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can you help with car alarm idea

Discussion in 'General Electronics Discussion' started by scubapro, Feb 11, 2012.

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  1. scubapro

    scubapro

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    Feb 11, 2012
    I have a 12 volt basic car alarm. It has 2 negative pulse outputs to operate door locks....lock/unlock. I use this alarm on my garage, works great. I would like to use the lock/unlock pulses to power a 12 volt latching relay, which would allow me to use the contacts to power a 120 volt light on the garage. So when I turn the alarm on, the outdoor 120 volt light comes on. When I tun the alarm off, the 120v light goes off. Do I only need one latching relay or two? (lock/unlock) Also, will I need an additional 12 volt relay to turn on the 120 volt circuit, or will the latching relay be enough. I am having a hard time picturing the schematic. I think an automotive style spdt latching relay will work, and they are cheap. I also don't understand the terminal numbers represent...such as 85, 86, 87, 87a, etc. Can you help?
     
  2. Rleo6965

    Rleo6965

    585
    9
    Jan 22, 2012
    Last edited: Feb 12, 2012
  3. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
  4. scubapro

    scubapro

    2
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    Feb 11, 2012
    Thanks, you guys are more advanced than me. I ordered a new alarm that will arrive tomorrow. Due to the fact that the old one was OLD! The remotes just would not cut it. I will then find out if I do in fact have one separate pulse for lock, and one for unlock. My fear is that if I hit "lock" twice, I will infact arm the alarm but turn off the light....see what I mean?
     
  5. Rleo6965

    Rleo6965

    585
    9
    Jan 22, 2012
    Try this simple circuit.

    Q1 and Q2 circuit configuration for Car Alarm output of 12V goes to 0V.

    If your car alarm output was 0V to 12V. Replace Q1 and Q2 circuit with Q3 circuit.

    Use small 12V relay for Q1 and Q2. Q3 might be bigger 12V Relay switch contact ampere. Depends on your load or Lamp.

    [​IMG]
     
    Last edited: Feb 13, 2012
  6. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    No, that won't happen. This type of relay has two coils.
    Coil1 ist for setting the relay, coil2 is for resetting the relay. Once the relay is set, any further pulses on the set coil will have no effect (apart from consuming a bit of power). And vice versa, once reset, any pulses on the reset coil will have no effect. Only alternating pulses on set and reset will make the relay switch.

    Harald
     
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