INFRARED TV REMOTE DECODER
This device converts the code of TV remote control into RS232 code. There are many infrared code systems in use, they vary in number of bits in a word and the number of words. The encoder works well when used with a TV remotes that transmit 16 bits, i.e. JVC remote, when used with TV remotes that transmit more than 16 bits several keys will give the same output from the encoder. The output of the converter connects to the serial port. Included a Visual Basic code for reading the numeric value of the converted infrared.
The common waveform to most IR systems is the start of a low pulse of 9.6mS followed by a positive pulse of 4.5mS and then the bits. A bit pulse of 1.2mS represents binary 0 and pulse of 1.8 mS represents binary 1. This encoder measures the duration of the pulses and constructs 2 words of 8 bits and send them to the UART in the PIC16F628A.
You can read more about IR in here, and about serial interface in here
Software includes PIC code and VB6 code (10KB). You are free to use the circuit diagram and the software with no
The VB6 interface
See also Technical Tips
Pin 4 at the serial port is
turned to +12V by the software enabling RTS. It is regulated to
5V by 78L05. The 5V is the supply to the microcontroller.
Pin 3 is at -12V and pin 7 at +12V
constantly and they are used to drive RX input between -9V (input
HIGH) and +8v (input LOW) . These levels are sufficient to drive
the RS232 input.
Transistors BC237 and BC327 are level shift from 0 to 5V of the PIC output to about +/- 5V needed for the serial port.
PIC16F628A contains a UART for serial comm port. Pin 8 is the UART output, it transmits the 16 bit in RS232 format.
IR detector is a receivers for infrared remote control systems, PIN diode and preamplifier. It can be TSOP1138, TSOP1238, SFH 506-38 or equivalent.