Security Alarm project
Hello people,
I am new to electronics so please be kind![turn.gif](http://forums.parallax.com/images/smilies/turn.gif)
I want to make security alarm project for my home and I am thinking of using around 11 PIR sensors (motion control) and some sensors for the doors ( the open-close switch for the doors ).
The idea is that I will connect a GSM module (Noklia N12i) and finally the module will send me an sms message if the alarm is raised. And of course some beels will ring.
My problme that I think that I will have is the following:
I will need several meters of cable in order to place all the sensors. I haven't used wireless because it is more expensive and because I have already purchased the sensors![burger.gif](http://forums.parallax.com/images/smilies/burger.gif)
Do you think that the signal will be lost because of the wire's length ?
Will I need something like a repeater to reapet the signal ?
SOme informations would be useful.
Thank you in advance
I am new to electronics so please be kind
![turn.gif](http://forums.parallax.com/images/smilies/turn.gif)
I want to make security alarm project for my home and I am thinking of using around 11 PIR sensors (motion control) and some sensors for the doors ( the open-close switch for the doors ).
The idea is that I will connect a GSM module (Noklia N12i) and finally the module will send me an sms message if the alarm is raised. And of course some beels will ring.
My problme that I think that I will have is the following:
I will need several meters of cable in order to place all the sensors. I haven't used wireless because it is more expensive and because I have already purchased the sensors
![burger.gif](http://forums.parallax.com/images/smilies/burger.gif)
Do you think that the signal will be lost because of the wire's length ?
Will I need something like a repeater to reapet the signal ?
SOme informations would be useful.
Thank you in advance
Comments
But because I am new I would like a bit more help if you want.
Are u able to give a general diagram of the connections that you have made ?
From the little that I have read for the rs485 is being used for intranets if I am not wrong.
Do we know the max length that it can safely send/receive the signal ?
Is it something like a filter that takes out noise ?
In addition I am not sure if we have the same name here (europe) for the "cat5" cable.
Do you use PIR sensors?
"With RS485 communication distances of 1200 m are possible."
http://www.lammertbies.nl/comm/info/RS-485.html
http://www.national.com/pf/DS/DS3695A.html
First, that chip looks fine, can't remember which one I'd picked out at Digi-Key. Think it was the cheapest that Digi-Key sells singles of.
At the sensor end:
Hook the output of the sensor to pin 4 (DI).
Tie 3 (DE) and 2 (RE) high (VCC) to enable the transmitter and disable the reciever.
Hook 6 & 7 (DO and _DO) to the wire.
Use the spare wires in the cat 5 as power. (I was going to use 7-12 volts and have a regulator on the board too.) Cat 3 might be cheaper, but I have a roll of cat 5 laying around.
At the stamp end:
Hook 1 (RO) to the stamp.
Tie 3 (DE) and 2 (RE) low (GND) to enable the receiver and disable the transmitter.
Hook 6 & 7 (RI and _RI) to the wire. (I think it's pin 6 to pin 6 and pin 7 to pin 7, see datasheet).
You also need a RT at the stamp end. The larger the value, the less current you need at the sensor, but the more problems you might have with noise. I was going to play with this, as my wires aren't going to be super long, but can't even guess where to start. (well maybe a 1K to start, long wires would need smaller values, see the datasheet)
BTW, I was also thinking of expanding my idea to a security system, so once I start, I'll let you know how mine works out. (late this fall at with current plans) Sorry I can't help more, but I can't even program a stamp here. :-(
I will take one RS485, datasheet, your informations and I will try to see what I will make up with all of them [noparse]:)[/noparse]
In case you have something new please let me know. I will do the same.
Regards
exp1
Column #28: RS-485 Transceiver for Reliable Network Communications