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Friday, 19 January 2018

Home Automation System - Alarm and OpenHAB...my idea

I can't believe it!!! I reached a little goal...Home Alarm and OpenHAB together...

I know...It seems a simple thing...today home alarm systems can be remote controlled ... but the old ones (as mine is...) don't...

My target was to view the input status of all sensors / radars in my home alarm system...I don't like remote controller...just remote monitoring...

So, it's quite simple: I have to integrate all sensors / radars with a device, as Arduino or similar ones, and gets the input status (OPEN / CLOSE).

I have to know what kind of signal is transmitted by sensors / radars...I discovered the wires from the sensors / radar and with the tester I found the voltage is about 4.5v when the signal is HIGH and 0 when the signal is low.

I made some test with my main entrance door so I confirmed this behaviuor. Door OPEN, 4.5v on the terminal...DOOR closed, 0 voltage.

Now, I have to find a device with at least 11 GPIO 4.5v tolerant

I can choose between:

- a NodeMCU ESP8266 device, with integrated wifi; but it accepts only 4 volts

- an Arduino UNO with ethernet shield, with GPIO 5v tolerant;

The first choice would be the best, because we have integrated wifi and a very small layout...but I have to step down voltage from 4.5v to 3.3v (max)

Otherwise, using Arduino UNO, the voltage is already OK but I need a new shield (ethernet shield)


Raspberry PI3 where OpenHAB and MQTT broker are running, has a lot of GPIO on its board. I could use them. But these GPIO works with 3.3v max. No problem...I will build an interface device with voltage divider...

Then I could use an OpenHAB bindings (see https://github.com/openhab/openhab1-addons/wiki/GPIO-Binding) to manage GPIO, so no needs for an external software...


 - take all alarm input wires to the Raspberry PI3
 - build an interface to step down voltage from 4.5v to 3.3v
 - download and setup of GPIO binding of OpenHAB (see https://github.com/openhab/openhab1-addons/wiki/GPIO-Binding)
 - make a new sitemap to see the alarm device input

In the next post, I will descrive the operational phase of work

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