Elgato Key Light Series

Temperature Control

The Elgato Key Light uses mireds (micro reciprocal degrees) for temperature control. Mireds are a unit of measurement used to express color temperature, calculated as:

mireds = 1,000,000 / Kelvin

The device accepts values in the range:

• 344 mireds (2900K, warm) to 143 mireds (7000K, cool)

Temperature Conversion Table

Kelvin	Mireds	Description
2900K	344	Warm (incandescent)
3900K	256	Warm white
4950K	202	Neutral
5950K	168	Cool white
7000K	143	Cool (daylight)

When setting the temperature through the keylightd API:

1. The input Kelvin value is clamped to the valid range (2900K-7000K)
2. The clamped Kelvin value is converted to mireds using the formula above
3. The resulting mireds value is sent to the device

For example:

• Setting 2000K → clamped to 2900K → 1,000,000/2900 = 344 mireds
• Setting 8000K → clamped to 7000K → 1,000,000/7000 = 143 mireds

Brightness Control

The brightness is controlled as a percentage:

• Range: 0-100%
• Values below 0% are clamped to 0%
• Values above 100% are clamped to 100%

Power Control

The power state is controlled as a boolean:

• true = On
• false = Off

API Endpoints

The device exposes the following HTTP endpoints:

• GET /elgato/accessory-info - Get device information
• GET /elgato/lights - Get current light state
• PUT /elgato/lights - Set light state

Accessory Info Format

{
  "productName": "Elgato Key Light",
  "hardwareBoardType": 53,
  "hardwareRevision": "1",
  "macAddress": "XX:XX:XX:XX:XX:XX",
  "firmwareBuildNumber": 222,
  "firmwareVersion": "1.0.3",
  "serialNumber": "CNXXXXXXXXXX",
  "displayName": "Elgato Key Light XXXX",
  "features": ["lights"],
  "wifi-info": {
    "ssid": "YourNetwork",
    "frequencyMHz": 2400,
    "rssi": -41
  }
}

Light State Format

{
  "numberOfLights": 1,
  "lights": [
    {
      "on": 1,           // 1 = on, 0 = off
      "brightness": 60,  // 0-100
      "temperature": 344 // 143-344 mireds
    }
  ]
}