How to use low voltage (for audio speaker) to close a switch

Discussion in 'The Projects Forum' started by Tommy S, Jan 21, 2015.

  1. Tommy S

    Thread Starter New Member

    Jan 21, 2015
    4
    0
    Hi Everyone,

    I am an electronics novice (so type S L O W L Y) though I'm a fairly quick learner when it comes to tech-related stuff. I have seen a few posts about using a voltage sensor of some sort to trigger a relay, but they all seem to operate in the >5v range. What I am looking to do is disconnect the internal speaker in an alarm system and use the voltage from the speaker wires to trigger a sound file player such as this one:

    http://www.pricom.com/Trains/DreamPlayerLITE.shtml

    or this one:

    https://learn.sparkfun.com/tutorials/wav-trigger-hookup-guide

    Each of these have an input for an external normally-open switch.

    Essentially, I would like to not hear the annoying, screeching alarm, and instead have it play a sound file of my own creation. I am also considering using an Arduino to activate other mechatronic functions, so I guess it may be possible to use it to do this too, however my Arduino knowledge is very limited to simple robotics projects and I don't know a lot about I/O options.

    The other trick with this project is that ideally, I would like for the switch input to the player to stay closed for the entire time that the alarm is sounding (or rather, soundlessly outputting audio voltage) which would be a predictable but certainly varying waveform. So it would be best if the voltage sensor could have a variable threshold setting and a variable hold/release setting, similar to a gate or expander in a recording studio setup.

    Or maybe I'm overcomplicating this, so I'm open to any suggestions you may have. Thanks in advance for your wisdom and guidance!
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,059
    3,822
    Yes, you have overcomplicated this with options. Each option you mention has a different path to a solution. When you ask for advice, you should have a goal at the very least. A plan to get to that goal makes things better. And an understanding of all the steps to execute the plan helps even more. Also, if you talk about other equipment or tools, make sure you know how they work and what they do to help you.

    You have so much jibber-jabber going on that it makes my head hurt. So, my suggestion, that you asked for, would be
    1) set a goal (ONE GOAL).
    2) develop ONE PLAN with all the steps (modules) needed to EXECUTE THE GOAL.
    3) decide which of those steps in your plan you can complete and which you cannot.
    4) If you find circuit-related steps that you cannot complete, then come here and make a post.
    5) if you find your plan to be overwhelming, consider different plans.
    6) if you cannot find any plan to execute your goal, change your goal and start over.
     
  3. Reloadron

    Active Member

    Jan 15, 2015
    963
    232
    Yes, it can be done, likely several ways. However, we need to know what the signal is going to the existing speaker, exactly what the signal looks like. Once that is known a threshold detector circuit can be built and triggered by that signal and the threshold detector could then in turn trigger either of your devices. It all starts with knowing what the existing signal to the speaker looks like.

    Ron
     
  4. Tommy S

    Thread Starter New Member

    Jan 21, 2015
    4
    0
    Got it. I'll simplify the goal:

    I would like to have all the functionality of my alarm system except for the siren sound, and instead have it play a sound file of my own creation, through my own speaker system. I want the sound file to continue to play for as long as the alarm is activated.
     
  5. Tommy S

    Thread Starter New Member

    Jan 21, 2015
    4
    0
    I won't be able to know this until I purchase the alarm system, but I was hoping to work out this issue before purchasing it, if possible. However assuming I do go ahead and get the system, how would I go about getting the information you need? Would I need an oscilloscope?
     
  6. #12

    Expert

    Nov 30, 2010
    16,310
    6,817
    A big siren might only need a DC power wire to do its alarming thing. If the siren makes its own sound from just a power line, you've got this whipped. If the siren sound is generated on the circuit board, it is going to carry a lot of power to the siren. This simplifies things because there are only 2 choices and each of them carries quite a lot of power.
     
  7. Tommy S

    Thread Starter New Member

    Jan 21, 2015
    4
    0
    Okay, great. So it sounds like the concept is feasible, and I just need to get the system and parts to give you all the next level of detail. I will come back with more information when I have the equipment.
    Thanks!
     
  8. Reloadron

    Active Member

    Jan 15, 2015
    963
    232
    Absolutely feasible and possible. Just a matter of knowing what we have and working from there. :)

    Ron
     
    #12 likes this.
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