Looking for resources for simple project

Discussion in 'Electronics Resources' started by likes_shiny_things, Oct 28, 2012.

  1. likes_shiny_things

    Thread Starter New Member

    Sep 11, 2011
    20
    0
    Since I know little about electronics, I was hoping someone could provide some advice on how the get my project done - which likely means pointing me to a place where I can purchase a schematic or hire someone to create one.

    The project:

    I need a device that will detect motion (probably PIR) and emit a sound (like a Sonalert). It shall run off 120VAC and have the ability to adjust the volume and duration of the sound.

    I know one can purchase off-the-shelf units that detect motion and emit a sound, but I have found none with adjustable volume and adjustable duration that the sound is activated.

    As such, can someone suggest how I may achieve this, whether it be:

    1) An off-the-shelf unit I have not been able to locate

    2) An existing schematic that I can purchase

    3) Where to hire someone who can draw a schematic for me

    I am familiar with online services such as Rent-a-Coder and Guru, but I don't know if those services are the best place to start if I decide to hire someone.

    I am quite capable of acquiring the parts and building it.

    Thank you for any suggestions!
     
  2. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    You could do this with a microcontroller, but if you haven't programmed before, this will add time and/or cost (if you plan to pay someone).

    These seems reasonably simple and you may not need much in the way of a circuit to do this. Based on your criteria, you could do this with a motion sensor from RadioShack and a sound module from BigDawgs. Some questions first:

    1. What kind of sound do you want to play, e.g., an MP3 or other pre-recorded sound or something you make like an electronic siren?
    2. How long do you want the sound to last at the max? In other words, what is the longest you want the sound to be able to play for - 30 seconds, 4 minutes, one hour, etc.?
    3. How loud do you want the sound at the max? For example, enough to hear across a room or a field?
    4. Are you looking to make a single unit and don't care how big the unit will be or are you looking to make several of these and need it to look a certain way and/or fit a certain size?
    5. What kind of distance for motion detecting are you aiming for, e.g., someone crossing a threshhold, entering a room, etc.?
    We can help you with design ideas and circuits you test and build yourself as part of the forum or I can make it myself for some fee depending on the requirements. If you're interested in making this yourself, we can guide you - this way you'll learn more, get hands-on experience, and only spend money on parts, not someone's labor (other than your own, but that's free right?) . :)
     
  3. likes_shiny_things

    Thread Starter New Member

    Sep 11, 2011
    20
    0
    What kind of sound do you want to play?

    As I suggested, I figured I'd use something like a Mallory Sonalert so there would be no need for any audio input, processor, or programming. The Sonalerts have a variety of sounds from which I could choose. (However, I'm not sure a Sonalert's volume can be adjusted - regardless, I would think a small, self-contained noise maker of some type would be available)

    How long do you want the sound to last at the max?

    I intend the sound to last about 2 to 5 seconds, but it would be nice to have the option to go as long as 60 seconds.

    How loud do you want the sound at the max?

    85dB @ 1 meter

    Are you looking to make a single unit and don't care how big the unit will be?

    One unit. I was hoping for an enclosure about 5 x 5 x 8 inches or smaller.

    What kind of distance for motion detecting are you aiming for?

    Max. 12 feet, but actually more like 3 to 4 feet. I would like to make that adjustable as well, but such adjustment could be mechanical rather than electical.

    That's a kind offer to help me to build it and although I would love to learn more (I'm interested in just about everything!), I'm very busy starting a business. I was hoping the project was simple enough that someone's fee to design it would be affordable for me.

    I think it would consist of a power supply (it could even be a wallwart - which I already have a bunch of), a circuit for the PIR to activate the noise maker, and circuits to control the volume and duration of the noise maker.
     
  4. elec_mech

    Senior Member

    Nov 12, 2008
    1,513
    193
    Okay, I'm working through this, but I believe I can make something work. A few more questions:

    1. Would a PIR sensor capable of 15' and 30' (settable) be acceptable? The sensor could probably be aimed to some degree to reduce the detecting area. I was thinking about this: http://learn.parallax.com/kickstart/555-28027
    2. Some of the Sonalerts can be somewhat volume-controlled using this: http://www.mallory-sonalert.com/specifications/SCVC.pdf. The question is, do you want to use a specific Sonalert with this baffle or do you just want a loud sound with some volume adjustment? I could use a personal alarm and adjust the volume via voltage control (I think) or do the same with a buzzer/siren. I could get crazy and look for a circuit that controls the volume and type of sound out of a piezo element if you want more play with the sound.
    3. Since it is possible to have the siren reset and sound continuously if the PIR sensor is being repeatedly tripped, would you like some hysteresis built in? As an example, say someone is tripping the PIR sensor and the siren is set to go off for 3 seconds. If the PIR sensor is tripped constantly (someone is standing in front of it for more than three seconds) do you want the siren to go off continuously or go off after a period of time, say one minute? So PIR is tripped, siren sounds for 3 seconds, then won't sound for one minute regardless if PIR is tripped or not. The pause time could be made adjustable.
    PM me with your desired budget and I'll go ahead and do some experimenting - no obligation at this point of course. ;)
     
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