Newby - 6 volt trigger

Discussion in 'The Projects Forum' started by Cowombat, Jan 12, 2012.

  1. Cowombat

    Thread Starter New Member

    Jan 12, 2012
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    Hi all, my first post. I am just about zero in electronics knowledge, so had trouble identifying the correct key words for a search in the forum. So please accept apology if I should have found the answer already posted!!

    Situation. I moved into a two storey rental house, so can't punch holes in walls etc. The door bell is downstairs and I can't hear it upstairs. I want to put in an extension ringer.

    The existing doorbell is part of a mains powered 25 year old Electron Home Comms system. There is:
    (1) a push button switch at the front gate (50 meters away and I can't replace it, and I don't want a second switch installed there)
    (2) stepdown transformer somewhere hidden behind the internal walls delivering 6 volts (I can't get to it, only have access to the 6 volt wires
    (3) 6 volt Friedland brand chimes (accessible)

    What I tried to do:
    I purchased a wireless doorbell system. The remote button unit can be opened and the PCB is accessible. My idea was to connect it in parallel to the wires from the cable that runs from the existing switch. So when the existing switch is closed, both (1) the old Friedland chime will ring and (2) the circuit will close on my new switch, triggering the wireless bell.
    Seemed like a good idea, until discovering I don't have access to the wire running from the original button.

    What to do next?
    Your help please! Is there a simple way (yes, I own a soldering iron) that I can take the 6v that goes to the old Friedland chime to trigger my new wireless switch? I.e. I just have to have a method to close the circuit on the new switch.
    Or is there some better solution altogether?

    Thanks!
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Pictures....are our Welcome Gifts. :D
     
  3. wayneh

    Expert

    Sep 9, 2010
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    How is the remote button powered - probably a small battery? It's possible you could power it from the chime ringer circuit. (You would "permanently" close the button switch). To pursue this approach, it would help a lot to know how much current the remote needs. Do you have a multimeter that can measure current in the ~100mA range? Put it in series with the remote's battery and see how much current the remote draws.

    There are other solutions, but this might be the simplest.
     
  4. Cowombat

    Thread Starter New Member

    Jan 12, 2012
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    Ah, I see your line of thinking. The battery in the remote switch is a small 12 volt item (VR-22). I don't have a multimeter, but can probably find a friend with one.
    But maybe first I just take a lead from your idea, running 6 volts from the original circuit straight to the remote with its switch closed. Never know till I try it, might be sufficient to transmit.
     
  5. wayneh

    Expert

    Sep 9, 2010
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    Most likely it will. But make sure the 6v ringer supply is actually DC. Putting an electrolytic capacitor in parallel, like it's a battery, may also help protect the circuit from a noisy power source. Since it's meant to run off a battery, it may not have a lot of protection built-in.
     
  6. MrChips

    Moderator

    Oct 2, 2009
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    We need to know a bit more about the Friedland chimes. Can you provide a model number?

    Once we know that, you will purchase a small reed relay. The coil of the relay will be wired in parallel with the chime. When the door bell button is pressed, it will send power to the chime and the relay in parallel.

    The contacts of the relay will be wired in parallel with your remote pushbutton. When the relay contacts close, the radio transmitter in the remote will be energized and will send a radio signal to your wireless which will be located in your apartment.
     
  7. Cowombat

    Thread Starter New Member

    Jan 12, 2012
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    It is a Friedland 117. I found the wiring diagram at http://www.tlc-direct.co.uk/Technical/DataSheets/Friedland/117.pdf
    My system is wired according to diagram 4(a)
    I can see from it that I was wrong in my original guesstimate of the circuitry.
    Because I don't have a multimeter, I'm not sure what DC voltage is coming from the transformer - but presumably in the range of 8-16v.
    I look forward to your advice as to the correct relay to install.

     
  8. MrChips

    Moderator

    Oct 2, 2009
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    I don't know where you are located but I'm guessing in the UK.
    If that is the case your AC mains is 240V and so I will guess that the transformer is putting out 16VAC. I would look for a 12VAC relay.
     
  9. Cowombat

    Thread Starter New Member

    Jan 12, 2012
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    Australia actually, so still 240 v. Thanks for the advice... I'll go get one!

    And definitely AC? Just wondering, given the alternative power source is DC batteries. Not doubting, just ignorant and wanting to be sure :)

     
  10. MrChips

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  11. Cowombat

    Thread Starter New Member

    Jan 12, 2012
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    Ah yes, my handle is a bit of a give away, eh? I've ordered the relay via the web. Getting harder to buy such stuff locally. An excellent retailer that was close by has rolled down the shutters...
    Thanks again for your help!
     
  12. Cowombat

    Thread Starter New Member

    Jan 12, 2012
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    Hmmm, not sure if my last message (of thanks for help) successfully posted. Maybe stuck in review.....

    Anyway one last question. I've ordered the relay; hopefully to get it early next week. But being non-technical, I'd appreciate advice on the wiring. The diagramatic is at http://docs-asia.electrocomponents.com/webdocs/0b61/0900766b80b6105a.pdf.
    What goes to what, please :confused:
     
  13. MrChips

    Moderator

    Oct 2, 2009
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    There are two relays shown in the product sheet with different styles of contacts. Either relay will work.

    [​IMG]

    The RED wires go to the relay coil. This is the same for both styles relays.
    The BLUE wires connect to terminals 11 and 14 on the relay. These go to the contacts on the wireless door bell button in effect performing the same function as the button.
     
    Last edited: Jan 13, 2012
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