The Problem: Powering Smart Plugs Safely at Low Voltage

Smart plugs need compact, low voltage power supplies to operate safely from 230V AC. Without proper design, they can overheat, fail, or drain excess power—not ideal for small, energy-efficient devices.

The Solution: Use a Capacitive Dropper or Compact SMPS

For low-power smart plugs (e.g., 0.5W to 1W), a capacitive dropper circuit is cost-effective and space-saving. For higher power or safer isolation, a miniature SMPS module is preferred. Both options step down 230V AC to a usable DC level like 3.3V or 5V for microcontrollers.

Practical Example: Wi-Fi Smart Plug

Imagine a DIY smart plug using an ESP8266. It needs 3.3V @ ~250mA. Using a 5V SMPS module with an LDO or buck converter works well.

Sample Calculation: Capacitive Dropper Sizing

If your circuit needs 20mA:

• Current = V × 2πfC

• Rearranged: C = I / (2πfV)

• C = 0.02 / (2×3.14×50×230) ≈ 0.28µF

Use a 400V X-rated capacitor for safety.

Product Suggestions: Made in India Components

• SMPS Module

• Capacitor X Rated

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