Is everything visible around you? Are you only grabbing benefits from the visible things only? No. Many invisible phenomena exist on our Earth, with which we are accomplishing our desires! Such a phenomenon is the infrared ray. The wavelength of the ray typically ranges from 700 nm to 1 mm. Infrared, or IR sensors are mostly used sensors that we use in TV remotes to detect obstacles in robots because of their simplicity and versatile working capability.
What is an Infrared (IR) Sensor?
An electronic device that emits and detects infrared radiation to sense objects in its surrounding environment is an infrared (IR) sensor, which powers industrial automation systems. An electronic device that emits and detects infrared radiation to sense objects in its surrounding environment is an infrared (IR) sensor, which powers industrial automation systems. These electronic gadgets receive or produce infrared radiation, a type of electromagnetic energy imperceptible to the human eye, allowing machines to see and engage with their surroundings in manners that emulate biological senses.
Working Principle: How it works?
For a deep dive into the infrared sensors, their mechanism of working should be studied. Here, two key components are involved in the operation of an infrared sensor: an IR emitter and an IR detector.
The Infrared Emitter: It’s the origin of invisible light. An Infrared Light Emitting Diode (IR LED) is the most widely used IR emitter. An IR LED uses infrared wavelengths to transform electrical energy into light, just like a conventional LED. These LEDs are made especially to emit infrared light, which is subsequently focused on a target or other area of interest. In more specializeds where highly focused beams are needed, infrared lasers are also employed.
IR Detector: It senses invisible things. The IR photodiode is the main part in charge of sensing infrared radiation. A semiconductor device known as an infrared photodiode changes its electrical characteristics, particularly its output voltage and resistance, when it is subjected to infrared light. The intensity of the incident infrared light directly correlates with this shift. Phototransistors are additional detectors that provide greater amplification and sensitivity.
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| Basic principle of an IR sensor |
When an infrared transmitter and receiver are used together, the wavelengths of the transmitter and receiver must match. In this case, an IR LED serves as the transmitter and an IR photodiode as the receiver. The infrared light produced by an infrared LED causes the infrared photodiode to react. The amount of infrared light produced is proportional to the photo-diode's resistance and the output voltage variation. This is the basic idea behind how an infrared sensor operates. When the emission from the infrared transmitter reaches the item, some of it will reflect back to the infrared receiver. The IR receiver can determine the sensor output based on the response's intensity.
Steps are at a glance:
- The IR LED emits infrared light.
- If there’s a reflective object in front, IR rays reflect back.
- The photodiode senses the reflected IR light.
- The amount of light received affects the current through the photodiode.
- This current is converted into a voltage and sent to an Op-Amp comparator.
- If the voltage is above a set threshold, the sensor outputs a HIGH signal (usually 5V), indicating the presence of an object.
Explanation of IR Sensor's Circuit Diagram:
The IR sensor serves its purpose by developing a circuit that includes major components: infrared LED, photodiode, variable resistor/potentiometer, and capacitors. Infrared light is continuously emitted by the IR LED. This light is reflected back at the photodiode by an object positioned in front of it.
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| Circuit Diagram of IR Sensor (Source: circuitdigest.com) |
The IR sensor circuit diagram shows the connections. The photo diode is placed in reverse bias, and the inverting end of LM358 (PIN 2) is linked to the variable resistor to modify the sensor's sensitivity. The non-inverting end (PIN 3) is linked to the junction of a photodiode and resistor. When we turn on the circuit, there is no IR radiation towards the photodiode, and the comparator's output is LOW. When we place a non-black object in front of an IR pair, the IR emitted by the IR LED is reflected and absorbed by the photodiode.
When reflected IR falls on the photodiode, the voltage across the photodiode decreases while the voltage across series resistor R2 increases. When the voltage at resistor R2 (attached to the non-inverting end of the comparator) exceeds the voltage at the inverting end, the output becomes HIGH and the LED turns on. The voltage at the inverting end, commonly known as the threshold voltage, can be adjusted by moving the variable resistor knob. The higher the voltage at the inverting end (-), the less sensitive the sensor; the lower the value at the inverting end, the more sensitive the sensor.
Types of IR sensors:
Active Infrared Sensors: These sensors combine an infrared emitter (transmitter) and a receiver (receiver) into one unit or in independent parts that face one another. Emitting infrared light and then detecting the reflected or interrupted radiation is how they work.
Reflective infrared sensors: These sensors have the emitter and detector positioned next to each other. The photodiode detects the infrared light that the LED emits after it bounces off an object. These are frequently utilized in line following, robot obstacle avoidance, and proximity sensing.
Transmissive infrared sensors, also known as photo-interrupters, have a gap between the emitter and detector, which are oriented facing one another. The detector's output changes when an object disrupts the infrared beam as it travels through this gap. Limit switches, rotating encoders, and object counting are a few examples of applications.
Passive infrared sensors: This kind of sensor doesn't release any infrared radiation, in contrast to active sensors. Rather, they are limited to detecting infrared light that is naturally generated by objects inside their field of vision. Based on variations in the infrared energy patterns in their surroundings, PIR sensors are mostly employed to identify motion or the presence of warm bodies (such as people or animals).
