Uses ambient light to control the base of an internal NPN transistor.
Description:
An ambient light sensor, or phototransistor, senses changes in light intensity. The flow of electrical current between the emitter and collector varies based on the amount of light received.
How It Works:
This device is an NPN transistor where the base connection is replaced by an optical source. The base current from the photons is amplified by the transistor's gain.
Connect It:
This device has two wire leads. The Collector is connected to power, and the Emitter is connected to a voltage meter or analog input on a microcontroller, as well as to ground through a large resistor.
How It Is Used:
Select the device during simulation to show a slider representing light level. Slide the target to change the simulated light level.
Get Started:
Drag the starter circuit below into your design for a working example of how to use this part.
More About Phototransistor:
To add a Phototransistor in Tinkercad, search for "Phototransistor" in the component library, drag it onto your breadboard, and connect its terminals with wires to other components in your circuit. You can then click on the Phototransistor to set its name for easy identification.
Phototransistors are light-sensitive semiconductor devices that combine the functions of a photodiode and a transistor. They generate a current when exposed to light, and the current is amplified by the transistor’s gain, making them more sensitive than photodiodes. The main types of phototransistors are bipolar junction phototransistors (BJT) and field-effect phototransistors (FET), with BJTs being more common. Phototransistors can be NPN or PNP depending on their configuration, with NPN being the most widely used. Their key specifications include the wavelength range, typically from 350 nm to 1100 nm, depending on the material, with silicon-based phototransistors usually responding to light in the visible spectrum (400 nm to 700 nm). The photocurrent generated by the device is proportional to the light intensity, and the current gain (hFE) can range from 50 to over 1000, depending on the model. The dark current (current with no light) is typically very low, in the nanoampere (nA) range, and the saturation voltage is often between 1V and 5V. Power ratings for phototransistors typically range from 100 mW to 200 mW, and the reverse voltage rating is usually between 20V and 100V, depending on the specific phototransistor. The response time (rise and fall times) can range from microseconds to milliseconds, depending on the design and material. Operating temperature ranges for phototransistors are generally between -40°C to +85°C, and the unit of measurement for these parameters includes amperes (A) for current, volts (V) for voltage, watts (W) for power, and degrees Celsius (°C) for temperature.
1. Electronics Tutorials
Website Title: Electronics Tutorials
Website Page URL: https://www.electronics-tutorials.ws/io/phototransistor.html
URL recommended for: A comprehensive tutorial explaining how phototransistors work, their types, and their applications in electronic circuits. Ideal for beginners who want to grasp the fundamentals of phototransistors.
2. All About Circuits
Website Title: All About Circuits
Website Page URL: https://www.allaboutcircuits.com/textbook/semiconductors/chpt-6/phototransistors/
URL recommended for: An in-depth guide on phototransistors, including their theory, applications, and comparison with photodiodes. Great for both beginners and intermediate learners.
3. Digi-Key Electronics - Phototransistors
Website Title: Digi-Key Electronics
Website Page URL: https://www.digikey.com/en/products/filter/phototransistors/748
URL recommended for: A wide selection of phototransistors with detailed datasheets, specifications, and available product options. Great for those who want to explore component choices and technical details.
4. RS Components - Phototransistors
Website Title: RS Components
Website Page URL: https://uk.rs-online.com/web/c/semiconductors/optoelectronics/phototransistors/
URL recommended for: An extensive catalog of phototransistors with product datasheets and specifications, perfect for understanding different types and selecting the right phototransistor for specific projects.
5. Adafruit - Light Sensors
Website Title: Adafruit
Website Page URL: https://learn.adafruit.com/phototransistor
URL recommended for: A beginner-friendly guide to phototransistors, with clear explanations and examples of how they work in electronics projects. Great for hands-on learners.
6. SparkFun Electronics - Phototransistor Guide
Website Title: SparkFun Electronics
Website Page URL: https://learn.sparkfun.com/tutorials/phototransistors
URL recommended for: An easy-to-understand guide to phototransistors, with tutorials and projects that integrate phototransistors into real-world applications. Ideal for learning through practical examples.
7. OptoSigma - Phototransistors
Website Title: OptoSigma
Website Page URL: https://www.optosigma.com/us/en/products/optoelectronics/phototransistors
URL recommended for: A specialized resource with detailed descriptions and specifications of different phototransistors used in optoelectronics. Perfect for those seeking high-precision components.
8. Learn Spark - Phototransistors and Light Sensors
Website Title: Learn Spark
Website Page URL: https://learn.sparkfun.com/tutorials/light-sensors
URL recommended for: A helpful guide for beginners looking to integrate phototransistors and light sensors into projects, with step-by-step instructions and examples.
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…till next post, bye-bye & take care.
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