Fan-Light-as-a-Service

A minimal ASP.NET Core Web API that controls a dimmable LED connected to a motherboard fan header via LibreHardwareMonitor. Runs as a Windows Service and integrates with Home Assistant via MQTT Discovery.

Setup

1. Connect a dimmable LED to a fan header on your motherboard.

2. Identify the sensor name using Fan Control, or run:

   dotnet run -- --list-sensors

3. Set the sensor name in appsettings.json:

   {
     "SensorName": "AIO Pump"
   }

4. Run (requires administrator privileges for hardware control):

   dotnet run

Home Assistant Integration

flaas uses MQTT with Home Assistant Discovery. When configured, the light entity appears automatically in Home Assistant -- no manual HA configuration needed.

Add the MQTT section to appsettings.json:

{
  "SensorName": "AIO Pump",
  "HardwareMin": 55,
  "HardwareMax": 100,
  "Mqtt": {
    "Host": "your-mqtt-broker",
    "Port": 1883,
    "Tls": false,
    "Username": "",
    "Password": "",
    "TopicPrefix": "flaas",
    "DeviceName": "Fan Light"
  }
}

The MQTT bridge will:

• Publish a discovery config so HA auto-creates a dimmable light entity
• Publish state and brightness changes in real time
• Accept on/off and brightness commands from HA
• Re-announce when HA restarts (via the homeassistant/status birth message)
• Report availability (online/offline) including on unexpected disconnects via MQTT LWT

HardwareMin and HardwareMax map the 1-100% brightness range to your hardware's actual usable range. For example, if your LED is off below 55%, set HardwareMin to 55. Both are optional and default to 1/100.

Set Mqtt:Tls to true to connect via TLS (port defaults to 8883). Works with the HA Mosquitto add-on's TLS listener and Let's Encrypt certs.

Leave Mqtt:Host empty to disable MQTT and use only the REST API.

Security

API key — Set ApiKey in appsettings.json to require an X-Api-Key header on all POST requests. GET endpoints (state, UI, health) remain open. Access the UI with the key via /ui?key=YOUR_KEY.

Listen address — Set ListenUrl to control the bind address (default http://*:5112). Use http://localhost:5112 to restrict to loopback when only MQTT control is needed.

MQTT TLS — Set Mqtt:Tls to true to encrypt the broker connection. Port defaults to 8883 when TLS is enabled.

Build & Deploy

dotnet build
dotnet run                          # runs on http://localhost:5112 (configurable via ListenUrl)
dotnet publish -c Release -o C:\flaas  # deploy to service directory

Note: appsettings.json is excluded from publish output to avoid overwriting production config. Target: .NET 10.0, win-x64 only.

Install as Windows Service

# From the publish directory, run as admin:
.\install.ps1

The installer will prompt you to select a sensor if SensorName is not already configured.

The service account defaults to LocalSystem since the service needs admin access to control fan hardware via LibreHardwareMonitor. Override with -Account if needed.

Manage the service with:

sc start flaas
sc stop flaas

REST API

A web UI is available at /ui. The following endpoints are also available:

Method	Path	Body	Description
GET	/health	--	Health check (200 OK)
GET	/	--	Current state
POST	/	{"isOn": bool, "brightness": N}	Set full state
POST	/on	--	Turn on
POST	/off	--	Turn off
POST	/brightness	{"brightness": N}	Set brightness (1-100)