Offline Alexa Nurse Call Device (2nd Generation)

This document outlines the second-generation design for the offline Alexa nurse call system. This device requires no coding or soldering if following the steps listed below. This system allows Alexa to work offline to control most hospital call light systems that work off a 1/4" stereo plug input. For more information on how this system works, please refer to this blog post. 

Listed below are all the parts required (with links):

ZigBee Relay

¼” male to ¼” female mono stereo cable

Project box

12V power supply

 

Steps for assembling device:

Step 1: Take the ¼” male to ¼” female mono stereo cable and cut the wire to separate the male and female ends. It is best to cut the wire so the male end has 2/3^rds or more of total wire length (cut closer to the female end). Once the wire has been cut, strip the wires as shown in the figure below, so both the male and female ends have two bare wires each.

Step 2: Take the 12V power supply and cut the barrel jack off the end and strip the wires as shown in the image below.

Step 3: Drill two ~3/16" holes in the side of the project box on one end.

Step 4: Drill one ~5/32" hole on the opposite side of the project box.

Step 5: Pull the ¼” male stereo wire through one of the 3/16" holes in the project box and the ¼” female stereo wire through the other 3/16" hole. Pull the 12V power source wire through the 5/32" inch hole in the project box. Once the wires are pulled through, tie a knot in the end as shown in the image below to provide strain relief for the wires.

Step 5: Connect the 12V power supply stripped wires to the power input terminals on ZigBee relay. The V+ and V- inputs on the relay are labeled in the picture below (the V+ input is the terminal on the outer portion of the relay). If using the 12V power source provided in the link, the V+ wire is the wire with the striped, white lines, as labeled in the picture below.

Step 6: Connect the stripped wires from the ¼” male and ¼” female stereo cable to the COM and NO terminals on the ZigBee relay. Connect the two white wires from each of the stereo cables to the NO terminal and connect the two all-copper wires to the COM terminal. The COM and NO terminals are labeled in the image below. The COM terminal is located in the middle and the NO terminal is located near the outer edge of the relay.

Step 7: Once all of the parts are assembled as shown in the picture below, pair the device to Alexa by following these steps: 

    a) Plug the device into power

    b) The red light will start flashing on the ZigBee relay, indicating it is in pairing mode

    c) Tell your Alexa device with a built-in ZigBee hub to "Discover Devices"

    d) Once the device is discovered, the light on the ZigBee relay will turn solid red

    e) Go into the Alexa app and rename the device to "Nurse Call" (or similar name). 

    f) Press the "mode" button on the relay for 1 second (labeled in the image below) to put the relay in "momentary" mode and out of "toggle" mode. To test the relay to ensure that it is in "momentary" mode, push the trigger button (labeled in the image below) for 1 second. If the relay is in "momentary" mode, the relay will "click" on for 1 second and then click back off again. If the relay stays on, push the "mode" button again and repeat the steps above.  

    g) Once the relay is in the correct mode, screw on the top of the project box to complete the set up of the system. 

    h) If the relay needs to be reset (if needing to unpair from Alexa device and pair to new device), hold the trigger button (labeled in the image below) for 5 seconds. The light on the device will change colors and then the red light will begin to blink, indicating that it is back in pairing mode. 

Step 8: Once the device is paired to Alexa and in "momentary" mode, let the system sit connected to Wi-Fi for 24 hours. This will allow time for the device name to be loaded locally onto the Alexa device, to allow for local voice control to work for the call light system. Once it has be connected for 24 hours, the system can be moved off Wi-Fi and set up in a hospital room (this should be far away from where the system was connected to Wi-Fi originally). 

Step 9: To connect the device in a hospital room, plug the 1/4" male stereo jack into the call light system, plug the manual call light system (e.g. sip-and-puff or tent switch) into the 1/4" female jack to allow for a manually call light option, and then plug the device into power. It is best to secure the device to the wall near the call light system and label the system to let staff know not to unplug it from the wall. 

Step 10: The system can now be used offline to control the call light system. The person simply says "Alexa, turn on nurse call" and the call light system can be triggered by voice. The person can also trigger the call light manually, if there is a manual nurse call system plugged into the device.