ESP32 simulator
An ESP32 DevKit (WROOM and S3), a Raspberry Pi Pico 2 and a LILYGO T-SIM A7670E on the bench, programmed in Arduino C++ in the built-in editor. GPIO, PWM, ADC, I²C, SPI, UART, interrupts, deep sleep, Wi-Fi and LTE drive real circuit parts: sensors, OLED and TFT displays, relays, motor drivers, GPS, a microSD card. The code runs against the circuit solver, so a sensor divider that is wrong gives a wrong reading, a relay coil without a diode spikes, and a board on a flat battery browns out, exactly as on the desk. Wokwi diagrams import straight onto the bench.
Open the labFree, in your browser, no account needed. Part of a free electronics simulator with 293 parts, 193 lessons and 66 builds.
What you can do
- Write the sketch, wire the parts, and read the serial monitor and the scope at the same time.
- See the electrical side the code simulators skip: what the ADC pin actually sees, what the 3.3 V rail does under load.
- Build the GPS tracker, the OLED gadgets and the solar-powered IoT nodes from the course, with their test sheets.
- Bring a Wokwi project in and keep working on it with real battery and power parts.
Builds (3)
ESP32 battery sensor node
Wakes, reads a sensor, reports, sleeps.
LILYGO T-SIM A7670E: an ESP32 and an LTE modem on one board
ESP32-WROVER-E + SIMCom A7670E LTE Cat-1 board: power-on sequence, registration, data context, BAT_ADC.
Motion-activated light
Lights for 30 s when someone passes.
Lessons (30)
SPI bus: MAX7219 display
SPI is the other main serial bus. The master drives a clock (SCK) and shifts data out on MOSI while each device has…
Detecting USB plug-in with an ESP32
A device knows a cable was plugged in by watching VBUS. Divide the 5 V down to a safe level for a 3.3 V GPIO and…
Light sensor with an ESP32
An LDR and a fixed resistor make a voltage divider whose output falls as it gets darker. The sketch reads it on GPIO34…
Wi-Fi and HTTP to the cloud
Connect to the bench access point and POST a JSON message to a server every 10 seconds. This is the last step of every…
Send an SMS with the A7670 LTE module
Cellular modules are driven by AT commands over a serial port. Press the button and the ESP32 tells the A7670 to send…
Capstone: solar-powered GPS tracker
Everything together: a solar panel and charge controller keep a LiFePO4 battery up, a buck converter makes 5 V, the…
Interrupts and debouncing
An interrupt runs a function the instant a pin changes, even while loop() is busy, so no press is ever missed. But a…
Deep sleep and battery life
A battery device spends most of its life asleep. Awake, the ESP32 chip draws about 45 mA; in deep sleep only its…
Settings that survive a reset (NVS)
RAM is wiped every time the chip resets or loses power. To keep a setting, a calibration or a counter, a program…
Watchdog timer
Field devices hang: a sensor stops answering, a network call never returns. A watchdog is a hardware timer the program…
I²C sensor: accelerometer tilt
An accelerometer at rest measures gravity. How the 1 g splits across its x, y and z axes tells you how it is tilted…
I²C sensor: temperature, humidity, pressure
Environmental sensors like the BME280 sit on the I²C bus at a fixed address and return calibrated readings. A library…
PWM actuator: hobby servo
A hobby servo is position-controlled by pulse width, not duty cycle: every 20 ms it expects a pulse between 0.5 ms…
PWM actuator: DC motor through a MOSFET
A GPIO pin gives a few milliamps; a motor wants an amp. A logic-level MOSFET switches the motor’s own supply, and PWM…
Monitoring a supply rail with the ADC
The ESP32’s ADC reads from about 0.15 V to 3.1 V at its default setting, and is only straight up to about 2.45 V. So a…
Blink: your first sketch
