Remote Control Key Matrix Circuit

- Aug 25, 2017-

Remote Control Key matrix circuit

The Block Diagram of Infrared Remote Control Transmitter. It consists of a key matrix, a keying encoder, an instruction encoder, a modulator, a buffer amplifier, a scan generator, a clock pulse generator oscillator, an exciter, and an infrared emitting diode. Where the key encoders, instructions

Encoder, modulator, buffer amplifier, scan generator, clock pulse generator, the oscillator are integrated in the integrated circuit, the patch installed in the handheld transmitter in the printed circuit board, the key matrix circuit with the integrated circuit internal key And the scanning generator is connected with the scanning generator. The working principle of this part circuit is the same as that of the single-chip computer's external key matrix circuit in the remote control system. When the input and output intersections are shorted, the key value corresponding to the key to be pressed will enter the input of the key encoder, and the key value is entered in the key encoder to identify the key bit What command the user publishes to the remote control system).

       Oscillator oscillation frequency by the external ceramic crystal oscillator Zo1 decision, usually Z01 resonant frequency of 455kHz or 48okHz. The oscillation signal all the way through the clock pulse generator frequency, strobe, the clock pulse and about 38kHz carrier frequency signal. The clock pulse is sent to the instruction encoder and the scan generator, and the carrier frequency signal is sent to the modulator. The command code output from the instruction encoder is modulated on the carrier signal. The signal is amplified by the internal buffer amplifier of the integrated circuit and sent out from the integrated circuit to the excitation amplifier circuit of the infrared emission diode. In the handheld infrared remote control transmitter, the oscillation frequency of the oscillator is about 455kHz, it is close to the semiconductor superheterodyne radio frequency, so according to the principle of electromagnetic radiation to determine whether the infrared transmitter oscillator circuit is working properly. The specific practice is to turn on the radio, the band is set in the wave, and set it to the low-end reception frequency (for example, 550kHz), the remote control transmitter near the radio antenna, press the remote control any button, if the radio is loud But the radio does not have any reaction, in the confirmation of the power supply voltage under the premise of normal failure of the ceramic crystal, or poor integrated circuit, maintenance is usually the first change, the first time, Ceramic crystal, if the fault is still, and then for the integrated circuit, because the IC is the use of chip technology welding on the printed circuit board, so replace the Ic is actually replace the entire remote control transmitter circuit board. The output signal from the IC output has been sent to the transistor composed of elements such as infrared light-emitting diode excitation drive amplifier, driven by the transistor V101 amplified output to control the flow to the infrared light-emitting transistor V102 current. When V102 has a forward current flow, the outward radiation is about 932nm infrared is not visible. Infrared light-emitting diode installed in the front of the remote control, shape, with the diode is basically the same positive and negative characteristics, amateur conditions with 47-type multimeter R × 1k block to measure the reverse resistance is infinite, forward resistance of about 30k ohm Gamma. 

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