32 Channel IR Remote Controller by SL490

This is a 32 channel infrared remote controller circuit fundamentally includes key pad, decoder, transducer stage, an output and a battery. Circuit is like a pocket calculator in size. Commands are formed by using 8 x 4 matrix with 32 switches.

Be aware that only one switch functions at one time and during one command is been generating, input circuitry is irresponsive to the other commands .

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

Pulse and gap lengths are calibrated by using P1 potentiometer.

Length ratio between logic 0 and logic 1 is (1.5 / 1). Pulse length between two 54ms code word is about 3ms.

Transmitter transmits infrared light only when IC1′s 3 numbered pin is high.

SL490 includes an auto stand-by circuitry. When the buttons are not used for a while, IC will switch to stand-by mode and stand-by current will be 6uA.

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