I’m just starting to dive into the Smart Home world. We recently bought a house built in 2006, which has old PIR sensors in each room and the garage. Now I want to replace the old sensors with Aqara FP2 sensors. The only problem is how to power them using the existing cables.
From the pictures, it seems that the PIRs used 12V 6Gang wire, while the Aqara FP2 requires 5V USB-C. On the main unit end, there seems to be an old converter or something similar. Is there a simpler plug and play method to get the 5V to the sensors using the old wires?
Trying to send 5V over long distance might not be the most reliable method, as you start with 5VDC, but you might end up with 4VDC or less.
The best way to get the Aqara going is to get VAC voltage to the location of the sensor and use a 5V transformer to supply voltage to the sensor.
Small format transformers (the size of 2 matchboxes) are available, using bare wire at both ends VAC and VDC. You can also use these transformers to send 5VDC over the present wiring for testing (check VDC drop is not substantial to, for example, not power up the sensor).
Since voltage drop is an issue over long distances as per what Habitats Tech has mentioned you could join three wires together for each of the power legs (positive and negative) to run to each FP2. Hopefully that would be enough to prevent any serious volt drop.
Then you could simply install a 5V dc power supply at the location of that old alarm panel to run all the FP2’s.
The other issue is then at the FP2 end where you would need to have a USB C plug on the end of the existing wires.
Are the cables twisted?
A power injektor for PoE might be a solution.
This would also mean you just need to fiddle with getting RJ45 connectors on each end of the existing cables.
