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Relay Help - 8.5 VDC

Discussion in 'General Electronics Discussion' started by shockuk, Jul 25, 2010.

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  1. shockuk

    shockuk

    4
    0
    Jul 25, 2010
    Hi all,

    I'm currently setting up a house alarm system. I have an external bellbox that requires 12 volts DC to "trigger" it's speaker. However, my alarm control panel outputs 8.5 volts as it's trigger output.

    I have attempted to use a 12v relay, but the 8.5v is not enough to trigger it. Looking online, it seems that 12v relays require 9-15 volts. Alternatively, a 6v relay requires 4.8-7.2 volts.

    I couldn't find any information on a relay that could be switched at 8.5 volts.

    Does anyone know of a solution?

    Thanks very much,
    Shockuk.
     
  2. Externet

    Externet

    754
    164
    Aug 24, 2009
    Your +8.5V------------|>|---------|>|--------|>|----------6 V relay---------------gnd
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,473
    2,819
    Jan 21, 2010
    Externet's answer is a good one (especially if you already have the relay).

    On the other hand, there are a plethora of 9V relays available which would presumably do the job.

    I'm assuming that the output signal is designed for switching a relay (seems fair since it's coming from an alarm system) but I would check to see what voltage you get when the alarm is running from batteries (presumably it has battery backup). If the internal battery is a 6V lead acid battery, the voltage may be substantially lower if the power has been off for some time.

    My recommendation would be to measure the voltage when power has been cut to determine if it falls any lower. You may need to take that into account.
     
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