Alarm Contact

[Luciano]

Hi,

Darrel's schematic:

The components R1 and S1 are grouped into a dotted-line box,
corresponding to a physical unit. (R1 is inside an enclosure with S1).

* * *

It dosen't matter on which contact of the switch S1 the resistor R1 is soldered.

The system is secure only if the switch S1 and the resistor R1 are
in the same enclosure and coated with resin. (One physical unit).

If you put more than one switch in series on the same line, the system won't be secure.

Not secure system

+5 --R2--┐
         |
AN0 -----┴-----------S1--------S2-------S3---------S4R1--┐ 
                                                         |                                                 
GND -----------------------------------------------------┘ 


Secure system

+5 --R2--┐
         |
AN0 -----┴-----------------------------------------S1R1--┐ 
                                                         |                                                 
GND -----------------------------------------------------┘

(R2 is inside the microcontroller enclosure).

Best regards,

Luciano