fire alarm control panel- urgent

Discussion in 'The Projects Forum' started by jane, Nov 27, 2007.

  1. jane

    Thread Starter New Member

    Nov 27, 2007
    1
    0
    HELP! right, im an electronics student at A level but my teachers ill and im ment to be making a fire alarm control panel with a bunch of relays and 2 pic. i know the basics but not how to wire it up and as you can guess its quite critical because its my A level! it has 2 have 2 zones.
    thanks
    jane
     
  2. Voltboy

    Active Member

    Jan 10, 2007
    197
    0
    How exactly it needs to work, how you plan on making it work?
    Do you need to actually make something for detecting the fire?
    Do you have any schematics or anything?
     
  3. RiJoRI

    Well-Known Member

    Aug 15, 2007
    536
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    First of all, let me say that I design alarm panels for a living. We use rather large micros, so I am guessing that one PIC does not have either enough I/O ports, or not enough processing power. In either case, they will need to communicate with each other. Do you have that? (Or will each PIC operate one zone?)

    What are you using as your detector? How does it communicate with the panel? (The panel refers to the panel where the micros are.) The communication be as simple as a switch closure. Incidentally, we use a 2K end-of-line resistor (EOLR) to determine if the zone is open or shorted or normal.

    I am going to guess that yours will be a stand-alone system -- that is, it will not try to communicate with a Central Station, but simply close the relay(s).

    So, ignoring UL, SIA, and the NFPA :D, the simplest system would have two input zones, each having an EOLR, and the sensors would be set up to operate as shorts across the EOLRs. The inputs should go to some kind of A/D converter to detect opens, shorts, and "normals". You should have some type of static protection on the inputs, and your software should debounce the inputs to help prevent false alarms.

    Also, fire alarms need to have a particular cadence. It is 3 dings and a pause, repeated. I believe the timing is 1/2 second for the ding time, and 1/2 second for the "interding" time, and the pause is 1 second. It sounds as if every fourth ding is missing.

    How do you plan to reset the alarm? While we use keypads with displays, you may be able to get away with a keyswitch -- that's a lock which closes a switch instead of mechanically moving a bolt. It can be imitated with a SPST N.O. switch.

    HTH,

    --Rich
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    Aha! You work for Notifier, eh?:p

    Yes. Ending pause is 1.5 seconds - but I had to look it up. (ANSI S3.41)

    Strobes! Don't forget the strobes.

    A lot of panels will use diodes in the notification appliances. The panel will use one polarity for supervision and the opposite polarity for alarm.
     
  5. RiJoRI

    Well-Known Member

    Aug 15, 2007
    536
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    Not really. I was hired by Ademco, which was bought by Honeywell. In between, I think Notifier was picked up by Ademco. (If ya can't beat them, buy them! ;) )

    Since this is a school project, I tried to keep the design simple: let the relays control all signaling devices: sounders, strobes, etc.

    --Rich
     
  6. gerty

    AAC Fanatic!

    Aug 30, 2007
    1,153
    304
    Rich, you could've made it interesting with 4 wire smokes and a EOL power good relay... :)
     
  7. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    Or delved into the intricacies of elevator shaft requirements.:D

    As RiJoRI said... its a school project. Better to keep it simple. Poll the initiating loop(s), and set conditions appropriately.
     
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