Arduino

Voltage and Power Traps

• 3.3V vs 5V logic mixing damages boards — ESP32 is 3.3V, Uno is 5V, level shifter required
• USB provides max 500mA — not enough for motors, servos, or many LEDs
• Never power motors from Arduino 5V pin — use external supply with common ground
• Brown-out causes random resets — looks like code bugs, actually insufficient power
• Decoupling capacitors (0.1µF) near sensor power pins — reduces noise-related glitches

Wiring Mistakes

• Floating inputs read random values — always use pullup or pulldown resistor
• All components must share common ground — separate grounds = nothing works
• Long wires pick up noise — keep analog sensor wires short
• LEDs need current limiting resistors — direct connection burns LED and pin
• Reversed polarity destroys components — double-check before powering on

Pin Conflicts

• RX/TX pins (0, 1) conflict with Serial — avoid for GPIO when using Serial Monitor
• Some pins have special functions — check board pinout for I2C, SPI, interrupt-capable pins
• PWM only on pins marked with ~ — analogWrite() on wrong pin does nothing
• Internal pullup available — INPUT_PULLUP eliminates external resistor for buttons