1、红外遥控基本知识,By Robert Han,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,红外遥控系统,红外遥控系统一般分发射和接收两个部分,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 Code,NEC C
2、ode Format,8 bit custom and 8 bit command length custom and command are transmitted twice Pulse distance modulation Carrier frequency of 38kHz LSB is transmitted firstly,NEC Code Format,Leader code: AGC burst(9ms)+Space(4.5ms) Custom code: data(8bit)+inverted data(8bit) Data code: data(8bit)+inverte
3、d data(8bit) The length of one frame is 108ms,NEC Code Format,Bit data format Logical “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=0.56ms,NEC Code Format,Carrier format fo=37.9kfz，占空比
4、1/3 可以减少干扰并提高发射效率,NEC Code Format,For Example“Menu” key transmit code:00100000 11011111 11000010 00111101 Custom code:00000100 0x04 Data code:01000011 0x43,NEC Code Format,Repeat Code One frame is 108ms One frame only contains 9.56ms carrier wave, which save power supply but be interrupted easily.,T
5、he Transmitter,Consume as little power as possible 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.,The Transmitter,The Receiver,The receiver includes photodiode an
6、d receiver IC, for example FM-6038LM-5AN,The Receiver,AGC circuit get a constant pulse level regardless of the distance to remote controller The Band Pass Filter is tuned to the modulation frequency Waveform detector is to detect the presence of the modulation frequency. If this modulation frequency is present the output will be low. Waveform rectifier,The Receiver,Tburst时间愈长，其抗干扰能力愈好，NEC CODE: Tburst=560us、 Tgap=560us、 Tpause=30.94 48.94ms,TV红外接收距离,角度=30时：10m 角度=45时：7m 角度=60时：3m 角度定义如图,
