Alarm system with PLC

[PinksteR]

Hi, i need some help folks, in workshop class we were asked to build a house alarm system (4 zones, window and door security, etc..) and we have a PLC to use.
So we have to try to assemble a CHEAP (20 bucks max) system that uses the PLC to control the alarm.
I have been looking around and i found millions of alarm systems to build, but they all use ICs and as i have to use the PLC i think they are not suitable. Also they look expensive to build.
What would be the simplest way to build a movement sensor or a magnetic sensor for the doors and windows?
I really apreciate any help you guys can give.
Thanks

 

[williB]

magnetic sensors can be and usually are " hall switches" which can be found in burnt out pc power supply fans..

 

[Kobejitsu]

alarm

Well... i saw some other day, a magazine that talked about the various kinds of sensors that could be used in alarms, the simpler kind is a form of pressure switch that is closed when the windows is closed, of couse this is a very basic aproach but if you run out of ideas maybe you can give it a try . Good luck

 

[williB]

PinksteR
sure you could allways use a micro switch..they have normally open and normally closed connections and some/most have a little roller built onto the end of the lever..

 

[chemelec]

The Simplest and Cheapest way is a "Reed Switch" and a "Magnet".

Next Simplest is a Magnet and a Hall Effect Switch, such as a TL170.
I Have these TL170's for sale on my Website.
**broken link removed**

 

[chemelec]

Correction:

**broken link removed**

 

[PinksteR]

thanks a lot guys, this gives me a lot of things to start researching about.
I'll research about hall switches, Reed Switch and magnet switch.
williB, can u explain a little more about the magnetic sensors in power supply fans? cause i have lots of fans and it could be very usefull.
Thanks

 

[williB]

https://www.electro-tech-online.com/threads/rf-signal-mobile-phone-detector.12308/#post-64651
it is best to get the whole board intact...

 

[PinksteR]

thanks williB!
Research went excelent, i like the idea of the reed switches in first place, but i'll try the hall switches too cause i have a lot of fans to use.
So the issue of the security system for the doors and windows is almost solved.
I also like a lot the project i found in chemelec site (**broken link removed**) cause seems to be very nice and cheap.
The only thing that have me concern now is the motion detectors, i cant find a way to do this cheap, the projects that use PIRs and fresner lenses seem to be expensive, and ultrasonic motion detectors the same, but maybe i havent found the most simple project using those systems.
If anyone have an idea it's welcome

 

[PinksteR]

I have a question about Hall switches, i cant see how i can use one of this switches for a door/window alarm, because of what i know about hall switches is that one magnetic pole turn them on and the other magnetic pole turns them off, but what happens if it isnt under the influence of any of them? is it on or off?

In the case of the Reed Switches it's much more simple, cause it's just a contact that is open if no magnetic field avalible and closed if a magnet is close to it.

 

[Nigel Goodwin]

I have a question about Hall switches, i cant see how i can use one of this switches for a door/window alarm, because of what i know about hall switches is that one magnetic pole turn them on and the other magnetic pole turns them off, but what happens if it isnt under the influence of any of them? is it on or off?

In the case of the Reed Switches it's much more simple, cause it's just a contact that is open if no magnetic field avalible and closed if a magnet is close to it.

It would seem an excessively complicated way, reed switches are normally used in alarms, simple, cheap, reliable!.

 

[Roboticinfo]

reply

Try this website


https://www.commlinx.com.au/schematics.htm

 

[PinksteR]

k. so i'll use Reed switches for the door/windows security.
Also i'll use a couple of lasers in the main room just for fun.
But my main concert still is the motion detectors, all the PIR motion detectors projects i saw seem to be very complex and expensive to build.
I need something as simple as possible and as cheap as possible.
As i'll be using a PLC im sure it can be done with just a PIR and a few components and without all those ICs they use in all those projects out there.. but i cant find out how to do it.

 

[Nigel Goodwin]

k. so i'll use Reed switches for the door/windows security.
Also i'll use a couple of lasers in the main room just for fun.
But my main concert still is the motion detectors, all the PIR motion detectors projects i saw seem to be very complex and expensive to build.
I need something as simple as possible and as cheap as possible.
As i'll be using a PLC im sure it can be done with just a PIR and a few components and without all those ICs they use in all those projects out there.. but i cant find out how to do it.

Just buy PIR's, they are freely available for burglar alarms, they are not really something you could build yourself, due to the freznel lens and focusing required. They have standard connections to connect in to burglar alarm systems.

 

[Ionela]

Hi, i need some help folks, in workshop class we were asked to build a house alarm system (4 zones, window and door security, etc..) and we have a PLC to use.
So we have to try to assemble a CHEAP (20 bucks max) system that uses the PLC to control the alarm.
I have been looking around and i found millions of alarm systems to build, but they all use ICs and as i have to use the PLC i think they are not suitable. Also they look expensive to build.
What would be the simplest way to build a movement sensor or a magnetic sensor for the doors and windows?
I really apreciate any help you guys can give.
Thanks

Hey,
here you'll find how to do the alrm system:
**broken link removed**