Design module to emulate PT2248 infrared signal decoding IC

Table of Content

• Overview
• IC PT2248
• Functional block diagram
• Broadcast principle
• Revenue principles
• NEC PROTOCOL
• Design control circuit on ALTIUM
• Design receiver circuit on Altium
• Result

Overview

Infrared light:

• Cannot be seen with the naked eye
• Frequency: 430 THz – 300 GHz
• Wavelength: 700 nm – 1 mm
• Very safe for the human body → long wavelength measurement
• Easily susceptible to interference: every object with a temperature greater than 0 degrees K emits infrared light

IC PT2248

IC PT2248 is an infrared transmitter using CMOS technology, the power supply voltage range is 2.2V~5V. Because it uses CMOS technology to manufacture, the power consumption is extremely low. It can hold down multiple keys at the same time (up to 6 keys), with very few external components.

Functional block diagram

Broadcast principle

Function block and coding block:

• Converts the control signal into the corresponding binary number in the form of a digital signal command code

Modulation block:

• Pair the command code into the carrier with frequency from 38KHz - 100KHz
• Helps increase transmission distance

Transmitter block:

• It is an infrared LED

Revenue principles

Receiver block:

• The infrared rays from the emitter are received by the photodiode

Amplifier and detector block:

• Amplify the received signal and then pass it through the parallel separation circuit to eliminate the carrier waves and extract the necessary data, which is the command code

Decoding block:

• Convert command code from binary number to corresponding decimal number

NEC PROTOCOL

A protocol that uses pulse distance coding The two logic levels 0 and 1 in the NEC protocol are defined as: Logic level 1: is a HIGH pulse with a period of 562.5𝜇𝑠 and a LOW level with a period of 1687𝜇𝑠 Logic level 0: is a HIGH pulse with a period of 562.5𝜇𝑠 and a LOW level with a period of 562.5𝜇𝑠

Design control circuit on ALTIUM

Design receiver circuit on Altium

Result