Introduction to Python and Microcontrollers

Servo Sweep

Make a servo motor sweep continuously from 0° to 180° and back.

New Concepts

• Servo motors
• Driving a servo with PWM angle control

Servo

A servo packages a small DC motor, reduction gears, a position sensor, and control circuitry together, letting you command it to a specific angle (rather than just spinning continuously like the DC motor). Most hobby servos sweep a 180° range via their output “horn,” and can output far more torque than a bare DC motor of similar size.

Controlling a servo with PWM signal

A servo has 3 wires: power (red, VCC), ground (brown, GND), and signal (orange). It’s positioned with a 50Hz PWM signal, where the pulse width (not the duty cycle percentage) determines the angle:

Pulse width	Servo angle
0.5ms	0°
1.0ms	45°
1.5ms	90°
2.0ms	135°
2.5ms	180°

Component List

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Circuit

Servos need a clean 5V supply — double-check polarity before connecting power.

Wiring Diagram

Disconnect all power before building the circuit. Reconnect once verified.

Connections:

• Servo Signal → GPIO21
• Servo VCC → 5V
• Servo GND → GND

Schematic Diagram

Code

File: 04_output/code/Servo_Sweep.py Module: 04_output/code/myservo.py

from myservo import myServo
import time

servo=myServo(21)#set servo pin
servo.myServoWriteAngle(0)#Set Servo Angle
time.sleep_ms(1000)

try:
    while True:       
        for i in range(0,180,1):
            servo.myServoWriteAngle(i)
            time.sleep_ms(15)
        for i in range(180,0,-1):
            servo.myServoWriteAngle(i)
            time.sleep_ms(15)        
except:
    servo.deinit()

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How to Run

Online

1. Open Thonny → 04_output/code/.
2. Right-click myservo.py → Upload to / — wait for it to finish uploading to the ESP32-S3.
3. Double-click Servo_Sweep.py.
4. Click Run current script — the servo sweeps from 0° to 180° and back, repeatedly.

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Code Explanation

Create the servo object and set a starting angle

servo=myServo(21)
servo.myServoWriteAngle(0)
time.sleep_ms(1000)

myServo(21) configures PWM on GPIO21 at the servo’s expected 50Hz. Setting it to 0° first and waiting a second gives the servo time to physically reach that position before the sweep starts.

Sweep up, then down

for i in range(0,180,1):
    servo.myServoWriteAngle(i)
    time.sleep_ms(15)
for i in range(180,0,-1):
    servo.myServoWriteAngle(i)
    time.sleep_ms(15)

Each loop steps the angle one degree at a time with a short pause, producing a smooth sweep rather than an instant jump (the same “ramp gradually” idea as Breathing LED’s PWM fade, just applied to angle instead of brightness).

Release the servo

except:
    servo.deinit()

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Key Concepts

• PWM pulse width vs. duty cycle: most PWM uses described so far (LED brightness, motor speed) care about duty cycle percentage; servos instead care about the absolute pulse width in milliseconds, at a fixed 50Hz frequency
• myServoWriteAngle(pos): converts a 0–180° angle into the correct underlying duty cycle, so application code never has to do that pulse-width math directly
• Smooth motion via small steps: sweeping one degree at a time with a short delay, rather than jumping straight to the target angle, is the same incremental-change pattern used throughout this kit (breathing LEDs, gradient colors, motor speed ramps)

See class myServo for the full API reference.

Further Exploration

• Change the step size (e.g. range(0,180,5)) for a faster, choppier sweep.

Back to Module

Adapted from Python_Tutorial.pdf Project 18.1

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