I'm in the process of using the Particle Photon + Relay Shield to bring an 15 year old home security system into the cloud.
Rather than replacing the alarm control board, I want the Particle to be able to sense:
- when the siren has been triggered (12V is fed to the siren)
- when the system is armed (a 12V output is available to trigger a relay
The some of the relays on the shield will be used to:
- Arm the old alarm system (which is done by closing the circuit on one of the zones)
- Control a ventilation fan
The old alarm is providing a 12V supply (with a battery backup) which is handy.
The relay shield does allow for external 5V to trigger the relays by cutting a track... and I'd thought that by doing that the relay contacts could be connected to the Photon digital inputs. Could I
Alternatively I'm reading up on using opto-isolators?
Maybe I could use transistors instead of relays?
...but my electrical skills are not