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Connect GSM alarm (12v) to electro-mechanical doorbell

Discussion in 'General Electronics Discussion' started by DCNoob, Oct 5, 2016.

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  1. DCNoob


    Oct 4, 2016
    I bought GSM alarm that uses 12v 1A power adapter.
    the cord is too short so I will have to use extension etc.
    So I checked the doorbell (electro-mechanical) that I have above my door and there is 12v output for the button.
    I want to use its output and connect my alarm to it,
    I checked it with multimeter and it shows 20v, then I pressed the ring button and it went down to 16v
    then I tried to press the button while I am holding the probes and when I press its voltage got to around 9v and then back to 16v.

    Doorbell uses ~230v, I don't have picture right now.

    Is it possible to connect my alarm to it?

    And one more question, if I will extend the cord of the power adapter to use longer cord will it affect the power adapter?
    I used 5.5x2.1 male and female and two ~2m thin wires.
    and after some time the adapter died, is it has something to do with the extension I made of some other reason?

    Also checked the resistance of the wire (1 cm of it) and it said 0.3Ω, then checked the full length (~3m) and it said 0.8Ω how is it possible?

    Thank you!
  2. HellasTechn


    Apr 14, 2013
    I think you better not.

    No i beleave extention is harmless if polarity is maintained and cable is not shorted and in good condition.

    Probably not if there was no short circuit.

    That has to do with the cable's quality. depending upon the material used, it's thickness and its condition in general (corrosion etc).
  3. DCNoob


    Oct 4, 2016
    Thank you for the answers!
    I know that I better not but it will be very neat and clean solution,
    So how can I do it?
    Should I use voltage regulator to make it fixed 12v but as far as I understood it can't boost voltage up?
    Also how can I check how many amps I have there?
  4. HellasTechn


    Apr 14, 2013
    I dont think you can.
    That is correct, a voltage regulator is not an option here.
    There is no way i can think of to check that because amperage is not like voltage, you can only monitor that under load and yet it may be capable of more than you measure. You could find out either based on the device model or if you can analyse the layout of the psu.
    Last edited by a moderator: Oct 5, 2016
  5. davenn

    davenn Moderator

    Sep 5, 2009
    and the main thing that hasn't been brought up is that the doorbell PSU is probably AC and not DC

    @DCNoob get a PSU that is correctly rated for your GSM module
    HellasTechn likes this.
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