* Question

What is the detection method for the sunshine sensor?

* Answer

Sunshine sensors—also called solar radiation sensors, pyranometers, or sun presence sensors—are used to detect sunlight intensity, solar irradiance, or direct sun position. Depending on the application (automotive, solar energy, meteorology, building automation), the detection method differs. Overall, sunshine sensors fall into three main detection categories.

1. Photoelectric Detection (Photodiodes / Photocells) – Most Common Method

Most sunshine sensors use photodiodes or photovoltaic cells to convert light into electrical signals.
This is the standard method used in automotive HVAC sunlight sensors, building automation, and compact weather stations.

How it works

• A photodiode generates a small current proportional to incident solar radiation.
• The sensor typically includes two channels:
  • Visible light channel (VIS)
  • Infrared channel (IR)
• By comparing VIS and IR outputs, the system determines:
  • Sunlight presence
  • Sun angle (left/right illumination in cars)
  • Intensity (lux / W/m²)

Advantages

• Simple and low cost
• Fast response time
• Easy to integrate into embedded systems

2. Thermal Detection (Thermopile Pyranometers) – High-Accuracy Meteorological Method

Professional meteorological sunshine sensors use a thermopile-based pyranometer.

How it works

• A blackened thermopile absorbs solar radiation.
• The absorbed energy heats the junctions, creating a voltage proportional to total solar irradiance.
• A precision dome filters out unwanted wavelengths.

Advantages

• Very high accuracy
• Measures broadband solar irradiance (global solar radiation)
• Suitable for solar farm monitoring and meteorological stations

Variants

• Pyrheliometers– measure direct beam solar radiation
• Pyranometers– measure global (diffuse + direct) irradiance

3. Position Detection (Optical Tracking + Shadowband / Fin Sensors)

Some sunshine sensors detect whether the sun is above the horizon or determine sun position using mechanical or optical structures.

Common methods

• Shadowband sensors– detect direct sun by blocking diffuse light
• Sun-tracking sensors– use quadrant photodiodes to find sun angle
• Fenestrated “sun presence” sensors– detect when sunlight passes through a slit

Applications

• Solar trackers
• High-precision daylighting systems
• Radiometric calibration systems

Summary Table