IR TRANSCEIVER

General Description:

An IR sensor can measure the heat of an object as well as detect the motion. There are two types of IR sensors. They are:

• Active Infrared Sensor: Active infrared sensors consist of two elements: an infrared source and an infrared detector. Infrared sources include the LED or infrared laser diode. Infrared detectors include photodiodes or phototransistors. The energy emitted by the infrared source is reflected by an object and falls on the infrared detector.
• Passive Infrared Sensors: They are of two types: quantum and thermal. Thermal infrared sensors use infrared energy as the source of heat. Thermocouples, pyroelectric detectors, and bolometers are the common types of thermal infrared detectors. Quantum-type infrared sensors offer higher detection performance. It is faster than thermal-type infrared detectors. The photo sensitivity of quantum-type detectors is wavelength-dependent.

Working Principle:

There are different types of infrared transmitters depending on their wavelengths, output power and response time. An IR sensor consists of an IR LED and an IR Photodiode, together they are called as PhotoCoupler or OptoCoupler.

IR Transmitter or IR LED: Infrared Transmitter is a light-emitting diode (LED) which emits infrared radiations called as IR LED's. Even though an IR LED looks like a normal LED, the radiation emitted by it is invisible to the human eye.

IR Receiver or Photodiode: Infrared receivers or infrared sensors detect the radiation from an IR transmitter. IR receivers come in the form of photodiodes and phototransistors. Infrared Photodiodes are different from normal photodiodes as they detect only infrared radiation.

Different types of IR receivers exist based on the wavelength, voltage, package, etc. When used in an infrared transmitter-receiver combination, the wavelength of the receiver should match that of the transmitter.

The emitter is an IR LED and the detector is an IR photodiode. The IR photodiode is sensitive to the IR light emitted by an IR LED. The photo-diode resistance and output voltage change in proportion to the IR light received. This is the underlying working principle of the IR sensor.

When the IR transmitter emits radiation, it reaches the object and some of the radiation reflects to the IR receiver. Based on the intensity of the reception by the IR receiver, the output of the sensor is defined.

Specifications:

1. The main chip of the sensor is LM393.
2. It operates at an operating voltage of 3.6 to 5 volts.
3. The average current consumption of the sensor is 0.06 mA.
4. The detection angle of the sensor is 35 degrees.
5. The distance measuring range of the sensor is 2 to 30 cm.

Applications:

1. Night Vision Devices
2. Radiation Thermometers
3. Infrared Tracking
4. IR Imaging Devices