红外遥控基本知识

1、红外遥控基本知识By Robert Han1红外线介绍红外线的波长范围为760nm1500nm，我们所使用的遥控器发射的红外波长是940nm红外线遥控装置特点 体积小、功耗低、功能强、成本低等 2红外遥控系统红外遥控系统一般分发射和接收两个部分3红外线发射规范目前红外线的规范有NEC code, RC5, RC6, Toshiba code, Sharp code, Matsushita code, RCA code, RCMM code, Sony 20bit code, JVC code. and so on。NEC Code最常用，目前VIZIO使用是NEC Code4NEC Code

2、Format8 bit custom and 8 bit command lengthcustom and command are transmitted twicePulse distance modulationCarrier frequency of 38kHzLSB is transmitted firstly5NEC Code FormatLeader code: AGC burst(9ms)+Space(4.5ms)Custom code: data(8bit)+inverted data(8bit)Data code: data(8bit)+inverted data(8bit)

3、The length of one frame is 108ms6NEC Code FormatBit data formatLogical “0”:a high level of the duration T followed by a low level of duration 1T Logical “1”:a high level of the duration T followed by a low level of duration 3T Ps: T=0.56ms7NEC Code FormatCarrier formatfo=37.9kfz，占空比1/3可以减少干扰并提高发射效率8

4、NEC Code FormatFor Example “Menu” key transmit code: 00100 11000Custom code:00000100 0 x04Data code:01000011 0 x439NEC Code FormatRepeat CodeOne frame is 108msOne frame only contains 9.56ms carrier wave, which save power supply but be interrupted easily.10The Transmitter Consume as little power as p

5、ossible The current through the LED need to be as high as possible, in order to get an acceptable control distance, need refer to LED parameters, battery lifetime and maximum control distance.11The Transmitter12The ReceiverThe receiver includes photodiode and receiver IC, for example FM-6038LM-5AN13

6、The ReceiverAGC circuit get a constant pulse level regardless of the distance to remote controllerThe Band Pass Filter is tuned to the modulation frequencyWaveform detector is to detect the presence of the modulation frequency. If this modulation frequency is present the output will be low.Waveform rectifier14The ReceiverTburst时间愈长，其抗干扰能力愈好，NEC C