🔋 DIY Automatic Load On/Off Mini DC IPS Making at Home

🧰 Components Required

Component Quantity

• LM317 Voltage Regulator
• 1N5399 Diodes
• SRD-05VDC-SL-C Relay
• 4700µF Capacitor
• 47pF Capacitor
• 1kΩ Resistors
• 338Ω Variable Resistor (RP1)
• LED Indicators (5mm)
• Battery Connector
• Load Connector
• DC Barrel Jack

🔧 Features

✅ Automatic load ON/OFF based on battery voltage

• ✅ Automatic load ON/OFF based on battery voltage

✅ Adjustable output voltage via LM317

• ✅ Adjustable output voltage via LM317

✅ Charge a12V lead-acid battery safely

• ✅ Charge a12V lead-acid battery safely

✅ LED indicators for charging and load status

• ✅ LED indicators for charging and load status

✅ Compact, single-layer PCB design

• ✅ Compact, single-layer PCB design

🖥️ Schematic Diagram

This schematic shows how the LM317 regulates voltage and controls a relay to automatically switch the connected load based on battery level.

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📦 PCB Files

Download the Gerber File:

👉 Click to Download Gerber ZIP

🧾 PCB Design

To ensure reliability and compactness, a single-layer PCB was designed for this project using EasyEDA. The layout accommodates all components neatly and includes:

Wide tracks for power lines

• Wide tracks for power lines

Proper diode orientation for protection

• Proper diode orientation for protection

Clear labeling for connectors (Battery, Load, DC Input)

• Clear labeling for connectors (Battery, Load, DC Input)

Heat sink space for LM317 if needed

• Heat sink space for LM317 if needed

You can use this file with PCB manufacturers like JLCPCB, PCBWay, or EasyEDA to fabricate your board.

⚙️ How It Works

1. Charging Mode

The DC power input feeds the LM317 regulator.

• The DC power input feeds the LM317 regulator.

Voltage is adjusted via RP1 to safely charge a 12V lead-acid battery (typically 13.6V to 13.8V).

• Voltage is adjusted via RP1 to safely charge a 12V lead-acid battery (typically 13.6V to 13.8V).

LED1 lights up when charging is active.

• LED1 lights up when charging is active.

2. Automatic Load Switching

When the battery voltage is healthy, the relay activates and powers the load.

• When the battery voltage is healthy, the relay activates and powers the load.

If voltage drops below the set threshold, the relay disconnects the load to protect the battery.

• If voltage drops below the set threshold, the relay disconnects the load to protect the battery.

LED2 shows load status.

• LED2 shows load status.

3. Protection Circuit

Diodes D5, D6, and D3 protect against reverse polarity and relay back-EMF.

• Diodes D5, D6, and D3 protect against reverse polarity and relay back-EMF.

🔋 Applications

Emergency 12V Lighting

• Emergency 12V Lighting

DIY Mini UPS

• DIY Mini UPS

Battery Maintenance Station

• Battery Maintenance Station

Solar Power Backup System

• Solar Power Backup System

🛠️ Tips for Builders

Use a heatsink on LM317 if drawing more than 1A.

• Use a heatsink on LM317 if drawing more than 1A.

Test voltage levels before connecting a battery.

• Test voltage levels before connecting a battery.

Enclose the PCB in a plastic casing for safety.

• Enclose the PCB in a plastic casing for safety.

📹 Optional: Video Tutorial

If you're looking for a step-by-step build video, subscribe to our YouTube channel for Bangla DIY electronics tutorials!

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📌 Conclusion

With this simple yet effective DIY Mini IPS system, you can build your own automatic 12V load switch and charger. It's a great beginner project to learn about power electronics, voltage regulation, and PCB design.

Let me know if you make one yourself — I’d love to see it!