fire alarm control panel- urgent

Thread Starter

jane

Joined Nov 27, 2007
1
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
 

Voltboy

Joined Jan 10, 2007
197
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?
 

RiJoRI

Joined Aug 15, 2007
536
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
 

thingmaker3

Joined May 16, 2005
5,084
So, ignoring UL, SIA, and the NFPA :D
Aha! You work for Notifier, eh?:p

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.
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.
 

RiJoRI

Joined Aug 15, 2007
536
Aha! You work for Notifier, eh?:p
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
 

thingmaker3

Joined May 16, 2005
5,084
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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