LTR390 UV and Ambient Light Sensor

The ltr390 sensor platform allows you to use your LTR390 UV and ambient light sensor (datasheet, Adafruit) with ESPHome.

The I²C Bus is required to be set up in your configuration for this sensor to work.

../../_images/ltr390-full.jpg
sensor:
  - platform: ltr390
    uvi:
      name: "UV Index"
    light:
      name: "Light"

Configuration variables:

  • uv_index (Optional): UV index (UVI). All options from Sensor.

  • uv (Optional): Sensor counts for the UV sensor (#). All options from Sensor.

  • light (Optional): Lux of ambient light (lx). All options from Sensor.

  • ambient_light (Optional): Sensor counts for the Ambient light sensor (#). All options from Sensor.

  • gain (Optional, string): Adjusts the sensitivity of the sensor. A larger value means higher sensitivity. See table below for details. Default is "X3".

  • resolution (Optional, int): ADC resolution. Higher resolutions require longer sensor integration times. See table below for details. Default is 18.

  • window_correction_factor (Optional, float): Window correction factor. Use larger values when using under tinted windows. Default is 1.0, must be >= 1.0.

  • address (Optional, int): Manually specify the I²C address of the sensor. Default is 0x53.

  • update_interval (Optional, Time): The interval to check the sensor. Defaults to 60s. It is recommended that the update interval is at least 1 second since updates can take up to 800ms when using a high resolution value.

Lux and UVI Formulas

\[\text{lux} = \frac{0.6 \times \text{als}}{\text{gain} \times \text{int}} \times \text{wfac}\]
\[\text{UVI} = \frac{\text{uv}}{\text{sensitivity}} \times \text{wfac}\]

where:

  • als and uv are the sensor values

  • gain is the amount of gain, see the table below for details

  • int is the integration time in 100s of ms and is tied to the resolution, see the table below for details

  • sensitivity has the value 2300 and is the sensor’s count per UVI

  • wfac is the window correction factor

Gain

Gain Parameter

gain

X1

1

X3

3

X6

6

X9

9

X18

18

Resolution

Resolution

Resolution Parameter (bits)

Integration Time (ms)

int

16

25

0.25

17

50

0.5

18

100

1

19

200

2

20

400

4

See Also