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internal oscillation circuit, timing circuit, scanning signal generator, key input encoder, instruction decoder,
user code converter, digital modulation circuit and buffer amplifier and so on. It can produce a key scanning
pulse signal, translate the key code, then obtain remote control commands of the keys by telecommand
encoder (remote control encoding pulse). Through pulse amplitude modulation of the 38KHZ carrier signal,
the infrared diode can transmit infrared remote control signal.
In the infrared receiver, photoelectric converter (usually a photodiode or photoelectric triode, here we
use PIN photodiode) converts the received infrared light instruction signal into a corresponding electrical
signal. The received signal is very weak and interference is particularly large, in order to achieve the
accurate detection and signal conversion, in addition to the infrared photoelectric conversion device with
high performance, choosing the reasonable circuit design with good performance is also required. The most
common photoelectric conversion device is a photodiode. When the photosensitive surface of the PN
junction is irradiated by light, the semiconductor material of PN junction absorbs light energy and converts
the light energy into electric energy. When the reverse voltage is added to the photodiode, the reverse
current in the diode will change with the change of the incident light intensity. The larger the radiation
intensity is, the larger the reverse current will be, the reverse current of the photoelectric varies with the
incident light pulse.
In the Hummer-Bot car, the integrated infrared receiving head has three pins, including the power
supply pin, grounding and signal output pin. The circuit is shown in Fig.3.2.35. Ceramic capacitors is a
decoupling capacitor which can filter the output signal interference. The 1 end is the output of the
demodulation signal which is directly connected to the number 2 port on the Arduino. When the infrared
coded signal is transmitted, it will be processed by the infrared joint, then outputs the square wave signal,
and directly supplied to the Arduino, and the corresponding operation is carried out to control the motor.
Figure .3.2.35 Circuit Diagram and Physical Map of Infrared Receiving Head
3.2.5.2 Working Principle
The remote control system in general composed of the remote controller (transmitter), and receiver,
when you press any button on the remote control, it will generate the corresponding encoding pulse and
output various control pulse signals based on the infrared, infrared monitor diode sends the signal to the the
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