Commercially available alarm systems connect to their devices using a 4 core or 6 core alarm cable. In the previous chapter, we used a 4 core cable because we were connecting a switch that needed two wires plus an antitamper loop, which needed another two wires.
For our PIR sensor circuit, we need the same four wires; however, we also need to send power to the device from the control panel, so an additional two wires are needed for this—hence the requirement for a 6 core cable.
The following diagram shows the wiring connections for my GardScan PIR sensor, but this is in fact typical for most off-the-shelf security system devices:
Typical connections for security system sensor devices
Similar to the magnetic contact sensors that we looked at in the previous chapter, devices can come with either a normally closed (NC) or a normally open (NO) alarm. This particular device has a normally closed output, which means that the alarm circuit will be broken when the detector...
