Use of old (90s) wired motion sensors?

Hardware Home Automation
1

Hi
I currently have a really small openHAB 2 installation, with just a couple of power switches and a Fibaro multisensor, running on a RPi3.
In my house I also have an old installation of an alarm system, with four wired motion sensors placed at good covering positions.
Would it be possible to use these with my RPi and openHAB? Anyone here that have done the same?
I realize that I haven’t told you the exact specs for the sensors (I don’t know yet), but maybe someone have done it before, or possibly someone know for a fact that it would require more money/work than just buying a couple of more multisensors for about €50 each?

/Olof

2

If the output of a sensor is a relay then you should be fine. You can connect them to the I/O ports of the RPI (you’ll need a pull-up resistor on each line).
You may need some passive filtering too if the motion detectors are a long way away as they’ll be noise on the line which, without the filtering, could trigger false values.

3

I would do that with an arduino. Cheaper to replace if you burn out the gpios. and then forward to the pi with mqtt or the serial binding.

4

See also: How to connect generic PIRs to OpenHAB?
Also check the Fibaro Universal Binary sensor, that is what I’m using for my (old) alarm system.

5

All my own stuff like that is done with Arduinos and MQTT. I wasn’t sure what the OPs knowledge was of such things. To ask the question in the first place suggests limited rather than extensive.

6

My old PIR has an internal relais that directly switches a 230V current. So I ordered another relais which supports 230V on the coil side and used it to switch the contact of a HomeMatic wireless contact sensor. This can be adapted to any kind of device with input pins at low voltage level.

7

Thanks!
At least is seems like it could be possible.
I’ll continue with investigating exactly what kind of sensors I have, and try to locate info about them.

Regarding my knowledge, yes definitely limited.
I’m more of a computer (software) guy, so I’m not all that familiar with the powering of sensors or the connections to the GPIO on the RPi/Arduino.
I’m interested in learning though, so just to know that it might be possible is enough to dig deeper into it once the summer heat leaves and let me work in indoor projects.

/Olof

8

Sure it can be done, and connecting to GPIO is basically for free (if your Pi is where your alarm system cables meet). Think, though, what you will want to achieve long-term and what’s the sensors you will need for this. I’ve also got Fibaro multisensors, and I use motion, temp and luminance sensors in each of them (temperature for heating control, luminance for shading and auto-adapted lighting). Which is what you cannot get from your PIRs.
In “wet” rooms I’m also using the Aeotec multisensor which in addition has a humidity sensor, to control ventilation.

You could use your alarm cables to get 5VDC delivered from a central power supply to the Fibaro or Aeotec sensors so they don’t need to run on battery. That’s something I’m in the process of migrating my Fibaros to, too. Which is a lot harder to accomplish since I don’t have those alarm system cables in place.