswitch is bolted to the timer and the little green and red nubs
    close and open the microswitch as the timer rotates. Not rocket
    science just a $5.00 timer and a $1.00 microswitch. Works fine except
    if the power goes out, it goes out of sync.
    Are you telling me that rcu-810A comes on automatically every day and
    would start and stop the Air conditioner functioning similar to the
    the electromechanical setup I have now? I tuvm for your comments.
  7. John Fields

    John Fields Guest

    Cute problem.

    Sounds like if the AC mains go off while the AC is on for its 2 hour
    dehumidifying run and then the mains come back on before the remote
    issues the OFF pulse, the AC won't come back on immediately when the
    mains come back up, but will wait until it gets the OFF pulse from the
    rempte, which it will interpret as an ON pulse and then turn on and run
    until it gets the next pulse 22 hours later, go off for two hours and
    then go back on for 22, no?

    As I see it, there are basically two routes you can take to arrive at a
    solution, the first being to put some smarts into the circuitry that's
    running the remote, and the second being to put some extra smarts into
    the AC itself. Since the AC is already wired to the mains and there
    needs to be some awareness of what the mains are doing/have done, I'd
    be tempted to start there insted of having to make the circuitry driving
    the remote mains-aware. But since you say the AC is a beast to work
    on, rigging the remote may well be the best way to go.

    First, since you want something to keep time independently of what the
    mains is doing you'll need a (crystal-controlled?) timer that runs on
    batteries or runs off the mains and switches over to batteries in case
    of mains failure. If you use the switchover scheme you can make the
    batteries last for a _long_ time.

    There are only five possible combinations of mains ON/OFF occurrences
    interacting with timer ON/OFF siganls, only two of which result in
    permanent ON/OFF time reversals:

    First, normal operation:

    _ _ _ _
    TIMER ____|1|_____|2|__________|1|_____|2|________
    | | | |
    22Hr -->|<-2Hr->|<---22Hr--->|<-2Hr->|<---22Hr..
    ______ ______
    AC _____| ON |____OFF_____| ON |_____OFF____

    Second, an ON/OFF time reversal occurs when a mains failure and
    subsequent recovery brackets the timer's ON pulse:

    ___ ____________________________________
    MAINS |___|
    _ _ _ _
    TIMER ____|1|_____|2|__________|1|_____|2|________
    | | | |
    22Hr -->|<-2Hr->|<---22Hr--->|<-2Hr->|<---22Hr..
    _____ ____________ __________
    AC __X__|__OFF__| ON |__OFF__| ON

    Third, an ON/OFF time reversal occurs when a mains failure occurs and
    subsequent recovery occurs between the timer's ON and OFF pulses:

    ________ _________________________________
    MAINS |_|
    _ _ _ _
    TIMER ____|1|_____|2|__________|1|_____|2|________
    | | | |
    22Hr -->|<-2Hr->|<---22Hr--->|<-2Hr->|<---22Hr..
    _________ ____________ __________
    AC __X__|_X_|___| ON |__OFF__| ON

    Fourth, when a mains failure and subsequent recovery brackets the
    timer's OFF pulse, an ON/OFF time reversal doesn't occur.

    _________ __________________________
    MAINS |_______|
    _ _ _ _
    TIMER ____|1|_____|2|__________|1|_____|2|________
    | | | |
    22Hr -->|<-2Hr->|<---22Hr--->|<-2Hr->|<---22Hr..
    _________ _______
    AC ___X_|_X_|______OFF_______| ON |___OFF____

    Fifth, when a mains failure and subsequent recovery falls between the
    timer's ON and OFF pulses, an ON/OFF time reversal doesn't occur.

    ________________ ____________________
    MAINS |______|
    _ _ _ _
    TIMER ____|1|_____|2|__________|1|_____|2|________
    | | | |
    22Hr -->|<-2Hr->|<---22Hr--->|<-2Hr->|<---22Hr..
    _________________ _______
    AC __X__|__X____|_X_|__OFF___| ON |___OFF____

    Since we need only concern ourselves with the mains failures which cause
    ON/OFF time reversals, we need only concern ourselves with the instance
    where the mains failure and recovery brackets the timer's ON pulse and
    with the instance when the mains failure and recovery occurs between the
    timer's ON and OFF pulses.

    With that in mind, we should be able to devise a strategy which will
    keep the OFF pulse from turning ON the AC. Examining the timing
    diagrams above makes it evident that the only time we'll run into
    trouble is when a mains failure occurs and its recovery is followed by a
    timer OFF pulse, so if we can suppress that next OFF pulse and allow the
    ON pulse following that to turn on the AC and enable the following OFF
    pulse(s), that ought to work.

    IMO, the easiest way to do the whole thing would be to find out what the
    remote was sending as an ON/OFF signal, then use a µC to generate that
    sequence and do everything else as well. To do it all in hardware and
    get a contact closure to do the switching at the remote is pretty
    straightforward, albeit somewhat time-consuming, but it might be fun and
    I can help you with circuit design and schematics if you like...
  8. The microchip website (manufacturers of PIC) has a technote on controlling
    IR remote controls. IIRC, it actually records the IR signal in eeprom, and
    plays it back when activated. Not a bad scheme, actually. Otherwise, you are
    stuck with analyzing the remote control protocol, which isn't too hard, its
    just a matter of determining which protocol it uses.

    Also, there is a 'remote control' lamp controller design around that does
    the same thing (records, then replays the signal) using a PIC.
  9. afterburner

    afterburner Guest

    John, thank you so much for your imput. Your identification of the
    problum is "spot on!" The analysis does credit to your deductive
    skill. I have also done some analysis in the area of failure and
    determind the probability of failure at 8 per cent. I agree that the
    simplist way to solve the problem is a shunt on the on/off switch and
    a mechanical timer. The A/C is , as you say a beast to move, and
    requires three people to move because of its high location. Right now
    I am on hold, because I have located a timing devise that runs on two
    "C" batteries and turns water on to a garden hose and shuts it down at
    a specific interval. The inner workings are a small motor, gears, and
    a cut off switch. All this is controled by some regulating chip and
    other electronic parts. Problem is the one I have is defective and the
    manufacturer no longer makes a Nelson 5700 control valve. I planned to
    use the output to the motor to close a relay that closes the circuit
    and fires the remote. simple and easy. The Nelson company may have the
    parts, if they do: fine! If they don't I will look for another devise
    that operates similarly on battery power.
    For now I'm going to consentrate on Christmas and New Years. If I get
    the job done with this type of arrangement I will let all know, same
    if I don't!

    Best to all of you on this New Year and a very grateful thanks!

  10. CWatters

    CWatters Guest

    What happens if you hold that button down when the unit is powered up by the
    timer? eg could you just fix that button down all the time?
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