Wireless doorbell switch

Discussion in 'Electronic Basics' started by BoB, May 13, 2005.

  1. BoB

    BoB Guest

    Hi

    Is it possible to convert the output of a wireless

    Doorbell to power a small relay or switch?

    Thanks in advance

    Bob
    BoB, May 13, 2005
    #1
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  2. One day BoB got dressed and committed to text

    > Hi
    >
    > Is it possible to convert the output of a wireless
    >
    > Doorbell to power a small relay or switch?
    >
    > Thanks in advance
    >
    > Bob


    If you have to ask, it might be beyond your capabilities but it should be a
    relatively simple task to divert the output of the reciever to control relay
    or whatever.
    Thats a pretty broad question BTW

    --
    Regards ..... Rheilly Phoull
    Rheilly Phoull, May 14, 2005
    #2
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  3. Terry Pinnell, May 14, 2005
    #3
  4. BoB

    BoB Guest

    "Terry Pinnell" <> wrote in message
    news:...
    > "BoB" <> wrote:
    >
    > >Hi
    > >
    > >Is it possible to convert the output of a wireless
    > >
    > >Doorbell to power a small relay or switch?
    > >
    > >Thanks in advance
    > >
    > >Bob
    > >

    >
    > Here are examples of two simple circuits I've used to do that:
    > http://www.terrypin.dial.pipex.com/Images/Doorbell-Interfaces.gif
    >

    Thanks for that Terry, I am building a set of starting lights
    for mini moto racing, im using a 555 and a 4017 to give
    the "Christmas tree" effect. I just need a way of starting the count from
    the start line, so I figured a wireless doorbell would be a cheap
    option, Wilkos sell them for under £5.
    Im planning to hook the output up to the reset pin of the 4017 to
    start the sequence. Maybe leave the first couple of outputs unused
    to allow for any false starts due to the chime pattern of the doorbell.
    Hope Im making sense now, I realise my first question was a little vague.

    Bob
    BoB, May 14, 2005
    #4
  5. BoB

    Rich Grise Guest

    On Sat, 14 May 2005 09:24:57 +0100, BoB wrote:

    >
    > "Terry Pinnell" <> wrote in message
    > news:...
    >> "BoB" <> wrote:
    >>
    >> >Hi
    >> >
    >> >Is it possible to convert the output of a wireless
    >> >
    >> >Doorbell to power a small relay or switch?
    >> >
    >> >Thanks in advance
    >> >
    >> >Bob
    >> >

    >>
    >> Here are examples of two simple circuits I've used to do that:
    >> http://www.terrypin.dial.pipex.com/Images/Doorbell-Interfaces.gif
    >>

    > Thanks for that Terry, I am building a set of starting lights
    > for mini moto racing, im using a 555 and a 4017 to give
    > the "Christmas tree" effect. I just need a way of starting the count from
    > the start line, so I figured a wireless doorbell would be a cheap
    > option, Wilkos sell them for under £5.
    > Im planning to hook the output up to the reset pin of the 4017 to
    > start the sequence. Maybe leave the first couple of outputs unused
    > to allow for any false starts due to the chime pattern of the doorbell.
    > Hope Im making sense now, I realise my first question was a little vague.


    The question wasn't vague to me, but the only answer I have is "It depends
    on what the doorbell receiver's output is." For example, if it has a
    physical, electromechanical chime, with visible wires to the receiver,
    then it's probably a DC signal that'd be trivial to hook to a relay.
    (You'd just replace the chime with the relay coil). But if the doorbell
    has its own oscillator and speaker, then you would need to pick up the
    signal off the speaker leads, but then you'd have to do some "signal
    conditioning", and what kind of conditioning you do depends on what kind
    of speaker it is, what the sounds are that it's outputting, and so on.

    I picked up the signal to the little piezo beeper in an alarm clock
    once, but it was just a pulse train. I used a capacitor to "sense"
    the pulse train and trigger a one-shot (monostable multivibrator),
    that would trigger on the first pulse, and hold _its_ output active
    for A) as long as the alarm was alarming, since it was a retriggerable
    one-shot, plus B) the time-out of the one- shot after the last pulse.

    Hope this is a better answer than "Sorry, we need more information." :)

    Good Luck!
    Rich
    Rich Grise, May 14, 2005
    #5
  6. "BoB" <> wrote:

    >
    >"Terry Pinnell" <> wrote in message
    >news:...
    >> "BoB" <> wrote:
    >>
    >> >Hi
    >> >
    >> >Is it possible to convert the output of a wireless
    >> >
    >> >Doorbell to power a small relay or switch?
    >> >
    >> >Thanks in advance
    >> >
    >> >Bob
    >> >

    >>
    >> Here are examples of two simple circuits I've used to do that:
    >> http://www.terrypin.dial.pipex.com/Images/Doorbell-Interfaces.gif
    >>

    >Thanks for that Terry, I am building a set of starting lights
    >for mini moto racing, im using a 555 and a 4017 to give
    >the "Christmas tree" effect. I just need a way of starting the count from
    >the start line, so I figured a wireless doorbell would be a cheap
    >option, Wilkos sell them for under £5.
    >Im planning to hook the output up to the reset pin of the 4017 to
    >start the sequence. Maybe leave the first couple of outputs unused
    >to allow for any false starts due to the chime pattern of the doorbell.
    >Hope Im making sense now, I realise my first question was a little vague.


