The LED is connected to one of the Raspberry Pi’s GPIO pin. Each line is connected to a pull-up resistor of 10k Ohms. I2C Signal Line Connectionsīoth the SDA and SCL pins of the Raspberry Pi and PCF8591 are connected to each other. This will allow the PCF8591’s AD Converter to read the analog value of the photoresistor. The AIN0 pin of the PCF8591 is connected in parallel to the photoresistor. To get a better picture of how our circuit works, here is the schematic diagram of our Photoresistor Raspberry Pi Interfacing Tutorial: Photoresistor ConnectionsĪ pull-up resistor of 10k Ohms is connected to photoresistor to set the undefined state to 3.3 V. To sum it up, the resistance variation on the photoresistor causes the LED’s brightness to change. The digital quantity read from the DA Converter will be used to vary the PWM signal to the LED. It will then send a digital quantity representation of the analog signal to the Raspberry Pi. The PCF8591 is responsible for reading the analog signal from the Photoresistor. To setup this circuit, we will need the following parts: The less light the photoresistor detects, the higher the intensity of the LED will be. In this tutorial, we will be using the photoresistor, as an input, to control the brightness of the LED. Setting Up Our Photoresistor Raspberry Pi Tutorial Circuit (Left) Resistance w/o Light (Right) Resistance w/ Lightīecause of the photoresistor’s ability to change resistance due to light, it is widely used in light detecting applications such as alarm devices, outdoor lights, solar trackers, etc. Testing the Photoresistor with a Multitester. The higher the intensity of light falling on the photoresistor, the lesser resistance the photoresistor will be. Its resistance value significantly depend on the amount of light that hits the photoconductive material of the photoresistor. What’s a Photoresistor?Ī photoresistor is a resistor that is sensitive to light. You can check out our Potentiometer Raspberry Pi Tutorial to learn more about interfacing an AD/DA Converter with a Raspberry Pi. Thus, knowing how to interface the Raspberry Pi with an AD/DA Converter is necessary. The Raspberry Pi cannot read analog signals directly so an AD Converter is necessary to read the photoresistor’s analog signal. Also, we will learn how to use an Analog-to-Digital Converter to read the analog signal from the photoresistor using a Raspberry Pi. * Connect one end of the photocell to 5V, the other end to Analog 0.In this Photoresistor Raspberry Pi Interfacing Tutorial, we will learn how to connect a photoresistor to a Raspberry pi. * Program: Photocell simple testing sketch.

Photoresistor circuit arduino