Adding second trigger to SSR

Discussion in 'The Projects Forum' started by Hobbes159, Jul 5, 2012.

  1. Hobbes159

    Thread Starter New Member

    Jul 5, 2012
    I have a very simple circuit that works quite well (see attached Drawing1). A 120VAC siren is activated by using a solid state relay; the relay is triggered by a simple SPST switch running 12VDC.

    There is a 120VAC > 12VDC power supply, a few LEDs for illumination, and the SSR, all mounted in a weatherproof box outside.

    What I'd like to do is to activate the siren by one of two methods: either by pressing the existing button outside, or by remote control via radio. I have an existing DTMF-controlled relay connected to a radio about 50 feet away. When the DTMF controller detects the correct code from the radio's received audio, it closes a relay which supplies 12V, which I'd run outside to the existing box. I'd like to use this switched 12V supply to also trigger the SSR.

    My concern is that I've now got two different sources of 12V running to the SSR, and two potential paths to ground, and in my head it just doesn't seem right. (See attached Drawing2).

    Any suggestions?
  2. Wendy


    Mar 24, 2008
    Welcome to AAC!

    I found this post automoderated by the forum software. I have approved it.
  3. strantor

    AAC Fanatic!

    Oct 3, 2010
    why use a second source? either way you have to run 2 wires. You're using a relay, so I would just take 12V from the existing power supply, run it to the relay, and back to the other side of the existing switch. To put it another way, place the relay contact in parallel with the existing switch.