Relays / Mosfets

[alarm_guy1]

Hi currently using a couple of relays to between my alarm system and my Pi, so basically when the Pir or door sensor activates the relay is triggeredfrom an output on my alarm system.

Unfortunately the relays are surprisingly loud especially when in the kitchen as the device activates multiple times if there are multiple people in there, I know I could box them to muffle it etc etc etc.

But is there a Mosfet circuit I can use to achieve the same goal?

my alarm panel puts out a 12Vdc signal, hence the current use of relays

cheers

[rpdom]

Using a MOSFET to connect your alarm system to the Pi may cause problems because of the voltage difference. Ideally you want to keep the two circuits electrically isolated from each other.

An alternative may be to use opto isolators with the Input coupled to the alarm system via a suitable resistor and the output connected to the Pi's GPIO also with suitable resistors.

[alarm_guy1]

Cheers,

I'll take a look.
Thanks for taking the time to reply

[Ilfirin]

+1 for optoisolator. Simplest, safest and widely used on industrial boards for digital inputs, even 230AC ones.

[alarm_guy1]

Cheers guys,

taken a punt with 3 of these boards https://www.ebay.co.uk/itm/202091702337

we will know by Xmas

[Ilfirin]

That's pretty nice solution

[alarm_guy1]

I'll post back when it turns up

But it will be 2 month before I get it