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Microprocessor for alarm system

Discussion in 'Electronic Design' started by Myauk, Jun 27, 2007.

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  1. Myauk

    Myauk Guest

    I am going to design an alarm system including smoke, gas alarm and
    I am asked to use the microprocessor for it.
    Using a microprocessor, I think I can add more features to the alarm
    system yet I do not know what are the availble features of such
    Can anybody suggest the suitable microprocessor for it?I don't want to
    use the old intel 8085 for it.
  2. JeffM

    JeffM Guest

  3. Myauk

    Myauk Guest

  4. First of all, why bother?
    There are plenty of fully built and fully debugged alarm systems on
    the market, they can be configured to do anything you want.
    The last thing you want with an alarm system is for it to be
    unreliable in either hardware or software. Someone else has already
    spent years debugging the hardware and firmware to make them reliable.
    You'll be starting from scratch.
    That might be fine for just an intruder alarm, but when you start
    talking smoke and gas sensors, you are talking about people's lives
    here, so don't muck around and try to do it yourself.

    But if you *really* want to do it, practically any 8bit micro will do
    the job, it's just I/O, nothing fancy required on the micro side. All
    the input protection/windowing and output drivers are all still done
    in discrete hardware.

    Or is this an assignment?

  5. JeffM

    JeffM Guest

  6. Eeyore

    Eeyore Guest

    You need a *microcontroller*.

    If you're familiar with Intel products, check out the 8051 family and its
    varaints from many many vendors.

  7. Eeyore

    Eeyore Guest

    How much more work do you expect to get done for free ?

    You need to start by writing (or just thinking through) a system specification.

  8. mpm

    mpm Guest

    Many residential / commercial burglar & fire alarms have the following
    general characteristics:

    1 - Output relays (usually several, and each is programmable by
    2 - A secure communications protocol to contact the authorities
    (monitoring station)
    3 - A secure communication bus to "talk" to user keypads
    (alphanumeric, numeric-only, even key switches, etc...)
    4 - Support for multi-zone operation. (Some areas can be secured,
    while others remain off. etc..)
    5 - Power limited circuits for fire protection devices
    6 - Integrated siren driver circuits, perhaps with different sounds
    for different types of alarms.
    7 - Automatic low-battery cut-off circuits (to avoid damaging backup
    battery during prolonged outages)
    8 - Switched power supply (to reset certain commercial smoke
    9 - Wireless sensor compatability, though this is usually done as an
    10 - A "Panic" feature (duress) which makes the panel behave as if
    it's been deactivated correctly, when in fact it is calling the
    11 - Various door access controls (using same keypad as arm/disarm),
    but can be used when the alarm panel is not secured (armed). For
    example, to open a gate or door.
    12 - A "chime" function, to announce arrivals when the system is
    13 - An alarm printer port (for hard copy printout)
    14 - Various "zone extenders", to minimize wiring in larger
    15 - Output controls to operate video recorders (during an alarm

    This should get you started.
    Oh, I fogot an important one: Support for both slow and fast loop
    Some sensors work better when they are looked at slowly over time,
    whereas others can be so quick (like piezoelectric), that you need to
    "stretch" their pulse out to a reasonable length in order for the
    panel to "see" them correctly. This stretching is often done in the
    alarm panel, though it can also be accomplished with external

    Many alarms were built around the Z-80 (8085), though you will
    probably find a lot of circuits using 8051's and derivatives.

  9. Use some PIC.
  10. delo

    delo Guest

  11. Nico Coesel

    Nico Coesel Guest

    These days ARM7TDMI based microcontrollers are easy to get your hands
    on. They work very fast and are quite cheap.
  12. If you alarm is going to be a comercial product then for get doing anything.

    If this is your first project you should


    Define exactly what you want to do

    - how many sensors,
    - what type od sensors
    - how are they connected
    - what voltage and power is required
    - how will they signal back to the main unit?
    - how will you turn the alarm on / off..

    Basically look at other alarm specifications to make your own.

    Once you have this info.... you can start breaking down the design in to
    little bits... and work on one at a time.

  13. Myauk

    Myauk Guest

    Thank you so much for your suggestions
  14. Donald

    Donald Guest

    Do you have any experience with microprocessors/microcontrollers ???

    How much money do you want to spend ??

    Its nice to have a goal when starting a with a new technology,

    but it sounds like you have a lot of homework to do first.

    good luck

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