elgato.dart

A tool to interact with Elgato Lights.

What?

Let's face it, in 2020 when a ton of us are working from home, many of us have expanded our home workspaces - and in some cases, have added better lighting.

I purchased an Elgato Key Light Air which is an excellent source of light. I spend a non-trivial amount of time on video calls for work and for personal life now, and oftentimes have breaks between calls during which I don't want the light on.

I looked for a way to control the light's on/off behavior from my command line, and didn't seem to find one, so I built one.

Why?

The light itself has a physical power on/off switch on the back of the device, which can be a little tricky to reach if you're placing the light right above a monitor. Also, when flipped on, it lights up to its most powerful setting briefly, and then settles back to whatever configured setting I had it before I powered it down.

Elgato provides a couple of interfaces - one is the macOS Control Center, and they provide Android and iOS apps, but I don't want to have pull my phone out every time I want to turn the lights on and off, and the desktop interface is two clicks, and I'm lazy.

There's also the Elgato Stream Deck controllers, but even at the smallest size it costs about $80USD, and I didn't want to spend that much on a light switch. If I was controlling more things, then it is probably an excellent choice, and many people use them.

How?

This project is written in Dart, and can probably be compiled on any platform that Dart supports (Windows, Linux, macOS) - I have macOS, so I've only tested it against that platform.

There's an open issue on Dart about code signing, so downloading compiled binaries wasn't something I pursued yet.

Instead, if you want to use this, follow these steps.

(macOS steps only for now)

# Install dart sdk
brew install dart-lang/homebrew-dart/dart
# Clone this repo 
git clone https://github.com/miketheman/elgato.dart.git
# Enter the directory
cd elgato.dart
# Compile to native code:
dart compile exe elgato.dart
# Execute the resulting binary
./elgato.exe

You can control the desired output binary py passing -o <output filename> to dart compile. To place the binary somewhere in your $PATH, such as /usr/local/bin for simpler execution, use this command:

dart compile exe -o /usr/local/bin/elgato elgato.dart

And then you should be able to execute the program from anywhere via elgato.

Hooray! 🎉

Who?

This project was inspired by Brett Langdon, who had figured out how to do this in a simpler, bash-friendly approach, while assigning a static IP address to the light, curl, and jq, something like this:

#!/usr/bin/env bash
curl -qs http://192.168.1.10:9123/elgato/lights \
  | jq -c '{numberOfLights, lights:[.lights[] | {on: (if .on == 1 then 0 else 1 end), brightness, temperature}]}' \
  | curl -X PUT -d @- -H "Content-Type: application/json" http://192.168.1.10:9123/elgato/lights

Mike Fiedler took this idea further and wrote a single, self-contained binary application in Dart that can discover lights on the network.

Both approaches work, so you can choose your own adventure!

I wrote this since I don't statically assign IPs on my network, to learn a little more about Dart, and because it was fun!

What Else?

(a collection of ideas that could improve this)

• I'm not a professional Dart developer - it's entirely possible there's better implementations or ways to structure the code - assistance is welcome! Including tests! 😁
• At some point, this could be expanded to interact with other Elgato products, but starting with the only one I have right now - the [Key Light Air].
• There's no current option to remove the cache file if the IP changes, so removing $HOME_FOLDER/.elgato.dart.cache and re-running the tool will discover the IP of the light again and cache it. The cache is used to speed up subsequent invocations, since discovering an mDNS address can take a few seconds.
• I can imagine considering using DNS names instead of IP addresses, especially in a multi-light household where you wouldn't want one command to switch all lights, so setting up the lights to have a common string in their name might be smarter, and that could be set as a configuration value (no config file exists yet).
• Anything else you can imagine, since we're software developers and make ideas come to life with technology!