Subtitle: Building the foundation for humanoid robots — understanding electricity, batteries, motors, and torque.

Electronics for Robotics

Why Electronics Matters

A humanoid robot is made of:

• Brain → Computer/Microcontroller
• Muscles → Motors
• Eyes → Cameras and Sensors
• Nervous System → Electronics and Wiring
• Skeleton → Mechanical Structure

Before learning motors and robots, we need to understand electricity. Electronics form the nervous system that connects every part of the robot, enabling power delivery, signal processing, and precise control.

Relationship Between Them

The most important equation in beginner electronics:

Where:

• V = Voltage
• I = Current
• R = Resistance

You will use this for the rest of your robotics career.

Robotics Example

Suppose:

• Battery = 12V
• Motor current = 2A

Then:

Homework 1 (No Hardware Needed)

1. Q1 A battery provides: 12V, 3A. How much power?
2. Q2 What is the difference between Voltage, Current, and Resistance? Explain in your own words.
3. Q3 Why can't a tiny phone battery directly power a large industrial motor?

Batteries, Motors, and Torque (Robot Muscles)

Part 1: Why Robots Need Batteries

A robot cannot plug itself into a wall while walking. It needs stored energy. A battery stores electrical energy and supplies it to:

• Controllers
• Sensors
• Cameras
• Motors

The motors consume the most power.

Part 2: Battery Capacity (mAh)

You often see batteries labeled: 1000 mAh, 2000 mAh, 5000 mAh.

mAh means: milliampere-hour

Example: A 2000 mAh battery can theoretically provide:

• 2000 mA for 1 hour
• 1000 mA for 2 hours
• 500 mA for 4 hours

This is an approximation because real batteries are not 100% efficient.

Part 3: Types of Batteries Used in Robotics

1. AA Batteries
   Advantages: Cheap, Safe, Good for learning
   Disadvantages: Low power, Not suitable for large robots
2. Lithium-Ion Batteries
   Used in: Laptops, Power banks, Electric tools
   Advantages: High energy density, Rechargeable
3. LiPo (Lithium Polymer)
   Used in: Drones, Advanced robots, RC vehicles
   Advantages: Very high current output
   Disadvantages: Must be handled carefully
   Many advanced robots use LiPo packs.

Part 4: Motors = Robot Muscles

Without motors, a robot cannot move. There are four major motor types:

• DC Motor
  Simple motor. Apply voltage → it spins.
  Used in: Toy cars, Small robots
  Advantages: Cheap, Easy
  Disadvantages: Doesn't know its position
• Servo Motor
  A servo can move to a specific angle (e.g., 0°, 90°, 180°).
  Used in: Robot arms, Small humanoids
  Example: SG90 Servo
• Stepper Motor
  Moves in precise steps.
  Used in: CNC machines, 3D printers
  Advantages: Very accurate
• BLDC Motor
  BLDC = Brushless DC Motor
  Used in: Drones, Electric vehicles, Professional robots
  Advantages: Powerful, Efficient, Long life
  Many modern humanoids use BLDC motors.

Part 5: Torque (Very Important)

Suppose you try to open a tight nut. You use a long wrench because it provides more turning force. That turning force is called Torque.

In robotics:

• Speed = How fast the motor rotates
• Torque = How strong the motor is

A 70 kg humanoid requires a lot of torque.

Example:

• A toy motor: High speed, Low torque → Can spin quickly but cannot lift a brick.
• A heavy-duty motor: Lower speed, High torque → Can lift heavy objects.

Why Your Future Humanoid Depends on Torque

For lifting 70 kg, we care about:

• Shoulder torque
• Elbow torque
• Hip torque
• Knee torque

The knee joint will be one of the most demanding joints in the entire robot.

Homework

1. Q1 Which battery type is commonly used in drones?
2. Q2 Which motor is commonly used in small robot arms?
3. Q3 What is more important for lifting 70 kg: High speed or High torque?
4. Q4 A 3000 mAh battery powers a device drawing 1000 mA continuously. Approximately how many hours will it run?