Week 10 Output Devices

Learning Objectives

  • Demonstrate workflows used in controlling an output device(s) with MCU board you have designed.

Hero Shot

1. Introduction

The goal of Week 10 was to add an output device to a microcontroller board I previously designed (Week 6) and program it to do something.
I used my custom ESP32-C3 board and controlled a continuous rotation servo motor using PWM.

2. Determining Power Consumption

For the servo:

  • Voltage: 5V
  • Idle: ~10–15 mA
  • No-load rotation: ~100–150 mA
  • Stall: up to ~700 mA

This showed the servo must run from a 5V supply, not from the ESP32’s 3.3V regulator, and that I needed a 3.3 → 5 V level shifter.

To correctly drive my continuous-rotation servo, I reviewed the manufacturer datasheet. The key specifications I used for my power calculations and PWM programming were taken directly from the sheet.

Key Specifications From Datasheet

  • Operating Voltage: 4.8–6.0 V
  • No-Load Current: ~100–150 mA
  • Stall Current: up to ~700–800 mA
  • Control Signal: Standard PWM (50 Hz)
  • Pulse Width Range: ~1000–2000 μs for full speed

These values guided my design decisions:

  • The servo must be powered from 5 V, not 3.3 V
  • It cannot be powered from the ESP32-C3 regulator
  • The ESP32 PWM (3.3 V logic) must be level-shifted to 5 V

3. Connecting the Servo to My Board

After confirming my ESP32-C3 powered on:

I connected:

  • 5V
  • GND
  • Level-shifted PWM pin

All through the 3×1 header I designed earlier.

4. Programming the Servo

Below is the exact code I used.

#include <ESP32Servo.h>

Servo s;

void setup() {
s.setPeriodHertz(50);
s.attach(8, 500, 2500);
}

void loop() {
s.writeMicroseconds(2000);
delay(3000);
s.writeMicroseconds(1500);
while (true);
}

Explanation

  • setPeriodHertz(50) → standard servo refresh rate
  • attach(8, 500, 2500) → pin + min/max pulse
  • 2000µs → full-speed rotation
  • 1500µs → stop

This confirmed the signal path:

ESP32 3.3V PWM → Level Shifter → Servo Input (5V logic)

5. Working Demo

6. Problems & Fixes

Short between 5V and copper island

Fixed by removing excess solder.

NC pins shorting to GND

Fixed using flux + wick.

7. What I Learned

  • Correctly driving a servo from a custom microcontroller board
  • Level shifting for 5V signals
  • Measuring power consumption
  • PWM control with writeMicroseconds()
  • Debugging shorts and orientation issues
  • Completing the full design → production → programming cycle

8. Group Project

You can check our group project here

9. Files

Download the files