    OK, understood. It should be straightforward to get a +ve going signal
    for the 4017 reset pin by adapting one of those two methods I
    illustrated. Details depend on what doorbell you have, as that will
    determine the power supply arrangements and of course the duration of
    its original chime signal. For example, if it's of the second type,
    simply inverting the 4s output (with say a transistor or a spare logic
    gate) would be sufficient, providing your Christmas Tree cycle time
    was well over 4s, so that the long reset wouldn't matter.

    --
    Terry Pinnell
    Hobbyist, West Sussex, UK
    Terry Pinnell, May 16, 2005
    #6
  7. BoB

    Chris Guest

    BoB wrote:
    > Thanks for that Terry, I am building a set of starting lights
    > for mini moto racing, im using a 555 and a 4017 to give
    > the "Christmas tree" effect. I just need a way of starting the count

    from
    > the start line, so I figured a wireless doorbell would be a cheap
    > option, Wilkos sell them for under £5.
    > Im planning to hook the output up to the reset pin of the 4017 to
    > start the sequence. Maybe leave the first couple of outputs unused
    > to allow for any false starts due to the chime pattern of the

    doorbell.
    > Hope Im making sense now, I realise my first question was a little

    vague.
    >
    > Bob


    Hi, Bob. There have been a few questions recently about using these
    cheapie wireless doorbells for remote control. I happened to have one
    around, so I took it apart to see what's inside. And if yours is like
    mine, you can do your circuit fairly easily.

    I've got a "Dimango by Lamson Home Products", Model 3110R. The
    receiver is powered by 2 AA batteries, which gives 3VDC. There is a
    coil and some discretes and transistors for the analog front end, with
    a CMOS 4069 in the front end, too. This goes to a C.O.B. (Chip on
    Board) PIC or other cheapie microcontroller (uC) mounted on a separate
    small circuit board soldered to the main board. As far as I can see,
    there's only one output from the uC -- the one going to the dinger.
    That's a small 8 ohm 1/4 watt speaker.

    When you're looking at interface, many times you don't have to have
    Yoda-like understanding of the entire circuit -- just the part that
    you're working with. I tracked down the circuit board traces and came
    up with this for the output (view in fixed font or Notepad):

    ` VCC
    ` +
    ` |
    ` |
    ` | __ /|
    ` '--| | |
    ` .--|__| |
    ` | \|
    ` | 8 ohm
    ` COB ___ |/ 1/4 watt
    ` o-----|___|--|
    ` Output R |>
    ` |
    ` |
    ` ===
    ` GND
    (created by AACircuit v1.28.5 beta 02/06/05 www.tech-chat.de)

    Well, that's something we can use. You know that with a 3V power
    source, you'll probably get at least 2V square wave across the speaker
    when the doorbell output transistor is on (transistor saturation and/or
    battery voltage drop will keep the transistor from going fully on).
    Now we're getting somewhere. We know it won't hurt the anything to
    replace the speaker with a 1K resistive load like it shows in Mr.
    Pinnell's link (you don't need the bell sound, anyway), and we can use
    that voltage drop across the resistor to interface to the digital stuff
    with another transistor:


    VCC
    +
    |
    .-.
    | |
    1K| |
    '-'
    |
    |
    o--->
    | Logic Level Signal
    |
    |
    |
    |
    ___ |/ 2N
    o----o------|___|--| 3904
    From | 3.3K |>
    Door .-. |
    Bell | | |
    Spkr | |1K |
    Drive '-' |
    | |
    o----o ===
    | GND
    ===
    GND
    (created by AACircuit v1.28.5 beta 02/06/05 www.tech-chat.de)

    At this point, if you can program a PIC, you're almost home. You can
    ignore the several seconds of pulses which follow the start of the
    doorbell ring, and start your sequence. Since you can get 20mA out of
    a single output pin as long as you don't exceed 40mA per port, you can
    drive the LEDs directly (with a current-limiting resistor), with one
    input pin and 6 output LEDs (5 amber, one green). If you wanted to be
    really crafty, you could just replace the speaker with a 100 ohm
    resistor, use the two battery power supply for the PIC and forget the
    level-shifting transistor.

