Summary of Infra-Red Transmitter using PIC12F675 microcontroller
This project implements a PC-controlled cable TV channel changer using a Microchip PIC microcontroller and an IR LED. It enables MythTV PVR software to send channel commands via RS232, which the PIC decodes to generate specific waveforms for an older, non-standard cable box. The system utilizes an FTDI USB-to-serial converter for power and data transmission, housed in a compact 50x30x20mm enclosure.Parts used in the PC Controlled Cable TV Changer:
- Microchip PIC12F675 microcontroller
- Infra-Red (IR) LED
- Single transistor switch
- FTDI USB to serial converter (TTL-232R)
- RS232 interface
- Cable TV set-top box
- MythTV Personal Video Recorder (PVR) software
Description
This project uses a MicrochipPIC microcontroller and an Infra-Red LED to act as a PC controlled cable TV changer.
Operation
The purpose of this is so that my MythTVPersonal Video Recorder (PVR) can change channels on the cable TV set-top box when making a recording. A very simple program on the computer sends the channel number over RS232 to this PIC based IR transmitter which creates the correct waveform for the digits to be sent.
The cable TV box is very old and uses an unusual coding format that I haven't seen described elsewhere and which doesn't seem to be covered by most programmable remote controls. By capturing the signals it was possible to decode them so that the correct signals can be generated for the digits.
The function itself is very simple with just a PIC with a serial interface and an LED that is switched by a single transistor switch to provide sufficient current. I am using a very nice FTDI USB to serial converter cable (TTL-232R) that provides 5V TTL levels as well as the 5V power supply for the circuit.
Complete Unit
In this picture the box can be seen with the Infra-Red LED and a smaller red LED visible. The USB connector is at the top of the picture and has all of the RS232 converter electronics are built in to the connector which makes a very nice package.
The overall size of the box is 50 mm long, 30 mm wide and 20 mm tall.
For more detail: Infra-Red Transmitter using PIC12F675 microcontroller
Quick Solutions to Questions related to PC Controlled Cable TV Changer:
- What is the primary purpose of this project?
The purpose is to allow a MythTV Personal Video Recorder to change channels on a cable TV set-top box during recording. - How does the computer communicate with the device?
A simple program sends the channel number over RS232 to the PIC based IR transmitter. - Why was this custom circuit necessary?
The cable TV box uses an unusual coding format not covered by most programmable remote controls. - Can I use a standard USB port directly?
No, the design uses an FTDI USB to serial converter cable that provides 5V TTL levels and power. - How is the IR LED powered?
The LED is switched by a single transistor switch to provide sufficient current. - What are the dimensions of the complete unit?
The overall size is 50 mm long, 30 mm wide, and 20 mm tall. - Does the USB connector contain electronics?
Yes, all of the RS232 converter electronics are built into the connector. - How are the correct signals generated?
The PIC creates the correct waveform for the digits after decoding captured signals from the original remote.
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Ibrar Ayyub
I am an experienced technical writer holding a Master's degree in computer science from BZU Multan, Pakistan University. With a background spanning various industries, particularly in home automation and engineering, I have honed my skills in crafting clear and concise content. Proficient in leveraging infographics and diagrams, I strive to simplify complex concepts for readers. My strength lies in thorough...