🔍 The Problem :

Reverse polarity—when power supply wires are connected the wrong way—can instantly damage sensitive IoT circuits. Many IoT devices use 3.3V or 5V logic, and a reverse connection could fry microcontrollers, sensors, or communication modules.

✅ The Solution :

A simple yet effective fix is using a MOSFET-based reverse polarity protection circuit. Unlike regular diodes that waste power through voltage drop, a P-channel MOSFET placed on the high side allows current to flow only when polarity is correct—with minimal loss.

📱 Practical Example :

Imagine powering your ESP32-based home automation board. If a 12V adapter is accidentally reversed, the ESP32 could be permanently damaged. Adding a P-MOSFET (e.g., IRF9540) between the adapter and circuit ensures it only conducts when the voltage is correctly applied.

🔢 Sample Calculation :

To size the gate pull-down resistor:

If Vgs(th) = -2V and Vin = 12V, use a 10kΩ resistor from gate to ground.

This ensures the MOSFET stays off if power is reversed and quickly turns on when correct polarity is applied.

🛠️ Product Suggestion :

Find high-quality, Made in India:

🔌 MOSFET

📏 Resistor Kit

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