    But your post suggests you want to do this with 555s and a 4017, which
    leads me to believe you don't have that capability. Doing this with
    digital logic ICs, you're going to have some issues. The biggest one
    is that the transistor will be turning the speaker on and off for
    several seconds. It's a square wave, right? You want to have a single
    pulse which starts when you press the button. So, you can use the
    transistor pulse to trigger a 555 to a single pulse longer than the
    time the doorbell is sounding (let's be generous and say 10 seconds).


    VCC VCC VCC VCC
    + + + +
    | | | |
    .-. .-. | |
    | | | |150K | |
    1K| | | | | |
    '-' '-' | |
    | | .---o-----o---.
    | | | 8 4 |
    o----------)----o 2 |
    | | | | A
    | | | 3 o----->
    | o----o 6 |
    | | | LM555 |
    | | | |
    ___ |/ 2N o----o 7 |
    o----o------|___|--| 3904 +| | |
    From | 3.3K |> --- | |
    Door .-. | 100uF --- | 1 5 |
    Bell | | | | '---o-----o---'
    Spkr | |1K | | |
    Drive '-' | | |
    | | | |
    o----o === === ===
    | GND GND GND
    ===
    GND
    (created by AACircuit v1.28.5 beta 02/06/05 www.tech-chat.de)

    Now you have to look at some details. Your 555 has a positive-going
    pulse when it's turned on, but the 4017 requires an active low (the
    reset input to the 4017 is valid for a "1" input). So, you can use
    another transistor to invert the logic. You need another 555 to count
    down the Christmas Tree, and you can use the terminal count ("6" below)
    to put CLKEN (clock enable) high, which inhibits counting. That will
    mean the green LED will stay on until the first 555 goes off. Here's
    The rest of the circuit (again, view in fixed font or Notepad):


    VCC
    +
    A >---------------o--------. |
    | | .-.
    VCC | | | |4.7K
    + | | | |
    | | .-. '-'
    .-. VCC | 47K| | |
    R1| | + | | | o-----.
    | | | | '-' | |
    '-' .---o----o---. | |/ |
    | | 8 4 | '----| |
    | | | |> |
    o-----o 7 | | | VCC
    | | | | | + .----------.
    .-. | | === | | | |
    R2| | | 555 | GND | | | |
    | | .--o 6 | | | | |
    '-' | | | .--------o-----o------o-------. |
    | | | | | RST Vdd CLKEN | |
    o--o--o 2 3 o--------o CLK | |
    +| | | | 4017 | |
    C --- | 1 5 | | | |
    --- '---o----o---' .--oVss | |
    | | N.C. | | "0" "1" "2" "3" "4" "5" "6" | |
    === === | '--o---o---o---o---o---o---o--' |
    GND GND === | | | | | | |
    GND | | | | | o-----'
    | | | | | |
    10K.-. .-. .-. .-. .-. .-.
    all| | | | | | | | | | | |
    | | | | | | | | | | | |
    '-' '-' '-' '-' '-' '-'
    | | | | | |
    v v v v v v



    VCC
    +
    |
    |
    V ~ Amber
    - ~(Green)
    |
    |
    .-.
    | |
    | |R5
    '-'
    |
    From 4017 & |
    10K Res. |/
    >---o----| 2N3904

    | |>
    .-. |
    10K| | |
    | | |
    '-' |
    | |
    === ===
    GND GND
    (created by AACircuit v1.28.5 beta 02/06/05 www.tech-chat.de)

    Note that each of the 4017 outputs also goes to a transistor as shown,
    with the terminal "6" driving a green LED instead of an amber one.
    I've left the choice of resistor values to you depending on what kind
    of power supply you use and what kind of timing you'd like. For a 5VDC
    supply and 1 second Christmas Tree timing, you might want to try 470K
    for R1 and R2, 10uF for C, and 220 ohms for the 6 ea. R5. I'd
    recommend against using the 3VDC of the receiver for the rest of the
    circuit -- it won't interface properly here -- use the external,
    regulated supply.

    So, about 1 second after you press the doorbell transmitter, the amber
    "1" will light up, 1 second later the "2" will light up, and so on. 5
    seconds after doorbell press, the green "6" will light up, and stay on
    for however long the 1st 555 is on (about 10 seconds above). That's
    because the "6" is also driving CLKEN. As long as that's low, the 4017
    will clock. When it goes high, the 4017 will stop clocking no matter
    what's going on at CLK. But after 10 seconds, the 1st 555 will go off.
    At that time, the 4017 will be forced into reset and all the lights
    will go off until you press the transmitter button again.

    If you don't want to use LEDs, you might want to use the transistor
    outputs to drive other transistors, small relays, or use logic level
    TO-92 triacs to drive a low voltage AC bulb. Your call.

    Try this circuit out as it stands, though, and see if it works. Feel
    free to post again if you've got other questions.

    Good luck
    Chris
    Chris, May 16, 2005
    #7
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