Introduction: ⚡ How to Auto Change 220W Mini Inverter When Electricity Is Gone | Auto Load Turn-On System

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About: Hi, I'm Estiak Khan, a B.Sc. engineer in Electrical and Electronic Engineering (EEE), a DIY electronics enthusiast, and a content creator. I specialize in Arduino, PIC microcontrollers, IoT automation, and pow…

Are you tired of manually switching to backup when the power goes out?

Looking for a smart, automatic system that powers your mini inverter, WiFi router, or DC appliances when electricity fails?

This blog shows you how to build a Mini DC IPS Auto Load Changeover Circuit that:

  1. Automatically switches from AC adapter to battery when power cuts
  2. Turns on your load instantly without delay
  3. Works for inverters up to 220W and other 12V devices

Let’s dive in! 👇

Supplies

Components List (Serial-Wise)

  1. Relay – SRD-05VDC-SL-C (5V SPDT Relay)
  2. Diode D1 – 1N4007 (Relay coil protection)
  3. Diode D2 – 6A10 (High current reverse protection)
  4. Resistor R1 – 1kΩ (for LED2 – Power Indicator)
  5. Resistor R2 – 1kΩ (for LED1 – Battery Indicator)
  6. Resistor R3 – 1kΩ (for LED3 – NO Mode Indicator)
  7. LED1 – 5mm Red LED (Battery mode – NC)
  8. LED2 – 5mm Red LED (Power adapter indicator)
  9. LED3 – 5mm Red LED (NO Mode Active)
  10. DC Power Socket – 5.5mm barrel jack (12V Adapter)
  11. Battery Connector – 2-pin terminal block (12V Battery)
  12. NC Output Connector – 2-pin terminal block (Battery Load)
  13. NO Output Connector – 2-pin terminal block (Adapter Load)
  14. PCB or Breadboard – Assembly base
  15. Jumper Wires – For connections

Step 1: 🧠 Circuit Working Principle

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This system uses a 5V relay to detect whether the 12V adapter is providing power. When electricity is available:

  1. Relay coil is energized
  2. Load is connected to the adapter via the Normally Open (NO) contact
  3. When electricity is gone:
  4. Relay becomes de-energized
  5. Load automatically switches to battery power via the Normally Closed (NC) contact

This transition is instant and automatic with no switch needed.

Step 2: 🔄 Detailed Circuit Diagram Explanation


At the heart of the system is a 5V SPDT Relay (SRD-05VDC-SL-C), which acts as a smart switch between two power sources — a 12V DC adapter and a 12V battery. The adapter's 12V line powers the relay coil (between Pin 2 and Pin 5), which switches the load from battery (NC) to adapter (NO) when energized.

A 1N4007 diode (D1) is placed across the relay coil to prevent voltage spikes when switching, protecting the relay from damage. Another high-current 6A10 diode (D2) is placed in series with the adapter line to prevent back current and reverse polarity issues.

When the adapter is powered:

  1. The relay is energized
  2. Common contact (Pin 3) connects to NO (Pin 1)
  3. Load receives power from the adapter

When the adapter fails:

  1. The relay de-energizes
  2. Common contact switches to NC (Pin 4)
  3. Load is powered from the battery instantly

There are 3 LED indicators:

  1. LED2 shows adapter (power) status
  2. LED1 shows battery mode (NC active)
  3. LED3 shows NO mode (adapter powering the load)

Each LED is in series with a 1kΩ resistor for current limiting.

Step 3: 🔋 Real-Life Use Case


Suppose you're running a 220W mini inverter, WiFi router, or LED light system.

✅ When electricity is ON → Load runs via adapter

✅ When electricity fails → Load switches instantly to battery

✅ No user action, no flicker, no downtime

Perfect for:

  1. WiFi Routers
  2. Smart Home Devices
  3. Mini Inverters
  4. Microcontroller Boards (Arduino, ESP, etc.)


Step 4: 🎥 YouTube Video Overview

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🔌 Auto Load Switch Circuit for 12V DC Devices 🔋
🔧 Live Load Test
🔋 Works with Mini Inverter, Router
📡 Automatic Switchover System
📍 Subscribe: EST Experiments

Step 5: 📝 Final Thoughts


This Auto Load Changeover System is simple, cost-effective, and powerful. It guarantees uninterrupted power for essential devices using a basic relay and few components.

Whether you're a DIYer, student, or electronics enthusiast, this circuit is a must-have tool for your home backup setup.