Homeassistant MQTT Light

Homeassistant compatible MQTT Light implementation for RGB+CCT LEDs. Uses ESP8266 and PCA9685.

The idea started because I wanted "white with a color tint" smart lights. But apparently, this is not supported by smart home tech yet. It's either RGB, or white, never a mix of these. So this lamp here identifies as RGB, but mixes white with it.

Color mixing

To mix colors, the lamp takes the minimum of the three R,G,B colors, and replaces it with white.

• RGB(255,255,255) --> RGBW(0,0,0,255)
• RGB(255,128,0) --> RGBW(255,128,0,0)
• RGB(255,192,128) --> RGBW(128,64,0,128)

White mixing

In addition, this lamp supports tuneable white, so mixing warm white and cold white with everything else. In order to make Homeassistant use this, the lamp remembers the last color temperature setting and uses this.

• RGB(255,255,255),TEMP(255) --> RGBWC(0,0,0,0,255)
• RGB(255,255,255),TEMP(0) --> RGBWC(0,0,0,255,0)
• RGB(255,128,0),TEMP(255) --> RGBWC(255,128,0,0,0)
• RGB(255,192,128),TEMP(64) --> RGBWC(128,64,0,192,64)

Invisible color temperature updates

Most smart lamps only let you update the color temperature while they are on. So they turn on with the previous color temperature and then dim to the right one. To combat this behavior, send a message with brightness=1 and the desired color temperature to do an invisible update. The lamp will remain in its previous state (OFF, that is). Such low brightness values usually are not showing in most lamps, either.

Homeassistant integration

The lamp supports autodiscovery and identifies as "ESP-dimmer-NUMBER", where the number is derived from the MAC address. Supported features:

• JSON schema
• ON/OFF
• brightness
• color temperature
• RGB
• transitions
• flashing

Effects

The lamp supports the following effects:

• Colorwheel - slowly changes through the RGB spectrum
• Undulation - slowly undulates randomly near the previously selected color

Stand-alone mode

As a fallback, the lamp supports stand-alone operation:

• On powerup, the lamp turns on with neutral white

Hardware

The lamp uses the PCA9685 PWM driver IC (16 channels, 12 bits, up to 1.5kHz, I2C) to interface with the LEDs. Currently, channels 1..5 are assigned R,G,B,WW,CW.

Ledcontroller_3x

This PCB includes the ESP8266, PCA9685 and BLM3400 mosfets, for controlling 24V LED strips with a common +24V.