View source for Light Sensing System Based on the Photoelectric Effect

= Editing Light Sensing System Based on the Photoelectric Effect =
== Team Member ==
Xu Ruizhe, Li Zerui, Ma Shunyu, Wei Heyi

== Overview ==
This project is designed to demonstrate the photoelectric effect by developing a smart light sensing system. The system detects ambient light intensity using a photoresistor (LDR) or a photodiode and processes the data using an Arduino or Raspberry Pi. When the light intensity crosses a predefined threshold, the system triggers a response, such as turning on an LED, activating a buzzer, or adjusting a curtain. This experiment integrates concepts from electromagnetism and the photoelectric effect into a practical and easy-to-implement application.

== Objective ==
The main objective of this experiment is to showcase how a light sensor converts optical signals into electrical signals and how these signals can be used to automate responses. By setting a threshold for light intensity, the system demonstrates real-world applications such as automatic lighting control, security alerts, and smart home automation. Additionally, this project provides hands-on experience with microcontrollers, sensor integration, and real-time data processing.

== Overview == 
Photoresistors are typically made from semiconductor materials such as cadmium sulfide (CdS), lead sulfide (PbS), or cadmium selenide (CdSe). These materials exhibit a change in conductivity when exposed to light.

In darkness, the semiconductor is in a nearly insulating state, with a small number of charge carriers (electrons and holes), resulting in high resistance.

Under illumination, if the energy of incident photons exceeds the band gap of the semiconductor, electrons in the valence band are excited into the conduction band, generating electron-hole pairs. This increases the concentration of free carriers, enhancing conductivity and reducing resistance.

== Principle of Humidity Sensor ==
The humidity sensor we use is from Seeed. It's a capacitor-based humidity sensor. 


== Equipment ==
*Light sensors
*Arduino
*Output devices (LED, OLED, buzzer)
*5V power supply