Every microcontroller course starts here: setup() runs once, loop() runs forever. digitalWrite() switches a pin…
Analog in, PWM out
analogRead() turns a voltage into a number from 0 to 4095, but the ESP32’s ADC is not a straight line: at its default…
I²C scanner
I²C devices share two wires (SDA, SCL) and each answers to its own 7-bit address. A scanner tries every address and…
16×2 I²C LCD
Show text and numbers on a character LCD over I²C. Here a 12 V adapter feeds an HW-688 for 5 V, the ESP32 reads a pot…
H-bridge: PWM speed, direction and braking
Four switches let current flow through the motor either way. The DRV8833 takes two logic inputs per motor: one high…
ULN2003 driver array for a stepper
An ESP32 pin can give about 20 mA at 3.3 V; a stepper phase wants 100 mA at 5 V. The ULN2003 has seven Darlington…
Bidirectional I²C level shifter (BSS138)
A 3.3 V ESP32 and a 5 V I²C device share a wire that either side may pull low. One BSS138 MOSFET per line does it…
Load-cell scale front end
Four strain gauges on a metal bar form a Wheatstone bridge whose output is a millivolt or two at full load. The HX711…
ADC front end: reference and anti-alias filter
Sampling at 1 kHz can only represent signals below 500 Hz; anything faster (here 3 kHz interference) folds down and…
Strapping pins: when the board will not boot
Five ESP32 pins are read once, as the chip leaves reset, to decide how it starts: GPIO0 (run your program, or wait for…
Arduino Uno: upload your first sketch
An Arduino is a computer on a chip with pins you can switch. It comes with Blink already loaded, so the L LED flashes…
Reading a button: floating inputs and INPUT_PULLUP
A pin set to INPUT with nothing driving it floats: it picks up hum from the room and reads random HIGHs and LOWs…
analogRead and PWM: a pot dims an LED
analogRead turns 0–5 V into a number from 0 to 1023 (10 bits). analogWrite cannot make a real voltage: it switches the…
Powering an Arduino: USB, VIN and the regulator
On USB the board runs from the computer’s 5 V (through a 500 mA fuse on the Uno). On VIN or the barrel jack, the…
Arduino Nano on a breadboard: a servo sweep
The Nano is an Uno shrunk to 45 × 18 mm, with the same ATmega328P. The Servo library makes 50 Hz pulses on any pin…
Parts (40)
Arduino Uno R3 (ATmega328P)
Arduino Uno R3 · ATmega328P 16 MHz, 5 V logic · 32 KB flash (0.5 KB bootloader), 2 KB SRAM, 1 KB…
Arduino Nano (ATmega328P, FT232RL)
Arduino Nano · ATmega328P 16 MHz, 5 V logic · 32 KB flash (2 KB bootloader), 2 KB SRAM, 1 KB…
ESP32 DevKit (ESP32-WROOM-32, AMS1117)
ESP32-WROOM-32 DevKit V1 · 30 pins · 3.3 V logic · VIN 5 V through AMS1117
ESP32-S3 DevKitC-1 (ESP32-S3-WROOM-1, ESP32-S3-WROOM-1-N8R8, SGM2212)
ESP32-S3-DevKitC-1 v1.1 · ESP32-S3-WROOM-1-N8R8 (8 MB flash, 8 MB octal PSRAM) · dual-core 240 MHz…
Raspberry Pi Pico 2 (RP2350A, RT6154A, RP2350)
Raspberry Pi Pico 2 · RP2350A dual Cortex-M33 (or Hazard3 RISC-V) at 150 MHz · 520 KB SRAM · 4 MB…
LILYGO T-SIM A7670E R2 (ESP32-WROVER-E, ESP32)
LILYGO T-SIM A7670E R2 · ESP32-WROVER-E (240 MHz, 4 MB flash, 8 MB PSRAM, Wi-Fi + BLE) · SIMCom…
Orange Pi One
Orange Pi One · Allwinner H3 quad Cortex-A7 1.2 GHz, Mali-400 MP2 · 512 MB DDR3 · boots from…
Coin acceptor
Multi-coin acceptor · DC 12 V ±10 % · 80 mA idle, 250 mA accepting · open-collector COIN output…
Coin slot (₱5 only)
Single-coin validator taught the ₱5 · DC 12 V ±10 % · 80 mA idle, 250 mA accepting ·…
I2C LCD (HD44780, PCF8574)
HD44780 16×2 character LCD · PCF8574 I2C backpack at 0x27 · 5 V · white on blue
MAX7219 8-digit display
MAX7219 LED driver with eight 7-segment digits · SPI write-only: DIN, CLK, CS (load) · 5 V · send…
ILI9341 2.8" TFT (SPI) (MSP2807, MSP2806, XPT2046)
2.8" TFT LCD module, ILI9341 controller, 240 × 320, 65K colours, 4-wire SPI · VCC 3.3–5 V (662K…
1.69" IPS TFT (ST7789) (ST7789V2)
