Grove SI1145 Sunlight, IR and UV I2C Sensor

The Grove Sunlight and UV I2C sensor can monitor sunlight intensity, IR intensity and UV intensity. All in one sensor. The sensor is a multi-channel digital light sensor, which has the ability to detect UV-light, visible light and infrared light.

NOTE:  We have now moved the Grove Connector to the back to make it easier to mount

This device is based on SI1145, a new sensor from SiLabs. The Si1145 is a low-power, reflectance-based, infrared proximity, UV index and ambient light sensor with I2C digital interface and programmable-event interrupt output. This device offers excellent performance under a wide dynamic range and a variety of light sources including direct sunlight.

The board contains an I2C Grove Connector ready to plug into your Pi or Arduino

UV Transparent Fused Quartz Window Available

If you are putting a Grove Sunlight / IR / UV sensor in a weather proof container, you should use a far-UV transparent Silica Quartz plate for the window over the sensor.

However, remember most plastics and glass are basically impervious to UV radiation (that’s why your Photogray sun glasses don’t work well in a car) so you need to use a special plastic or what I prefer, Silica Quartz. These Quartz JGS1 windows will let the UV through.

https://store.switchdoc.com/double-side-polished-far-uv-fused-silica-quartz-glass-sheets-plate-30-30-1mm/

Downloads

• Raspberry Pi Software (from SwitchDoc Labs)
• Arduino Software (from SeedStudio)
• SI1145 Full Specification

Example Project Software

• SunIOT - A Raspberry Pi IOT project (Blog Posting on SwitchDoc Labs)

Features

• Digital light sensor
• Wide spectrum detection range
• Programmable configuration
• 3.3/5V Supply
• Detect sunlight directly
• Grove compatible
• I2C Interface(7-bit)

Specifications

• Operating Voltage: 3.0-5.5V
• Working current: 3.5mA
• Wave length: 280-950nm
• Operating Temperature: -45C to +85C

Sunlight Sensor Board

• Grove Connector - a 4pin interface, contain VCC, GND, SDA and SCL
• LED - LED Driver pin
• INT - a programmable interrupt output
• SI1145 - IC

Spectrum

This content is from Wikipedia - Spectrum.

A spectrum (plural spectra or spectrums[1]) is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word was first used scientifically within the field of optics to describe the rainbow of colors in visible light when separated using a prism. As scientific understanding of light advanced, it came to apply to the entire electromagnetic spectrum.

Lumen

The lumen (symbol: lm) is the SI derived unit of luminous flux, a measure of the total "amount" of visible light emitted by a source. Luminous flux differs from power (radiant flux) in that luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light, while radiant flux measurements indicate the total power of all electromagnetic waves emitted, independent of the eye's ability to perceive it. Lumens are related to lux in that one lux is one lumen per square meter.

For some examples:

• Dark night: 0.001—0.02
• Moonlight night: 0.02—0.3
• Cloudy day indoor: 5—50
• Cloudy day outdoor: 50—500
• Sunny day indoor: 100—1000
• Suitable for reading: 500—600
• home video camera: 1400

Ultraviolet index

The following is from Wikipedia - Ultraviolet index.

The ultraviolet index or UV Index is an international standard measurement of the strength of sunburn-producing ultraviolet (UV) radiation at a particular place and time. The scale was developed by Canadian scientists in 1992, then adopted and standardized by the UN's World Health Organization and World Meteorological Organization in 1994. It is primarily used in daily forecasts aimed at the general public, and is increasingly available as an hourly forecast as well.

The UV Index is designed as an open-ended linear scale, directly proportional to the intensity of UV radiation that causes sunburn on human skin. For example, if a light-skinned individual (without sunscreen or a suntan) begins to sunburn in 30 minutes at UV Index 6, then that individual should expect to sunburn in about 15 minutes at UV Index 12 – twice the UV, twice as fast.

The purpose of the UV Index is to help people effectively protect themselves from UV radiation, which has health benefits in moderation but in excess causes sunburn, skin aging, DNA damage, skin cancer, immunosuppression,[1] and eye damage such as cataracts (see the section Human health-related effects of ultraviolet radiation). Public health organizations recommend that people protect themselves (for example, by applying sunscreen to the skin and wearing a hat and sunglasses) if they spend substantial time outdoors when the UV Index is 3 or higher; see the table below for more-detailed recommendations.

When the day's predicted UV Index is within various numerical ranges, the recommendations for protection are as follows:

Cautionary notes

When interpreting the UV Index and recommendations, be aware that:

• The intensity of UV radiation reaching the surface of the earth depends on the angle of the sun in the sky. Each day, the sun achieves its highest angle (highest intensity, shortest shadows) at solar noon, which only approximately corresponds to 12:00 on clocks. This is because of the differences between solar time and local time in a given time zone. In general, UV risk is high when the sun is directly enough overhead that people's shadows are shorter than their height.
• Likewise, UV intensity can be higher or lower for surfaces at different angles to the horizontal. For example, if people are walking or standing outdoors, UV exposure to the eyes and vertical surfaces of skin, such as the face, can actually be more severe when the sun is lower, such as the end of a summer's day, or winter afternoons on a ski trail. This is partly a consequence of the fact that the measurement equipment upon which the index is based is a flat horizontal surface.
• UV intensity can nearly double with reflection from snow or other bright surfaces like water, sand, or concrete.
• The recommendations given are for average adults with lightly tan skin. Those with darker skin are more likely to withstand greater sun exposure, while extra precautions are needed for children, seniors, particularly fair-skinned adults, and those who have greater sun sensitivity for medical reasons or from UV exposure in previous days. (The skin's recovery from UV radiation generally takes two days or more to run its course.)
• Because of the way the UV Index is calculated, it technically expresses the risk of developing sunburn, which is caused mostly by UVB radiation. However, UVA radiation also causes damage (photoaging, melanoma). Under some conditions, including most tanning beds, the UVA level may be disproportionately higher than described by the UV Index. The use of broad-spectrum (UVA/UVB) sunscreen can help address this concern.