Electronics Basics: Sensors, Inputs, and Outputs Guide

Basics of Electronics: Sensors & I/O

Understanding Inputs, Outputs, and Digital vs. Analog

The Big Picture: Sense, Think, Act

SENSE (Input): Gathering data from the physical world.

THINK (Process): The microcontroller decides what to do based on logic.

ACT (Output): Changing the physical world (motion, light, sound).

Defining Inputs & Outputs

INPUTS: Signals sent TO the brain (Microcontroller). They measure the environment.

OUTPUTS: Signals sent FROM the brain. They perform actions or display information.

Analog vs. Digital Signals

Digital is ON/OFF (1 or 0). Analog is continuous (range of values).

Digital Sensors: The Simplest Inputs

Reports only two states: HIGH (5V) or LOW (0V).

Examples: Push Buttons, Switches, Reed Switches (Magnetic).

Often requires a 'Pull-up' or 'Pull-down' resistor to ensure a clean signal.

Analog Sensors: Measuring the World

Analog sensors change their RESISTANCE based on the environment. We use a Voltage Divider circuit to read this change as Voltage.

LDR (Light Dependent Resistor): Measures brightness.

Thermistor: Measures temperature.

Potentiometer: Measures rotation (knob).

ADC: Analog to Digital Converter

Microcontrollers are digital (Brain). They don't understand 2.5V. They understand discrete numbers. An ADC translates voltage (0-5V) into a number (e.g., 0-1023).

Basic Outputs: LEDs & Current

An LED (Light Emitting Diode) is the 'Hello World' of electronics.

SAFETY: LEDs have no internal resistance. You MUST use a resistor to limit current.

Control: Write HIGH (5V) to turn on, LOW (0V) to turn off.

High Power Outputs: Transistors

Problem: Microcontrollers are weak. They can only provide ~20-40mA of current. Motors need 500mA+.

Solution: Use a Transistor (or MOSFET). It acts like a digital switch. A tiny signal from the chip controls massive power from a battery.

Analog Outputs? Meet PWM

Digital pins can't output varying voltage (like 2.5V). Instead, we turn the pin ON and OFF very fast. This is Pulse Width Modulation.

Motors & Motion

DC Motors: Spin when power is applied. Swap wires (+/-) to reverse direction.

The H-Bridge: A special chip that contains transistors to let us control motor direction and speed (via PWM) from code.

Application: Distance Sensors

Ultrasonic Sensor (HC-SR04): Works like a bat.

1. Trig pin sends a high frequency sound 'ping'.

2. Sound bounces off object and returns to Echo pin.

3. Distance = (Time x Speed of Sound) / 2

Thinking: Logic Statements

IF (Distance < 10) { Stop Motors; Turn LED ON; } ELSE { Drive Forward; Turn LED OFF; }

The 'IF' statement is the core of robotics. It connects the Sense (Distance) to the Act (Motors).

Visualizing Logic: The Flowchart

Always draw a flowchart BEFORE writing code.

Diamonds = Decisions (Yes/No).

Rectangles = Actions (Turn on LED, Run Motor).

Summary & Challenge

Recap:

1. Sensors (Inputs) can be Digital (Switch) or Analog (Light/Temp). 2. Actuators (Outputs) need drivers (Transistors) for high power. 3. Logic (IF/ELSE) connects them.

Design Challenge:

Design a 'Smart Fan' system. It should turn ON a fan (Motor) when the temperature (Thermistor) gets too hot, but ONLY if someone is in the room (Motion Sensor). Draw the flowchart.