IR light is like visible light, but invisible to our eyes, so it is suitable for wireless communication applications. The IR band (infrared) in the electromagnetic spectrum ranges from 300 GHz to 430 THz and a wavelength range from around 700 nm to 1 mm. Besides the IR LED, some other sources such as the sun, lightbulbs, human and animal bodies, etc. also emit infrared energy. IR communication is used for short and medium distances.
Table of contents
Principle of Working
IR LEDs transmit digital data (logic 1 and 0) in the form of infrared light. Logical 1 is output by keeping the IR LED on and logic 0 by keeping it off. This sequence of on-off data is collected by an IR photodiode at the end of the receiver.
Types of IR communication
1) Point-to-point communication: With point-to-point communication, a line of sight between the sending and receiving devices is required.
2) Fuzzy communication: With diffuse communication, it is not necessary to keep the transmitter and receiver in a straight line of sight. This can be done by reflecting or reflecting the transmitted signal off surfaces such as walls, ceilings, etc.
IR Communication using Modulation
In modulating IR communication, the IR light is modulated at carrier frequencies in order to obtain a better available distance. It also offers better immunity to surrounding IR interference. In general, TSOP series receivers are used to receive modulated IR light.
IR LEDs with wavelengths from 940 nm to 950 nm are usually used for infrared transmission. When we transmit the data to the infrared receiver, the infrared receiver also receives infrared rays from the environment at the same time. These infrared rays from the environment can be distorted. The transferred data. In order to avoid such environmental disturbances, the IR signal can be modulated with carrier frequencies. Commonly used carrier frequencies are 30 kHz, 36 kHz, 38 kHz, 56 kHz etc. in IR communication, NEC code, Toshiba Micom Format, Sharp Code, RC5 Code protocols, RC6 code, R-2000 Code, Sony format (SIRCS) etc. used, a simple RS232 serial communication protocol can also be used for IR communication. This protocol uses one start bit, 8-bit data, one parity bit (optional). ) and a stop bit format.
On the receiver side, the infrared receiver receives data with a carrier frequency of 38 kHz. The epoxy package is designed for the infrared filter. This module is designed to avoid unexpected output pulses due to noise or spurious signals. They have used that support the reception of various transmitted codes. A continuous data rate of up to 2400 bps is possible in TSOP1738. This demodulated output signal is received by the microcontroller.