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3 channel IR remote control 5-July-2005 www.sixca.com This project is a 3-channel IR remote control with 3 output relay and easy to build. Feature : CPU PIC12F629 at 4MHz crystal for Tx/Rx 3 channel output relay The Tx use sleep mode for saving battery power Use Phillips RC5 protocal distance more than 7 m. Easy circuit to build and assembly small components Basic RC5 protocal The RC5 is probably the most used by hobbyists, probably because the wide availability of cheap remote controls and easy to understand. Feature : 2 start bit always "1" 1 toggle bit but this project not use and always "0" 5 bit address and 6 bit command length Bi-phase coding (aka Manchester coding) Carrier frequency of 36kHz 25-50% duty cycle Bit time period about 1.67 ms Developt by Philips The protocol uses bi-phase modulation (or Manchester code) of a 36kHz IR carrier frequency. All bits are of equal length of about 1.67 ms as follows figure. Figure 1. RC5 Modulation Figure 2. RC5 Frame format Figure 3. Bi-Phase coding In figure 2,the first two pulses are the start pulses, and are both logical "1". (St1 and St2) The 3d bit is a toggle bit. This bit is inverted every time a key is released and pressed again. But this project not use this bit and always "0" (Ctrl) The next 5 bits represent the IR device address, which is sent with MSB first. (S0-S4) The next 6 bits is command and sent with MSB first too.(C0-C5) Note that a RC5 frame consists of a total of 14 bits so the total time is about 23 mS RC5 detecting When the detect subroutine is called, it first waits for a start bit. The length of the low part of the first start bit is measured. If the low pulse of first start bit is longer than 1.020 ms or less then 800 uS the routine returns indicating error or no command received. Figure 4. Synchronizing and Sampling of the Data The measurement of the start bit is used to calculate two reference times, ref1 and ref2, which are used when sampling the data line. The program uses the edge in the middle of every bit to synchronize the timing. 3/4 bit length after this edge, the line is sampled. This is in the middle of the first half of the next bit (see Figure 4).The state for each bit is stored and the routine waits for the middle edge. Tx schematic The TX use 8 pin PIC devices, here is PIC12F629 run at 4 MHz crystal. Actualy, this device has 4MHz RC internal oscillator but not suitible for use with the project that need cirtical time as remote control.The 36KHz carrier and information bit generated by IC1.For saving power when use with battery powered we need to use this device in sleep mode when any keys not pressed and draw current <1 mA at 4MHz, 5.5V . Example how to wake-up from sleep mode when key pressed.
    main :  SLEEP
              BTFSS      CH1
              GOTO       Do_CH1
              BTFSS      CH2
              GOTO       Do_CH2
              BTFSS      CH3
              GOTO       Do_CH3
              GOTO       main
Rx schematic The IR was recieved from Tx will demodulated by IC2 that is IR receiver Modules for Remote Control Systems.In this project I use TSOP4836 from Vishay Semiconductors that is one of TSOP48XX series. After IR demodulated it was decoded the protocal by IC1 then turn on/off appropiate channel.The out out of IC1 is toggle every time when Tx send the same command to Rx.You may be change the output drive circuit for suitible with your load.The pin 3 of IC1 must pull-up to vcc with R10K becuase it is not has weak-up internal pull-up. Here is an example application for reverse direction of dc motor Note : don't for got to connect diode cross relay Download source other PIC projects ICD2 clone Programmer and Debugger for Microchip devices ATMEL ISP In-System programmer for ATMEL AT89S series AVR ISP In-System programmer for ATMEL AVR series
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