Dev Board (Arduino / ESP32 / RPi)
Module
A ready-made board with an MCU, power, USB and broken-out pins so you can prototype without designing a circuit board. The fastest way to start building.
What it looks like
Dev Board (Arduino / ESP32 / RPi)
A typical module — exact shape, colour and markings vary between manufacturers.
Types & variants
Key specs
MCU / SoC
-The chip and core (AVR, ESP32, RP2040, ARM, etc.).
Logic voltage
V3.3V (most) or 5V (Uno) - match your sensors/level shift.
GPIO / ADC / PWM
-Usable pins and analog/PWM channels.
Connectivity
-USB, Wi-Fi, Bluetooth, sometimes Ethernet.
Power input
VUSB and/or VIN range; check the onboard regulator.
Laws that govern it
- Ohm's lawV = I × R
Per-pin and total current limits, pull-up values, LED resistors — nearly every hardware mistake on a dev board is an Ohm's law mistake.
- Watt's lawP = V × I = I²R = V²/R
The onboard regulator drops (Vin − 5 V) × I as heat, which is why powering servos from the barrel jack browns the board out.
- Law of capacitance — capacitance formula Q = CVQ = C × V, i = C·dv/dt, E = ½CV²
Decoupling and bulk capacitance handle the current spikes of WiFi transmit bursts — the usual cure for an ESP32 that reboots when it connects.
- Kirchhoff's voltage law (KVL)ΣV(loop) = 0
Mixing 5 V and 3.3 V parts means divider or level-shifter loops; getting that arithmetic wrong is how GPIO pins die.
Each law is stated in full — with its diagram, variables and worked meaning — on the electrical laws page.
Markings
Board silkscreen labels every pin (Dx, Ax, GPIOxx, 3V3, 5V, GND). Pinout diagrams ('pinout cards') online.
Standard values
Uno, Nano, ESP32 DevKit, ESP8266 NodeMCU, Pi Pico/Pico W, STM32 Blue Pill, Pi 4/5.
How to choose
Pick by connectivity (need Wi-Fi -> ESP32), pin count, logic voltage, ecosystem (Arduino vs MicroPython vs Linux) and community support. Use 3.3V boards with 3.3V sensors or add level shifting.
Pinout & package
Header rows of GPIO with power (3V3/5V/GND) and USB. Note 5V (Uno) vs 3.3V (most) logic; some pins are input-only or strapping pins (ESP32).
Example circuits
- Blink an LED (hello-world)
- Read a sensor and send to a phone over Wi-Fi (ESP32)
- Drive a servo/motor via a driver
- Data logger to SD/cloud
Common failures
Fried pin/board from over-voltage or shorting 5V to a 3.3V pin; bad USB cable (power-only) blocks upload; brown-out from underpowered USB; bootloader/driver issues.
How to test
Plug in USB, upload a blink sketch. Check the onboard 3V3/5V rails and that the port enumerates. No upload = cable, driver, or hold-boot-button (ESP).
Substitutes
Same family/footprint (Nano clones, ESP32 variants). Switching ecosystems means re-writing/porting code; check pin and voltage compatibility.