I wanted an easy way to detect when my (medically complex) son was in his bed so that I could trigger other smarthome rules from his presence. This Instructable shows how I followed the process documented by some other users on the Samsung SmartThings forums to create a Z-wave pressure mat to use as an "in bed" detector. Cheers!

Jonathan Lasko
maxstrength.org

Step 1: What You'll Need

To build this Z-wave connected pressure mat, you'll need:

a Z-wave open/close sensor with leads allowing you to connect your own switch (I used an Ecolink DWZWAVE2-ECO, $29 on Amazon.)
an easily-modifiable pressure mat (I used an Ideal Security SK630 Pressure Mat, $22 on Amazon.)

Many of these pressure mats are weather-proof. It is definitely a good idea to get a waterproof may if you are planning to use this in the bed of a child, eldery loved one, or someone with complex medical needs.

Step 2: Test the Individual Components

Before you modify the pressure mat, it's good to make sure it works as expected. Try connecting the cord of the mat to the alarm and testing that you hear the chime.

This way, if it seems like the mat is broken, you can still send it back. (In subsequent steps, we'll modify the mat, which might make a return more difficult.)

Similarly, now would be a good time to test your open/close sensor to make sure it is working. Connect it to your hub of choice. (I use Samsung SmartThings.)

Step 3: Expose Pressure Mat Bare Wires

There are two option for our approach:

Approach #1: Fellow Instructabler tachyon offered this bit of wisdom: "I always try and avoid cutting off connectors whenever possible and feasible. Instead buy the corresponding mating connector and attach some wires to that. This way if you ever want to sell, repurpose, or return a device to its original use you'll have the ability to do so easily. Plus you'll have the advantage of a connector so you can easily unplug the device for transport, repair, testing, etc."

I heartily agree with tachyon, and while I don't currently know exactly which part to purchase to serve as the receiving/female end to that output, I will post it later if/when I find out.

Approach #2 (this is the one I took): Cut the plug off the end of the pressure mat cord, removing some insulation in order to expose sufficient wire to connect inside the open/close sensor.

Step 4: Connect the Pressure Mat to the Open/close Sensor

Open up the open/close sensor. As long as you bought an open/close sensor which allows you to hook in your own switch, you should see a space to connect the bare wires, similar to what is shown. Connect the wires from the pressure mat. At this point you should be able to test that the mat is properly connected to the open/close sensor by putting pressure on it. (The sensor should indicate via LED light that it is opening/closing.)

Step 5: Test the Final Result

Time to test your Z-wave connected pressure mat! You can see in the video that when I step on the mat, the Samsung SmartThings app indicates that the sensor is reporting closed. When I lift my foot, it reports open again.

I put this in my (medically complex) son's bed, where I use it in smarthome rules like:

turning off our home stereo system automatically when my son goes to bed
blink lights in another room if my son is in bed and his heart rate monitor (see https://github.com/yahnatan/pulseox) indicates that he might need assistance