TV remote control Circuit diagram using SL490
This is a 32 channel infrared remote controller circuit fundamentally includes key pad, decoder, transducer stage, an output and a battery.
Every key pad button generates 5 bit binary code and IC1 sends this code to the IR leds through D1 and D2 diodes. Code is shaped from 6 pulses with 5 gaps. Pulse position modulation – PPM technique is used for transferring data. Data information occurs at gaps. For logic 0, long gap, for logic 1 short gap is generated. SL490 includes an auto stand-by circuitry. When the buttons are not used for a while, IC will swich to stand-by mode and stand by current will be 6uA.
Pulse and gap lengths are calibrated by using potentiometer.