I ended up removing the internal resistor and using two external resistors to hold it down to ground so the input didn't float. Also note that the motion is OPEN when there motion is detected (which makes sense, right?). Here is a schematic for something else I am working on, but shows how I attached a motion and a door contact (among other things) to the GPIO of a Pi. Please also note that the Aurora is being replaced, however, the new Honeywell version will likely be indistinguishably different from the installers perspective.
Add motion detection to your project using an off the shelf security system motion detector!
This example is not limited to just the Raspberry Pi, will also work with your 5V projects (recommend 4.7K resistor instead if you do this).
This motion detector is a quality component used for
security system installations, this ‘Aurora’ model is made by Honeywell/Ademco
and can be found new in the $15-25 range.
These hardwired models age well if you're considering re-purposing one; this one has been around for well over ten years and still works great. Bosch has a slick looking model too. Worth noting, you can see inside attached to one of the signal lines is a 1/2 watt resistor, (200 ohm I believe for that panel) - these are used to produce current so that the security panel can see if there is trouble, or if someone tries to short the wires out along the line it will detect the tamper.
its operating characteristics as
8-16VDC with a form A SPST 90mA @16VDC relay. I used a 12VDC power supply to play with this. If you are using a Pi or an Arduino, you will need access to that 8-16VDC to power it. I performed measurements on both the power input as well as the relay signal contacts.
On 12VDC supply lines:
No motion current: 3.82mA
Motion current: 9.38mA
Resistance on relay contact terminals:
No motion: 16 ohms
Motion: Infinite
Relay is closed while unit is powered and no motion detected, it opens if no power is present, or if motion is detected.
If you choose to disable the internal LED I would imagine you could shave off a few more mA if you're concerned about consumption.
To
make the motion suitable for our Raspberry Pi, I attached a ¼ watt resistor
with a value of 3.3K ohms onto the relay terminals; The current used by this
device will now use <= 1mA with the 3.3V supply voltage of the pi, which
will be suitable for our demonstration.
This picture to the right is with the new wire installed, which I used 22/4 station wire (standard for telephones and security systems). I also attached the new resistor inside the motion detector, which could just as easily be placed outside on a breadboard, a perf board....
When
3.3VDC was applied to the contact wires it measured 1.01mA when closed & 0
mA when open.
From left to right I used the scheme of red for +12V, black for ground, green is one side of the relay contacts, and yellow connects to the other side of the contact (this has the resistor attached between the yellow wire and the screw terminal - I used a 'b connector' to connect it, which is common in security and telecom). It doesn't matter how you connect the green and yellow to your project board, as the circuit is either open or closed with a current limiting resistor in there - connect one two the Pi's ground, and one to your I/O pin which is configured as an input.
The only other thing I feel I should mention is that since we're using 22 gauge wire at 3.3V, the length of the wire should be fairly short, or local to the project board. If you wish to run it 20-50' away, I'd strongly recommend using the 12V line for the signal and using an opto-coupler or a transistor or something like that to achieve your low current low voltage signal to your controller.
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