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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 with your own .
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.
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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.
trum123 wrote : (21-Jul-2005 9:36 AM)
Do you have an idea to use IR remote control
reversing 12V DC motor?
thecop wrote : (21-Jul-2005 03:55 PM)
Hay
I looking for this idea too.
I need to control the motor for roll up and down
my projector screen.
Any one have idea ?
thank
Here is an example application for reverse direction of dc motor
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