Arduino Hands-On Programming and Robotics Course

📘 Lesson F10 – Power Supply and Safety Basics

🎯 Learning Objectives

After completing this lesson, students will be able to:

✅ Understand what electrical power is

✅ Understand Voltage, Current, and Power

✅ Understand how Arduino gets power

✅ Understand different power supply methods

✅ Understand battery types used in Arduino projects

✅ Calculate basic power requirements

✅ Identify common power-related problems

✅ Protect Arduino and components from damage

✅ Follow electrical safety practices in projects

1. Introduction

Every electronic device requires power to operate.

Examples:

Mobile Phones
Laptops
Televisions
Robots
Arduino Boards

Without power, electronic circuits cannot function.

In Arduino projects, understanding power supply is extremely important because most beginner problems are related to incorrect power connections.

Many Arduino boards are damaged due to:

Wrong voltage
Reverse polarity
Overcurrent
Short circuits

Therefore, before building projects, students must understand power and safety fundamentals.

2. What is Electrical Power?

Electrical power is the rate at which electrical energy is used.

Power allows electronic devices to perform work.

Examples:

Lighting an LED
Rotating a Motor
Running a Sensor
Operating a Relay

Without power, none of these devices can function.

3. Basic Electrical Quantities

There are three fundamental electrical quantities every Arduino student must know.

Voltage (V)

Current (I)

Power (P)

These form the foundation of electronics.

4. What is Voltage?

Voltage is the electrical pressure that pushes current through a circuit.

Think of voltage like water pressure inside a pipe.

Higher pressure pushes water harder.

Similarly:

Higher voltage pushes electrons through a circuit.

Unit of Voltage

Voltage is measured in:

Volts (V)

Examples:

1.5V Battery
5V Arduino
9V Battery
12V Adapter

Water Tank Example

Imagine a water tank placed on a roof.

The higher the tank:

The higher the water pressure.

Similarly:

Higher voltage means higher electrical pressure.

5. What is Current?

Current is the flow of electrons through a circuit.

Think of current as the amount of water flowing through a pipe.

Unit of Current

Measured in:

Ampere (A)

Commonly:

mA (Milliampere)
A (Ampere)

Examples

LED:

20mA

Servo Motor:

200mA–1000mA

Arduino Uno:

Approximately 50mA

6. What is Power?

Power is the rate at which electrical energy is consumed.

It tells us how much work a device can perform.

Power Formula

$P=V×IP=V\times I$

Where:

P = Power (Watts)

V = Voltage (Volts)

I = Current (Amperes)

Example

Voltage = 5V

Current = 1A

Power:

P = 5 × 1

P = 5 Watts

7. What is a Power Supply?

A power supply is a device that provides electrical energy to a circuit.

Examples:

USB Port
Battery
Adapter
Power Bank

All Arduino projects require a power source.

8. Powering Arduino UNO

Arduino Uno can be powered using multiple methods.

Method 1: USB Cable

Most common method.

Connection:

Computer

↓

USB Cable

↓

Arduino

Provides:

5V

Advantages:

✔ Easy

✔ Safe

✔ Suitable for learning

Method 2: DC Barrel Jack

Arduino Uno contains a DC power jack.

Recommended Input:

7V – 12V

Examples:

9V Adapter
12V Adapter

The onboard regulator converts it to 5V.

Method 3: VIN Pin

External voltage can be supplied through VIN.

Recommended:

7V – 12V

Used in battery-powered projects.

Method 4: 5V Pin

Regulated 5V can be supplied directly.

⚠ Warning:

Never connect more than 5V.

Doing so may permanently damage the Arduino.

9. Understanding Arduino Power Pins

VIN

Voltage Input

Used for:

7V–12V external power.

5V

Provides regulated 5V.

Used for sensors and modules.

3.3V

Provides 3.3V output.

Used for low-voltage modules.

GND

Ground reference.

Every circuit must share a common ground.

10. Common Batteries Used in Arduino Projects

AA Battery

Voltage:

1.5V each

Example:

4 Batteries

9V Battery

Easy to use.

Suitable for small projects.

Not suitable for motors.

18650 Lithium Battery

Most common in robotics.

Voltage:

3.7V nominal

4.2V fully charged

Li-ion Battery Pack

Used in:

Robots
Drones
Portable Systems

11. Why Motors Need Separate Power

Many beginners connect motors directly to Arduino.

This causes problems.

Motors require high current.

Example:

Servo Motor:

500mA+

DC Motor:

500mA–2A

Arduino cannot safely provide this current.

