I have a house alarm which will apply 12v to an output when an intrusion is detected. I'm looking for a simple device that will take this 12v as an input to trigger an event which I can then use IFTTT to do something else, such as turn on my Philips Hue lights for example. Has anyone any experience of devices that can take a 12v input as a trigger and then fire an event to IFTTT? I'd appreciate any recommendations or guidance on implementing something like this.
All you need is 2 Resistors and then any microcontroller with a 3.3v GPIO input pin (e.g. ESP8266)
You need to build a voltage divider, the equations on that page will help you work out what the ratio of the 2 resistor values needs to be (But something like 20 kohm and 7.5 kohm should be in the right ball park). You can also use this calculator to do the maths for you.
When the pin goes high, you get that information with the microcontroller and then you can make a HTTP request to IFTTT that triggers your action.