Hi. No you can't just connect 5V to your alarm panel from the pi, The alarm panel is designed to work at nominal 12V, so the pir sensors would not work at 5V, the door switches will have termination resistors again designed for 12V operation. To use the pir sensors you would need to provide 12V DC ...

I have an existing alarm system in my house that never worked since we moved in. I wanted to connect all the door sensors and 2 motion sensors to a RPI. To start, I grabbed one motion sensor, a PIR-700, which has 4 wires connected as follows (images attached): 1. Black - Port 5 2. Red - Port 6 3. Gr...