Result

Arduino may:

Restart
Freeze
Behave unpredictably

Correct Method

Battery

↓

Motor Driver

↓

Motor

Arduino should only provide control signals.

12. Common Power Problems

Problem 1: Arduino Not Turning ON

Possible Causes:

Loose cable
Dead battery
Wrong adapter

Problem 2: Arduino Resetting Repeatedly

Possible Causes:

Insufficient current
Motor overload
Weak battery

Problem 3: Sensor Readings Changing Randomly

Possible Causes:

Poor grounding
Power fluctuations

Problem 4: Upload Errors

Possible Causes:

USB cable issue
Power instability

13. What is a Short Circuit?

A short circuit occurs when:

Positive (+)

directly touches

Ground (-)

without a load.

Example

5V Wire

↓

Directly connected to

↓

GND

Results

Excess current
Heat generation
Component damage
Fire risk

14. What is Reverse Polarity?

Reverse polarity occurs when:

Positive and negative terminals are swapped.

Example:

Battery connected incorrectly.

Effects

Circuit malfunction
Component damage
Permanent failure

Always check polarity before powering a circuit.

15. Importance of Common Ground

All components in a project must share the same ground reference.

Example:

Arduino

↓

Motor Driver

↓

Sensor

↓

Battery

All GND connections should be connected together.

What Happens Without Common Ground?

Sensors behave unpredictably
Motors malfunction
Communication errors occur

16. Electrical Safety Rules

Rule 1

Always power OFF before changing wiring.

Rule 2

Check polarity before connecting batteries.

Rule 3

Never connect 12V directly to Arduino 5V pin.

Rule 4

Never short power and ground.

Rule 5

Use proper wire connections.

Rule 6

Do not touch exposed AC mains wiring.

Rule 7

Use recommended voltages only.

Rule 8

Read sensor datasheets when required.

17. Real-World Example

Obstacle Avoiding Robot

Components:

Arduino Uno
Ultrasonic Sensor
L298N Motor Driver
DC Motors
Battery Pack

Power Flow:

Battery

↓

L298N Driver

↓

Motors

↓

Arduino receives control power

This prevents Arduino from being overloaded.

18. Power Distribution in Projects

A good project separates:

Logic Power

For:

Arduino
Sensors

Load Power

For:

Motors
Pumps
Relays

This increases reliability.

19. Best Practices

✅ Use quality batteries

✅ Use common ground

✅ Check wiring twice

✅ Power motors separately

✅ Use correct voltage

✅ Avoid loose wires

✅ Keep circuits organized

✅ Disconnect power when not in use

📊 Arduino UNO Recommended Voltage Table

Source	Voltage
USB	5V
5V Pin	5V
VIN	7V–12V
DC Jack	7V–12V
3.3V Pin	3.3V

📊 Summary

In this lesson, we learned:

✅ Voltage

✅ Current

✅ Power

✅ Power Supply Methods

✅ Arduino Power Pins

✅ Batteries

✅ Common Ground

✅ Short Circuits

✅ Reverse Polarity

✅ Safety Rules

Understanding power and safety is one of the most important skills in electronics because incorrect power connections can damage components and create safety hazards.

📖 Key Terms

Voltage

Electrical pressure.

Current

Flow of electrons.

Power

Electrical energy consumption rate.

Ground (GND)

Reference point in a circuit.

VIN

Voltage input pin.

Short Circuit

Direct connection between power and ground.

Reverse Polarity

Swapping positive and negative connections.

Power Supply

Device that provides electrical energy.

🎯 Quiz

1. What is the recommended voltage range for Arduino UNO VIN?

A. 3V–5V

B. 5V–6V

C. 7V–12V ✅

D. 15V–20V

2. What does GND stand for?

A. Generator

B. Ground ✅

C. Grid Node

D. Gain

3. Which formula calculates power?

A. V = I × R

B. P = V × I ✅

C. I = V/R

D. R = V/I

4. Why should motors not be powered directly from Arduino?

A. Motors need higher current ✅

B. Motors need internet

C. Motors use analog pins

D. None of these

5. What is a short circuit?

A. Low voltage

B. Direct connection between power and ground ✅

C. High resistance

D. Broken wire

🏠 Assignment

Task 1

List all methods of powering Arduino Uno.

Task 2

Create a table of common batteries used in Arduino projects.

Task 3

Draw a power distribution diagram for an obstacle-avoiding robot.

Task 4

Explain the importance of common ground with an example.

Task 5

List ten electrical safety rules that every Arduino developer should follow.