1.69" IPS LCD module, ST7789V2 controller, 240 × 280, 65K colours, 4-wire SPI (write only) · VCC…
OLED display (I²C) (SSD1306, SH1106)
0.96" 128×64, white · SSD1306 · I²C 0x3C
MPU-6050 IMU (GY-521)
GY-521 breakout · 3-axis accelerometer ±2 g and gyro ±250 °/s · I²C at 0x68 · 3.3–5 V, pull-ups on…
BME280 environment sensor
BME280 breakout · temperature ±1 °C, humidity ±3 %, pressure ±1 hPa · I²C at 0x76 · 3.3 V · now 29…
Hobby servo (SG90)
SG90 micro servo · 4.8–6 V · 50 Hz pulses: 0.5 ms = 0°, 1.5 ms = 90°, 2.5 ms = 180° · ~10 mA…
GPS module
u-blox NEO-6M on a GY-NEO6MV2 board · VCC 3–5 V (3.3 V LDO), 3.3 V UART · Open sky · NMEA at 9600…
4G LTE module
SIMCom A7670 LTE Cat-1 board · VIN 5–12 V · UART 3.3 V at 115200 · SIM inserted
MAX485 RS-485 module (MAX485CSA, MAX3485)
MAX485 half-duplex RS-485 transceiver module · 5 V part (works at 3.3 V on the bench, out of spec…
microSD card module (AMS1117, 74LVC125A, FAT32)
Micro SD Card Adapter (AMS1117 + 74LVC125A, 5 V) · 16 GB microSDHC (FAT32)
DS3231 RTC module (ZS-042) (DS3231SN, AT24C32)
DS3231SN real-time clock, ±2 ppm TCXO · AT24C32 EEPROM · CR2032 (3 V lithium, NOT rechargeable)
L298N motor driver
L298N dual H-bridge module · 5–35 V motor supply · 2 A per channel (bipolar Darlington outputs…
DRV8833 motor driver
DRV8833 dual H-bridge breakout · 2.7–10.8 V · 1.5 A per channel (MOSFETs, about 0.36 Ω per side) ·…
INA219 current sensor
INA219 breakout · 0.1 Ω shunt between VIN+ and VIN− in the high side · measures shunt voltage…
ACS712 Hall current sensor (ACS712ELC, ACS712ELC-5A)
ACS712ELC-5A breakout · Hall-effect, isolated from the load path (1.2 mΩ) · OUT = V_CC/2 + 185 mV…
HX711 load-cell ADC
HX711 breakout · 24-bit ADC with a gain-128 bridge amplifier · supplies the bridge excitation (E+…
PAM8403 class-D amp
PAM8403 stereo class-D amplifier board · 2.5–5.5 V · 2 × 3 W into 4 Ω · gain 24 dB (× 16…
Relay module (SRD-05VDC)
1-channel relay board · 5 V coil (SRD-5VDC) with transistor, flyback diode and indicator LED ·…
nRF52832 BLE module
Ebyte E73 (nRF52832) · Bluetooth LE · 1.7–3.6 V · 1.9 µA asleep with the RTC, low-power comparator…
E-paper display 1.54" (SSD1681)
1.54-inch e-paper module (SSD1681) · 200 × 200 · SPI · 3.3 V · draws about 5 mA for 2 s while it…
DS18B20 temperature sensor
DS18B20 digital thermometer · −55 to 125 °C, ±0.5 °C · 1-Wire bus on DQ: needs a 4.7 kΩ pull-up to…
LM35 temperature sensor (LM35DZ)
LM35DZ analog thermometer · output 10 mV per °C (250 mV at 25 °C) · 4–30 V supply · ±0.5 °C · now…
MAX6675 thermocouple module
MAX6675 board with a K-type thermocouple · 0–1024 °C in 0.25 °C steps · SPI read-only: SO, SCK, CS…
PIR motion sensor (SR501)
HC-SR501 passive infrared motion sensor · 4.5–20 V · output 3.3 V HIGH for 3 s after movement…
Ultrasonic distance sensor (SR04)
HC-SR04 ultrasonic ranger · 5 V · send a 10 µs pulse on TRIG; ECHO then goes HIGH for 58 µs per cm…
Hall-effect switch
A3144 unipolar Hall switch · 4.5–24 V · open-collector output pulls LOW while a magnet's south…
Reed switch
Glass reed switch · contacts close when a magnet is near · 0.5 A, 100 V · used in door/window…
Soil moisture sensor
Capacitive soil-moisture probe v1.2 · 3.3–5.5 V · analog output about 2.9 V in dry air falling to…
Microphone amplifier (MAX4466)
Electret microphone with a MAX4466 amplifier · 2.4–5.5 V · output sits at V_CC/2 and swings with…
Calculators
LED resistor calculator
The series resistor for one LED or a string
Voltage divider calculator
Vout from two resistors, or the resistor for a wanted Vout
Also on the lab
Solar PV simulator · Battery and BMS simulator · Arduino simulator · Breadboard simulator · House wiring simulator · PCB layout and perfboard · Brownout backup · Piso Wi-Fi on solar · Questions answered · Compared with other simulators