Glossary for Beginners

This page explains the terms you meet most often in Circzy in everyday language. No need to memorize anything: come back whenever you see an unfamiliar word.

Electronics basics

Circuit

A closed path that electricity flows through: from a power source, through the parts, and back. If the path is broken, no current flows and the parts do not work.

Voltage (V) and current (A)

Voltage is the electrical "push", measured in volts (V). The Arduino Uno works at 5 V, while the ESP32, ESP8266, Pico and STM32 work at 3.3 V. Current is how much electricity flows, measured in amperes (A) or milliamperes (mA).

GND (ground)

The zero point, or "negative side", of a circuit. Every part must share the same GND as the board to work. GND wires are usually black.

VCC, 5V, 3V3

Pins that supply power to parts. 5V gives 5 volts and 3V3 gives 3.3 volts. In the docs, VCC or VDD means a part's power pin.

Resistor

A part that limits current. Most often used to protect LEDs (220 Ω suits most LEDs). Its value is measured in ohms (Ω).

LED

A small light that only works one way round: the long leg (anode, A) toward the pin and the short leg (cathode, C) to GND.

Breadboard

A board full of holes for building circuits without soldering. Holes in one small column are connected, and the long rails along the edges are usually used for power and GND. See Breadboards & Power.

Microcontrollers and boards

Microcontroller

A tiny computer on a single chip. It reads inputs, runs a program and controls outputs. Microcontrollers are inside washing machines, AC remotes, traffic lights and toys.

Board

A ready-made circuit board with a microcontroller plus pins, a power regulator and a USB connector. Examples are the Arduino Uno, ESP32 DevKit and Raspberry Pi Pico. In Circzy, each project uses one board.

Pin

A connection point on the board where parts are attached. Each pin has a number or name, such as 13, A0, GPIO 2 or D4. The number in your program must match the pin you wired.

Digital pin

A pin with only two states: HIGH (on, 5 V or 3.3 V) and LOW (off, 0 V). Used for LEDs, buttons and relays.

Analog pin

A pin that reads values in steps, such as a potentiometer position or light level. On the Arduino Uno the result is a number from 0 to 1023. The Uno's analog pins are named A0 to A5.

PWM

A way to make an output "half on" by switching a pin on and off very quickly. Used to dim LEDs or control motor speed. On the Arduino Uno, PWM pins are marked ~ (3, 5, 6, 9, 10, 11).

Inputs and outputs

Inputs give the board information: buttons, temperature sensors, distance sensors, potentiometers. Outputs take commands from the board: LEDs, buzzers, motors, screens.

Sensor

A part that measures something in the real world, such as temperature (DHT22), distance (HC-SR04), light (LDR) or motion (MPU6050). In Circzy, you can change its value with a slider while the simulation runs.

Actuator

A part that moves or does something: motors, servos, relays, buzzers.

Programs

Program, sketch and code

A program is a list of instructions for the microcontroller. In the Arduino world a program is called a sketch and is written in C++. In Circzy, the sketch is stored as sketch.ino.

Blocks

A way to program without typing: you snap colored command pieces together like a puzzle. Circzy turns the blocks into C++ code automatically. See Block Editor.

setup() and loop()

The two required parts of every sketch. setup() runs once when the board starts, usually to configure pins. loop() then runs over and over; this is where your main logic lives.

delay()

An instruction to wait, in milliseconds. delay(1000) waits 1 second.

Variable

A named "box" that stores a value, such as int temperature = 0;. Its value can change while the program runs.

Library

Ready-made code for a specific part, such as an LCD screen or a DHT22 sensor. Libraries save time because you do not write everything from scratch. See Libraries.

Compiling

Turning human-readable code into firmware that the chip can run. In Circzy, compiling happens automatically when you press ▶. If there is a typo, the Compile Errors panel shows where.

Firmware

The compiled program in a form the microcontroller understands (a .hex or .bin file). On a real board, this firmware is uploaded over USB.

Serial Monitor

A window that shows messages your program sends with Serial.println(), and lets you send text to the board. Very useful for finding mistakes. See Serial Monitor.

Communication and IoT

I²C and SPI

Ways for the board to "talk" to modules such as OLED screens, I²C LCDs or sensors. I²C needs only two data wires (SDA and SCL). The pins differ per board; see Troubleshooting for the list.

WiFi

The ESP32 and ESP8266 have WiFi. In Circzy, the board joins a virtual network called Circzy-WiFi, so you can try web servers, HTTP and MQTT. See WiFi & Virtual Phone.

IoT (Internet of Things)

Everyday things connected to the internet, such as a lamp you switch on from your phone or a weather sensor that sends data to a server.

MQTT

A popular way for IoT devices to exchange short messages over the internet, like a group chat for machines.

Circzy terms