Circuit Lake

Remote controlled audio/video switching is not a new concept, but modern microcontrollers allow designers to incorporate functionality that was quite difficult in the past. Specifically, it is now possible using microcontrollers equipped with EEPROM and SRAM to capture IR signals and store their timing data for use as reference profiles that allow the device to respond to any compatible remote control transmitter the user may wish to utilize.

“The concept is fairly simple. A signal is detected, captured to SRAM, trimmed as needed, and finally stored to an EEPROM location that is associated with a particular button or function on the device. This is generally referred to as a “learning” device. Traditionally, most learning devices have been universal remote controllers,” said Thomas Couey, the project designer.

The hardware for this project was designed from scratch as a fully solid-state switching solution for stereo audio signals and an associated composite video signal. The microcontroller used is AVR ATmega88, the other chips are mostly Maxim components: MAX232, MAX1044, MAX454, and a DG409. A voltage regulator (LM2940) is also used. The MAX1044 is a switched-capacitor voltage converter used to generate a -5V bias required by the op-amps inside the MAX454 and DG409 ICs. The MAX454 switches 4 video sources to one output, while the DG409 does the same for stereo line level audio signals.