This is a precision 38 kHz Infrared transmitter using MOS integrated circuit uPD 6121.It uses the NEC transmission format ideally suited for remote operation in TV, VCD Player etc. The NEC transmission format includes leader codes, custom codes (16 bits), and data codes (16 bits).The frequency of oscillation is determined by the Crystal. The IR LEDs connected to the output emits IR pulses at 38kHz.The circuit is ideal for most IR Sensors since these are designed for 38 kHz pulsed IR rays.
The circuit uses IC uPD6121. It is a CMOS version designed for IR transmission. It operates between 2 and 3.3 volts DC and maximum current consumption is 1 uA. It is a 20 pin IC.
Data codes of IC uPD 6121.
32 Codes single inputs, 3 Codes double inputs, expandable up to 64codes through SEL pin (pin7).Details of Pin connections are shown in the data sheet.
Crystal is connected between the OSCO (Pin8)and OSC1 (Pin9). Output drives a medium power NPN transistor T1 and the IR LEDs connected to its emitter gives pulsed IR rays