How to connect two sensors to single zone - alarm system

Today we are going to show you how to connect two sensors to single zone for hardwired alarm system. Since almost hardwired sensors utilize "Normal Close" output, we will use this method in below connection.

You have noticed the above photo, that's an example what the connection is. In above picture, the alarm panel is 16 hardwired zones hardwired alarm panel (Model: GSM800-16), and two hardwired PIR motion sensors (Model: VS-YH500).

Two PIR sensors wiring (tamper switch connection)

We use four color wires for this connection, including red (+12 power), black (GND, Zone -), green (Zone +), white (connection wires between two sensors). Red and black wires to connect power supply, and green color wire should connect to zone +. Because we need to use the tamper switch, we connect the tamper switch to alarm output in series (yellow cable). Have you noticed the Resistor? That's very important for hardwired connection of hardwired alarm system. This resistor has a special name - EOL resistor, it can protect your wiring from being deliberately damaged by intruders.

Two PIR sensors wiring (No tamper switch connection)

Typically, PIR motion sensors installed in minimum 2.0 meters height, and you may don't want to connect the tamper switch. This is a simple connection, it only uses the alarm output of hardwired motion sensor. Certainly, if your alarm panel supports separate tamper protection, then can simply use extra two wires make the connection. Red and black color wires are for power connection, green color wire is for zone +, two sensor was connected with one yellow wire.

After you finished the wiring, you can connect them to one hardwired zone of alarm panel. If you have chosen the first connection method (with tamper switch), making sure to put the sensor's cover back. When you encounter problems, you can use the Multi-meter to measure resistance of the green color and black color (Zone +, GND), the value must be close to 2.2K.

Two sensors connect to DVR/IP Camera

Professional DVR and IP cameras have alarm input/output interface. You can connect hardwired motion sensor to alarm input of these security equipment. The connection method is as same like alarm panel's connection, but you don't need use the EOL resistor. You can check below photo to see how to connect two hardwired sensors to DVR.

EOL (End of line) resistor

Why it is important to place them at the EOL or End of line. We also look at alarm basic circuits. The EOL allows the control panel to supervise the field wiring for open or short circuit.

EOL resistor placed at the last device of a loop (circuit) allows supervision of the loop. The panel is looking for (e.g.) 2K Ohms instead of near-zero ohms. This is to prevent loop short circuits from bypassing sensors in the loop. Stripping and shorting loop wires in a loop that doesn't use EOLR's is one way to circumvent the alarm. More common is wires being pinched by grounded metal or moisture somewhere in the circuit, and short-circuiting the sensors through grounding points.