The London Underground Philips Hue Light Switch
A decommissioned Jubilee Line door button turned in to a Philips Hue light switch, complete with Sonos integration for a little bit of disco.
I picked up a decommissioned Jubilee line door button after a trip to the London Transport museum. Given my addiction to Hue lights, a switch was the obvious thing to do with it.
There wasn't much information on repurposing the door button, so I created an Instructable "Hacking a London Underground Jubilee Line Door Button".
I had a few options to control the lights: an ESP8266 / ESP32 Arduino to talk to the Hue API, a DIY Zigbee light link device such as described on PeeVeeOne, or taking apart a Hue Switch and modifying it to work with one button by the use of a microcontroller (although Philips have since released this).
I went down the ESP32 route as it would also let me integrate with the Sonos API to create a secret disco mode. If I get around to putting the ESP32 into sleep mode then the battery should last a decent amount of time, although for some reason my ESP32 refuses to be powered by my 3.7V lipo battery so I am currently running it off of USB.
The code for the ESP32 is on github, with the code for the Sonos integration in its own branch.
One of the tricky parts of the project was the Sonos integration, I've created a small app to ease the generation of Sonos auth tokens for Microcontroller projects.