Introduction
For hydroponics systems, every plant has preferences on how long they want sunlight per day. Some are 12 hours and others are 8 hours. This time, we would like to measure UV-light, visible light, and infrared light and check the growth.
Seeed (a hardware company) provides a Grove – Sunlight sensor (weblink). So, I would like to show how this sunlight sensor can be developed with our hydroponics system.

Hardware Specification
This sunlight sensor comes with SI1145 from SiliconLabs. It is a reflectance-based infrared proximity, UV index, and ambient light sensor.
The interface with the hardware is I2C.

Software Guide
Platform IO has Grove – Sunlight Sensor library.

Useful Header file and APIs – Arduino IDE: File > Examples > Grove_Sunlight_Sensor>SI1145DEMO
- Header File
- SI114x.h
- Object Instantiation
- SI114X SI1145 = SI114X();
- APIs
- SI1145.Begin()
- SI1145.ReadVisible()
- SI1145.ReadIR()
- SI1145.ReadUV
- real_UV = ((float)SI1145.ReadUV() / 100 )
Lab Test
This sensor can output three information
- Visible Light
- Infrared (IR) Sensor
- UV light index: UV in mW per area
- 0 to 2: Low UV
- 3 to 5: Moderate
- 6 to 7: Hight
- 8 to 10: Very High
- 11 or more: Extreme

When just a room light is on,
When the hydroponic light is on,
Reference
Grove Sunlight Sensor wikipage: weblink