Project Name: Mini "Mute" Remote Control (Inspired by Adafruit's "TV-b-gone kit")
Author/Designer: Y H
Project Description: A small remote control with one button. When the button is pressed, it mutes the television. Only Sony TVs are supported, but it can be programmable to support other TVs, provided the respective signal profiles are observed.
The remote control can be also modified to send other codes such as "Turn Off" and others.
Photo/Picture/Figure/Diagram/Flowchart: The remote control data is sent in a bit-width system and modulated by a 36~40kHz carrier wave with a 25% duty cycle. An '1' means with a 600microsec 'low' and a 600microsec 'high', while '0' means 600microsec 'low' and 1200microsec 'high'.
The pulsing of the data can be done by simple delay codes while the carrier waves can be generated by just using the PWM module present in the microcontroller.
The mechanism is simple:
1.) PWM is set up. A 2400milisec pulse is asserted and sent to the target as a 'start'.
2.) The RC then send another 6 bits of information. These 6-bits are for commanding the target to do something.
3.) The RC then send another 4 bits of address information. These 4-bits are address of the target. All of these are transferred from the Lowest Significant Bit.
4.) The command is sent 3 times (1->3). Afterwards, microcontroller goes to sleep to conserve battery.
Source: Sony IR (infrared) remote control codes
Sony Remote Control Code Lists
Use IR_send(<remote control code>) and do it three times in the loop so that the TV can receive it completely.
The 'low' signal shuts (disables) the PWM pin so that no modulating waves are present, while the 'high' signal enables the PWM pin so that the waves comes into the target.
Compiler: MikroC 5.6.0 (code within 2K limits)
Source code: Attached.
Schematics & PCB Docs:
Hardware: PIC16F1503, 2N3904 transistor, IR LED, 270ohm resistor, 10ohm resistor, 10k ohm resistor, push button, 2AA battery holder.
References: Microchip AN1064: IR Remote Control Transmitter. Schematic is based on the application note.