Arduino, running the sketch you wrote
arduino-cli compiles it, an AVR8 core executes it instruction by instruction, and the LCD shows what the ATmega328P actually put on the bus. Uno, Nano, Mega and ATtiny85, no board on your desk.

Hardware is all about iteration. Velxio lets you wire a circuit, program the board and run it in seconds, real firmware on a real solver, right in the browser.
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Nothing on this page is a scripted animation: the firmware is compiled and executed, and the circuit around it is solved.
arduino-cli compiles it, an AVR8 core executes it instruction by instruction, and the LCD shows what the ATmega328P actually put on the bus. Uno, Nano, Mega and ATtiny85, no board on your desk.

arduino-cli or ESP-IDF compiles the sketch, then AVR8, RP2040, RISC-V, Xtensa or ARM executes it instruction by instruction. What the OLED draws and what the serial monitor prints is what the chip actually did.

ngspice compiled to WebAssembly runs a full nodal analysis about 60 times a second. GPIO pins drive real nets, ADC inputs read solved node voltages, and probes report RMS, DC and current wherever you drop them.

Adders, comparators, decoders, flip-flops and a 1-bit ALU slice: no microcontroller anywhere, just gates, switches and LEDs solved as a real net. The classroom half of electronics, without the breadboard.

The M5Stack Cardputer with its keyboard, Seeed's round display keeping time, Pimoroni's Badger 2350 driving e-paper, and DFRobot's UNIHIKER M10 in the catalogue alongside them. Their makers sent the hardware so the emulation could be checked against the real thing.




35 boards across 6 CPU architectures — AVR8, ARM Cortex-M, ARM Cortex-A, RISC-V, Xtensa, and Linux. Including partner boards from Pimoroni, M5Stack, Seeed Studio and DFRobot. All running locally, no cloud needed.
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Private projects, BOM and schematic exports, GitHub Sync and the offline desktop app, for everyone enrolled.
Billed once to your institution, per semester or per year. Volume pricing on request for large cohorts.
Arduino, ESP32, RP2040, STM32, ATtiny and Raspberry Pi, with SPICE analog solved alongside the firmware. Not a sandboxed mock.
The simulator stays free forever, WiFi with internet included. Paid plans unlock the Linux and STM32 boards, custom WiFi networks, the local network gateway and the offline desktop app. Maker and Pro add the AI agent; No AI leaves it out.
Discover the simulator + light AI help.
The full workbench, zero AI. You write every line.
For makers shipping real circuits with AI help.
Private projects, GitHub Sync and BOM exports.
Questions, bugs and ideas: the Discord and the issue tracker are open, and so is every line of the simulator.
An interactive Arduino Uno circuit simulation you can run free in your browser on Velxio, by alexis-pal.
#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <DHT.h>
#include <SoftwareSerial.h>
// Configuration du module Bluetooth sur les broches 10 (RX) et 11 (TX)
SoftwareSerial mySerial(11, 10); // RX, TX
// Configuration du capteur DHT22 sur la broche 8
#define DHTPIN 8
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);
// Configuration de l'écran LCD I2C (Adresse 0x27, 16 colonnes, 2 lignes)
LiquidCrystal_I2C lcd(0x27, 16, 2);
void setup() {
Serial.begin(115200);
mySerial.begin(9600); // Vitesse standard pour la plupart des modules Bluetooth HC-05 / HC-06
// Initialisation du capteur DHT
dht.begin();
// Initialisation de l'écran LCD
lcd.init();
lcd.backlight();
// Configuration des broches de sortie
pinMode(6, OUTPUT); // LED Rouge
pinMode(5, OUTPUT); // LED Verte
pinMode(10, OUTPUT); // Relais / Moteur
delay(2000);
lcd.clear();
}
void loop() {
// Lecture des données du capteur
float humidity = dht.readHumidity();
float temperature = dht.readTemperature();
// Vérification si la lecture a échoué
if (isnan(humidity) || isnan(temperature)) {
Serial.println("Erreur de lecture DHT");
lcd.setCursor(0, 0);
lcd.print("Erreur Capteur ");
lcd.setCursor(0, 1);
lcd.print(" ");
} else {
// Affichage sur l'écran LCD
lcd.clear();
lcd.setCursor(0, 0);
lcd.print("H: ");
lcd.print(humidity);
lcd.print("%");
lcd.setCursor(0, 1);
lcd.print("T: ");
lcd.print(temperature);
lcd.print((char)223);
lcd.print("C");
// Envoi des données par Bluetooth vers le téléphone
mySerial.print("Humidite: ");
mySerial.print(humidity);
mySerial.print("% | ");
mySerial.print("Temperature: ");
mySerial.print(temperature);
mySerial.println(" C");
}
// Logique de contrôle de l'humidité (> 70%) -> LED Rouge (pin 6)
if (humidity > 70) {
digitalWrite(6, HIGH);
} else {
digitalWrite(6, LOW);
}
// Logique de contrôle de la température (>= 26°C) -> LED Verte (pin 5) & Relais (pin 10)
if (temperature >= 26) {
digitalWrite(5, HIGH);
digitalWrite(10, HIGH); // Active le relais / moteur
} else {
digitalWrite(5, LOW);
digitalWrite(10, LOW); // Désactive le relais / moteur
}
delay(2000); // Attente de 2 secondes avant la prochaine lecture
}