Feasability - 12V relay and wemos d1 mini to signal alarm state?

Hi all,

First project I am attempting so please be kind :sweat_smile: I am attaching a very basic schematic showing what I would like to do.

Basically, when my house alarm goes off there is a terminal which goes to 0V. Using this an a permanent 12V terminal I could use the alarm state to activate a 12V relay. Maybe something like this?

Then the output terminal of the relay could be used as an input to a terminal of a wemos d1 mini or equivalent device like this maybe? Which then sends me a notification on my phone. Finally I could use IFTTT to switch on my external sonos controlled security lights.

I’m wondering if there is a combined relay/wemos type device, but as you can see the logic is backwards to the normal “wemos controls relay which controls a power circuit”. I am going with “alarm controls relay which signals wemos to notify me of alarm”.

I’m in the UK so looking at Amazon firstly for any parts, so I can tinker with it over Xmas break.
Would appreciate any advice on hardware/other solutions.

What you are proposing with a relay is fine and gives you some isolation from the alarm , which is a bonus.

Use the relay contact with a pull up resistor as a digital input . Detect that in your code to initiate your call.
If this is is your first project , I’d buy a genuine Arduino ( there are cheaper alternatives , but as a as a starter its s a good move ) and get that working with your alarm( turn on a led for example) , then look at getting suitable shield for sending a txt or whatever you decide to do .
You’ll need a few bits to try this , such as a breadboard, few bits of wire, led, few resistors ( 10k and 270R).

Look at the digital input /output examples in the IDE

hammy:
What you are proposing with a relay is fine and gives you some isolation from the alarm , which is a bonus.

Use the relay contact with a pull up resistor as a digital input . Detect that in your code to initiate your call.
If this is is your first project , I’d buy a genuine Arduino ( there are cheaper alternatives , but as a as a starter its s a good move ) and get that working with your alarm( turn on a led for example) , then look at getting suitable shield for sending a txt or whatever you decide to do .
You’ll need a few bits to try this , such as a breadboard, few bits of wire, led, few resistors ( 10k and 270R).

Look at the digital input /output examples in the IDE

Thank you @hammy for the quick reply!

Glad I am heading in the right direction at least. Pull up resistor connected something like the attached diagram? I’m wondering what the normal Vcc supply if fed from.

I was looking at the Wemo D1 mini which has wifi built in, so no need for a shield then?

I will have a look for the examples you mentioned. Lots to learn but I like a challenge! :slight_smile: