SunFounder Thales Kit, Руководство пользователя

Страница: 34 / 167

SunFounder Thales Kit for Raspberry Pi Pico, Release 1.0
Example
Intruder Alarm
Custom Tone
2.2.15 Servo
A servo is generally composed of the following parts: case, shaft, gear system, potentiometer, DC motor, and embed-
ded board.
It works like this: The microcontroller sends out PWM signals to the servo, and then the embedded board in the servo
receives the signals through the signal pin and controls the motor inside to turn. As a result, the motor drives the
gear system and then motivates the shaft after deceleration. The shaft and potentiometer of the servo are connected
together. When the shaft rotates, it drives the potentiometer, so the potentiometer outputs a voltage signal to the
embedded board. Then the board determines the direction and speed of rotation based on the current position, so it
can stop exactly at the right position as defined and hold there.
The angle is determined by the duration of a pulse that is applied to the control wire. This is called Pulse width
Modulation. The servo expects to see a pulse every 20 ms. The length of the pulse will determine how far the motor
turns. For example, a 1.5ms pulse will make the motor turn to the 90 degree position (neutral position). When a
pulse is sent to a servo that is less than 1.5 ms, the servo rotates to a position and holds its output shaft some number
of degrees counterclockwise from the neutral point. When the pulse is wider than 1.5 ms the opposite occurs. The
minimal width and the maximum width of pulse that will command the servo to turn to a valid position are functions
of each servo. Generally the minimum pulse will be about 0.5 ms wide and the maximum pulse will be 2.5 ms wide.
30 Chapter 2. What is Included in This Kit