Cross Zoning, not just two sensors...

[Peet_Skeet]

Hi I am trying to set up an alarm system with 10+ sensors used for out doors. But out of all these sensors I tend to give one or two false alarms a week, so I want to make it that any two sensors have to be triggered before it sends an alarm. This is similar to cross zoning but any two sensors, in any order, can be triggered before the alarm is activated.

PS this is my first time posting a new threrad so i hope it is right...

 

[KMoffett]

What are the sensors? How are they powered? What are their outputs? What is the circuit that they are feeding? Maybe, more details and a schematic of what you currently have?

Ken

 

[Peet_Skeet]

Sorry about that.
With the sensors i can choose to have either a N/O, N/C, or a 12VDC output. It's going to be feeding a ProSYS keypad system which inputs I can also modify to use N/O, N/C or 12VDC.
I would just like to know if you get a circuit board or a method that can do this, that i can do/insert between the sensor and the alarm system, and where to get it/how to do it. I am going to completely redo this current system so its schematic is not important.

 

[KMoffett]

Lots of possibilities, but I'm not familiar with the ProSYS keypad system. Does it need to identify which two of the ten sensors were tripped, or just that two have been tripped?

Ken

 

[Peet_Skeet]

Just that two sensors were tripped, i don't need to know which ones where tripped or in what order, because they are close together. To give you an idea of what I am looking for 'more or less' I have come up with a lay out in which if sensors 1&2, 1&4, 2&3 or 3&4 is tripped it'll trigger the alarm(there's 4 sensors for now, i want 6), but it will not work between sensors 1&3 or 2&4. See the attached diagram (sorry it a looks bad, but it was a 5 min job). In the diagram the same colours are common-ed. This lay out will take up two zones on the alarm panel. eg. of diagram - if 1 and 2 is triggered then green/purple will close, causing the alarm be activated: Red commons 1 and 2 creating a loop therefore making the green/purple N/C.

 

[KMoffett]

This is an analog comparator level detector. It has 6 inputs, but you can have more or less. The sensors are set for 12V-output on detect. RA thru RX, and R1 form a voltage divider. The detection level is set by R2. R2 is set for 7.0V on U1's pin 3. The voltage on pin 2 depends on the number of sensors triggered and supplying 12V. U1's output depends whether the voltage on pin 2 is high or lower than the voltage on pin 3.
0 sensors = 0.0V
1 sensor = 6.0V
2 sensors = 8.0V
3 sensors = 9.0V
4 sensors = 9.6V
And so on.
Any time the voltage at pin 2 is higher than 7.0V the output of U1 goes to 12V.

Ken

 

[Peet_Skeet]

Thanks Dude
This looks like it can work, as soon as i got it going i'll let you know.

 

[ChosunOne]

Critical question here: How long does the sensor relay stay activated when the sensor is tripped? Typical alarm industry motion sensor relays open/close for about 2 seconds. You may need additional circuitry to extend that time period so that a trip is caused by any two sensors within, e.g., 5 seconds. Two seconds might let moving objects get past unless there's a lot of overlap between all sensor fields.

Just guessing here in the absense of data, but I wanted to point it out. It's one of the parameters in cross-zoning.

 

[Peet_Skeet]

I can get a couple of timer boards from work that should work here. They can be set for 35 seconds.