Electrical Components Basics

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i.          Raspberry Pi

The Raspberry Pi is a low cost, credit-card sized computer that plugs into a computer monitor or TV, and uses a standard keyboard and mouse. It is a capable little device that enables people of all ages to explore computing, and to learn how to program in languages like Scratch and Python. It’s capable of doing everything you’d expect a desktop computer to do, from browsing the internet and playing high-definition video, to making spreadsheets, doing word-processing, and playing games.

What’s more, the Raspberry Pi has the ability to interact with the outside world, and has been used in a wide array of digital maker projects, from music machines and parent detectors to weather stations and tweeting birdhouses with infra-red cameras.

In this kit, we use Raspberry Pi as the core controller of driving equipment like DC motor and servo. With the device and a camera collaborated, video data can be acquired in a real-time manner and delivered by Wi-Fi network.

ii.          Step-down DC-DC Converter Module

Built based on the chip XL1509, the module converts the battery output of 7.4V to 5V, so as to supply power to Raspberry Pi and the servo. As a DC to DC converter IC, the chip has an input voltage ranging from 4.5V to 40V and generates an output voltage of 5V with a current of as high as 2A. Please note: only when the input voltage is up to 6.5V, a 5V output can be supported.

iii.          Servo

In this smart car, one servo controls the direction of the car, and the other two, the movement of the camera between X axis and Y axis, thus defining the coverage of the camera. A servo is an automatic control system composed of DC motor, reduction gear set, sensor, and control circuit. It defines the rotation angle of the output shaft via delivering specific PWM signals.

Generally, a servo supports a maximum rotation angle of the shaft (like 180 degrees). It differs from a common DC motor in the rotation mode: a DC motor rotates by circle when a servo rotates in a certain degree and does not rotate in a round circle. Also, the former is used for power supply by its whole-circle rotation, while the latter is applied to controlling the rotation angle of an object (like joints of a robot).

iv.          DC Motor Driver

As the name suggests, the module is used to drive DC motors. The driver is built based on L298N. As a high-voltage and large-current chip for motor driving, encapsulated with 15 pins, the chip has a maximum operating voltage of 46V and an instant peak current of as high as 3A, with an operating current of 2A and rated power of 25W. Thus, it is completely capable of driving two low-power DC motors.

v.          USB Wi-Fi Adaptor

The adapter helps Raspberry Pi connect to a Wi-Fi hot spot.

vi.          Servo Controller

The Servo Controller is built based on PCA9685. PCA9685 is a 16-channel LED controller with I2C bus interface. The resolution ratio of each channel is 12 bits (212=4096 levels). The controller works in a frequency between 40Hz and 1000Hz and its duty cycle can be adjusted in a range of 0 to 100%. It provides PWM signals for the servo and controls the rotation angle of the servo. Meanwhile, the module controls the duty cycle of the square waves output from channel 14 and 15 to regulate the rotational speed of the DC motor, so as to control the speed of the car.

vii.          18650*2 Battery Holder

The battery is to use two 18650 batteries to power the modules and servos on the car.

Note: Please pay attention to the cathode (-) and anode (+) marks inside the holder (near each pole). Install the 18650 batteries accordingly: battery cathode to holder -, and battery anode to holder +.