Logic Gates & Circuit Basics

1. Basic Electrical Concepts

Voltage (V): Electrical pressure or potential difference.
Current (I): Flow of electrons in a circuit, measured in Amperes (A).
Resistance (R): Opposition to current flow, measured in Ohms (Ω). V = I * R (Ohm’s Law)
Power (P): Energy used by a device: P = V * I

Logic gates are the building blocks of digital electronics. They process one or more input signals and produce an output according to a logical rule.

Gate	Symbol	Inputs	Output	Boolean Expression	Example Use
AND	&	2	1	A·B	Motor ON only if two switches pressed
OR	≥1	2	1	A + B	Light ON if either sensor triggers
NOT	¬	1	1	¬A	Inverts signal
NAND	↑	2	1	¬(A·B)	Safety circuits
NOR	↓	2	1	¬(A + B)	Alarm systems
XOR	⊕	2	1	A⊕B	Toggle circuits, e.g., lamp ON if only one switch is pressed

Once you understand logic gates, you can implement them using microcontrollers like Arduino or ESP32.

Use GPIO pins as digital inputs and outputs (HIGH/LOW) corresponding to logic 1/0.
Combine sensors and buttons using AND, OR, and NOT logic to control LEDs, motors, or relays.
Use resistors for pull-up/pull-down configurations to stabilize input pins.
Understand series and parallel circuits for multiple components.
Start with simple LED + button circuits and gradually add sensors and actuators.

LED blink using Arduino or ESP32
AND gate with two buttons → LED lights up only if both pressed
OR gate with motion sensors → Alarm triggers if any sensor detects motion
Temperature sensor + fan → Fan ON if temperature > threshold AND humidity > threshold