Microprocessor for alarm system

Hello, I am going to design an alarm system including smoke, gas alarm and buzzer. 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 systems. Can anybody suggest the suitable microprocessor for it?I don't want to use the old intel 8085 for it. Regards

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I am now reading the notes from wikipedia. But still I need some suggestion from practical people Regards

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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?


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David L. Jones

Apparently you skipped the first day of class or your instructor jumped over the first chapter:

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

1 - Output relays (usually several, and each is programmable by event) 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 detectors) 9 - Wireless sensor compatability, though this is usually done as an add-on. 10 - A "Panic" feature (duress) which makes the panel behave as if it's been deactivated correctly, when in fact it is calling the police. 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 disarmed. 13 - An alarm printer port (for hard copy printout) 14 - Various "zone extenders", to minimize wiring in larger installations. 15 - Output controls to operate video recorders (during an alarm event).

This should get you started. Oh, I fogot an important one: Support for both slow and fast loop response. 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 circuitry.

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


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On a sunny day (Tue, 26 Jun 2007 18:02:21 -0700) it happened Myauk wrote in :


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Jan Panteltje

try this link:

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it's in italian language...

bye delo

"Myauk" ha scritto nel messaggio news: snipped-for-privacy@c77g2000hse.googlegroups.com...

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These days ARM7TDMI based microcontrollers are easy to get your hands on. They work very fast and are quite cheap.

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Nico Coesel

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.


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Joe G (Home)

Thank you so much for your suggestions Regards

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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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