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Intelligent Remote Trigger Alarmy Thing

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computer

New Member
Hi,

I'm quite into electronics, but I find it hard to work out the basics of my circuits. I just found these forums, so I hope some of you can help me design this.

What I was thinking of is designing this to be used in a burgular alarm. Eventually, it might not be but it might, if you know what I mean.

So, here is what I am thinking of...

You have a big control box, which will decode the signals from a 6 core alarm cable and then handle it in a programmed way via some PICs or something. So, say you have an 8 zone, plus PA and Tamper alarm. That is really 9, as all sensors have tamper.

Then, connected to each device is a little encoder box. What it does is take the 6core cable in, which also goes through to other devices in a chain and it converts it to probably 12v, 0v, Signal + and Signal -. A PIR would connect to the 12v and 0v for power, and the signals are what its outputs are. A magnetic contact would use just the two Signal lines.

This is what I suggest the cable could be:
1 - 12v
2 - Alarm/Tamper
3 - Signal +
4 - Signal -
5 - Clock
6 - GND

What you could have is a DIP switch, that will let you select the sensor ID, and if it was a 4 way dip, you could possibly get 4x4x4x4 devices on the whole system which is about 256. Another DIP set would allow you to select the zone, from 1,2,3,4,5,6,7,8 and PA. The tamper/alarm line would have pulses going down it at the same rate as the clock line, which is controlled by a 555 or something to give short pulses. You might not need the Signal - line, I don't know. If the tamper/alarm line is pulsing at on-off-on-off-on-off then it is okay, but if it is off-off-off-off-off then there has been a tamper attack, ie wires cut. If its on-on-on-on-on then if an alarm is connected to a relay between 6 and 2 it would connect the alarm.

The clock pulse would allow the devices to send their status to the control panel. Each cycle, the next device would send on for all okay or off for bad, or tamper becuase of cut wire. It would go all the way up to 256, then back to number 1.

If there was an activation, it could trigger the alarm, the siren in the control panel and perhaps display the activated device on a little LCD...

what do you think, and is it possible, if so how?

thank you,
computer
 

Dialtone

New Member
Do a Google search on I2C or SMBUS devices. They work basically on a small high speed serial bus like you described using 4 wires. Each device is addressable, and you can chain many together on a single bus.
Dialtone
 
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