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IR Sensor Applications:
Advantages of using IR sensors:
Non-Contact Detection: Prevents contamination or wear and tear by enabling detection without physical contact.
Low Power Consumption: Because many infrared sensors use little energy, they can be used with devices that run on batteries.
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Limitations of IR sensors:
Read more: PIR Sensor Working details.
Frequently Asked Questions (FAQs)
1. What is an infrared (IR) sensor?
An infrared (IR) sensor is an electronic device that detects infrared radiation emitted or reflected by objects. It is commonly used for object detection, distance sensing, motion detection, and remote control applications.
2. What is the working principle of an IR sensor?
An IR sensor works by transmitting infrared light from an IR LED and detecting the reflected light using a photodiode or phototransistor. When an object is within the sensing range, the reflected infrared light is detected, causing the sensor to generate an output signal.
3. What are the main components of an IR sensor?
A typical IR sensor consists of:
- IR LED (Infrared Transmitter)
- Photodiode or Phototransistor (Receiver)
- Signal Processing Circuit
- Comparator or Amplifier
- Output Interface
4. What are the different types of IR sensors?
IR sensors are mainly classified into two types:
- Active IR Sensors: Use both an infrared transmitter and receiver to detect reflected infrared light.
- Passive IR (PIR) Sensors: Detect infrared radiation naturally emitted by humans and animals without transmitting infrared light.
5. What is the difference between an active IR sensor and a PIR sensor?
An active IR sensor emits infrared light and detects its reflection from nearby objects, making it suitable for obstacle detection and proximity sensing. A PIR sensor does not emit infrared light; instead, it detects changes in infrared radiation from warm objects, making it ideal for motion detection and security systems.
6. What is the typical sensing range of an IR sensor?
The sensing range depends on the sensor module and the object's surface. Most standard IR proximity sensors can detect objects within approximately 2 cm to 30 cm, while specialized IR sensors may offer longer detection distances.
7. What factors affect the performance of an IR sensor?
Several factors can influence IR sensor performance, including:
- Object color and surface reflectivity
- Ambient sunlight or strong infrared sources
- Sensor alignment
- Detection distance
- Dust, dirt, or moisture on the sensor
8. What are the common applications of IR sensors?
IR sensors are widely used in:
- Obstacle-avoidance robots
- Automatic doors
- Line-following robots
- TV remote controls
- Security systems
- Industrial automation
- Object counting systems
- Parking assistance systems
9. Can an IR sensor detect transparent objects?
Most standard IR proximity sensors have difficulty detecting transparent objects such as clear glass because infrared light passes through them with minimal reflection. Specialized sensors are required for reliable transparent object detection.
10. Can an IR sensor work in sunlight?
Yes, but direct sunlight can interfere with the infrared signals and reduce detection accuracy. Many modern IR sensors use modulated infrared signals and optical filters to minimize the effects of ambient light.
11. How is an IR sensor connected to an Arduino?
Most IR sensor modules have three pins:
- VCC – Connect to 5V or 3.3V
- GND – Connect to Ground
- OUT – Connect to any digital input pin of the Arduino
The Arduino reads the output pin to determine whether an object is detected.
12. What are the advantages of using an IR sensor?
Some key advantages include the following:
- Low cost
- Low power consumption
- Fast response time
- Simple interface with microcontrollers
- Compact size
- Reliable short-range object detection
13. What are the limitations of IR sensors?
The main limitations are the following:
- Limited sensing range
- Performance affected by sunlight
- Reduced accuracy on black or highly reflective surfaces
- Difficulty detecting transparent objects
- Not suitable for long-distance measurement
14. What is the difference between an IR sensor and an ultrasonic sensor?
An IR sensor uses infrared light to detect objects, while an ultrasonic sensor uses high-frequency sound waves. Ultrasonic sensors generally provide longer detection ranges and are less affected by object color, whereas IR sensors are faster, smaller, and more economical for short-range applications.
15. Why is an IR sensor widely used in robotics?
IR sensors are popular in robotics because they are inexpensive, easy to interface with microcontrollers like Arduino, consume very little power, and provide quick and reliable obstacle detection for navigation and automation tasks.
Conclusion... Modern electronics rely heavily on infrared sensors because of their affordability, ease of use, and adaptability. IR sensors provide a dependable solution for proximity and motion detection, whether you're building a basic robot that avoids obstacles or automating a security system. They do have certain drawbacks, especially with regard to range and susceptibility to outside interference, but these may be mostly addressed with appropriate circuit design and modulation methods.
Their wide range of uses in consumer electronics, industrial automation, robotics, and medical equipment show how essential infrared sensors are to the development of intelligent systems. Gaining insight into the inner workings of infrared sensors not only improves your understanding of electronics but also leads to a plethora of professional and do-it-yourself automation and control system opportunities.
Written by: Md. Mahabub Hasan
Md. Mahabub Hasan is an electrical engineer with experience in industrial automation, SCADA systems, and embedded systems development. He writes technical articles on electrical engineering, automation systems, microcontrollers, and industrial communication protocols. He is the founder of Electrical-Info.net, a website dedicated to providing practical knowledge on electrical and electronic engineering.
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