Alarm Contact

[Pesticida]

Thanks to all for the answers,but what command I now need to measure this Voltage I have a PIC16F870 with 20Mhz .
What happend when i have a wire ~ 100-300 Meter long.
I dont know how sensitive is a PIC controller.

Thanks a lot People!!!

Bye Pesti.

[Pesticida]

I think that I can use the Alarm circuit like on my draw !?

I have three States,Cicuit :
Magnetic Contact is closed: No Alarm (5K6 Ohm)
Magnetic Contact is Open: Alarm (6K4 Ohm)
Cable Tamper or Alarm Box Tamper is open : Sabotage
ShortCircuit on the loop : Sabotage


The Contacts are inside a door and on the Security side Zone.
I think so is ok or ?
Bye Pesti.

[Darrel Taylor]

Well, I don't have 30 years experience at anything, except "Beer Processor".   I just pour it in one end, and it comes out the other in about a half an hour.   So, maybe I'm not the guy to listen too....but...


It seems to me that most alarm systems are contained within the same perimeter that it is protecting. While the movies always seem to have a key element of the system located in an unsecured area where it can easily be defeated by cutting a couple wires and using some alligator clips.   That's not very realistic.

If any tampering is going to be done to the system, you would first have to breach the perimeter to get to the wiring in the first place. Which of course would set off the alarm.

So, the time when the tampering occurs, is when then system is dis-armed, and people are walking around everywhere unchecked. If you can by-pass sensors during the day, you can come back at night and clean the place out.

In the case of alarmbox.BMP in post #9, all you need to do is twist the two pairs of wires together, and your done.

And, in Luciano's example, you can just bypass any switch with a short, and you're in.

Not secure system

+5 --R2--+
         |
AN0 -----------------S1--------S2-------S3---------S4R1--+ 
                    |__|      |__|     |__|              |                                                 
GND -----------------------------------------------------+

Personaly, I think you are better off using the original plan.

And, you would use the ADCIN statement to read the input. I think that's what you're prior question was??

[Melanie]

Most alarm systems I've come across have a series Resistor in each Sensor. Attempt to bypass the Sensor (with Darrels aligator clips) and you unbalance the circuit setting the Alarm off. But hey, who am I to comment... I'm not thirty yet!

[Pesticida]

Ok thanks people,now I know what i have to do.
I made a Security Software in Visual Basic,for the moment for 4 Alarm Contact.
I have work two week on this Software,the most lost time was on the PIC
controller.

Thanks !!!
Bye Pesti

[Normnet]

I think this was from Forrest Mims. Intelligent Alarm.

Alarm resisters of different values in series.
Each window/door if opened closes across a resistor?
Total resistance (Pic AD) indicates which resistor is shorted.
Even with combinations of resisters shorted it can be determined which windows are opened.
Tamper is if not one of the combinations.

Norm

[Luciano]

Hi,

What about an alarm system based on RS-485 supporting up to 32 devices (even 128)
with maximal network length of up to 1500m?

With the master PIC you could:

- Query the status of the slave PIC.
- Reset the alarm status of the slave PIC.
- Turn the light on and off inside the room via slave PIC.
- .....
- .....

Also with the VB program talking to the master PIC via RS-232 you could
dynamically define areas which are protected also during the day and monitor/log
the activity of each slave and and therefore know which window/door you will
have to check before you leave the building.
What about verify the temperature of the air-conditioning in the computer server room?
There are no limits here.....

Best regards,

Luciano
Star Trek Security Systems