DIY Smart Home UPS 🔋⚡

A set of modular, low-cost, and smart Uninterruptible Power Supplies (UPS) designed to protect and monitor critical smart home devices like Mini PCs, Routers, ONTs, and IP Cameras.

(Left: Wi-Fi Monitored Version | Right: Standard Compact Version)

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🚀 Overview

This project provides a complete blueprint for building your own DC UPS units for approximately €10-15. Unlike standard commercial units, these are designed to be integrated into Home Assistant via MQTT, providing real-time telemetry of battery health and power grid status.

Key Features

• Low Cost: Built using standard components (€12 for WiFi version, €9 for basic).
• High Performance: Up to 24W (35W peak) output, perfect for Mini PCs (Intel N5095) and Routers.
• Smart Monitoring: Integrated ESP8266 (Wemos D1 Mini) running Tasmota.
• Seamless Transition: Zero-millisecond switching between grid and battery power.
• Autonomy: 1-2.5 hours of backup time depending on the load.
• Thermal Tested: Successfully validated with thermal imaging under 100% load.

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🛠️ Hardware Specifications

Main Controller: DC UPS V4.0CN (Red Board)

• Charger: CN3762 (CC/CV profile for 2S Li-ion).
• Protection (BMS): HY2120 + dual FS8205A MOSFETs.
• Booster: XR2682 (Step-up to 12V).
• Cells: 2x Samsung INR18650-35E (3400mAh, 8A discharge).

Monitoring Module (WiFi Version)

• MCU: Wemos D1 Mini (ESP8266).
• Power Supply: ME3116 Buck converter (12V to 5V).
• Sensors: Voltage dividers for Vin (Grid status) and Vbat (Analog mapping).

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📊 System Architecture

graph TD
    AC[230V AC Grid] ==> ADP[AC/DC Adapters]
    ADP ==> UPS[DIY UPS Units]
    UPS ==> DEV[Critical Devices]
    UPS -.->|WiFi MQTT| HA[Home Assistant]
    
    subgraph "Monitored Unit"
        UPS
    end

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⚙️ Software & Integration

Firmware: Tasmota

The monitoring module uses standard Tasmota with a custom template:

• Profile: Generic (18)
• ADC Calibration: Mapped to 0-9900mV (configurable).
• MQTT Rules: Immediate state pushing for Vin, Charging, and Done signals.

Home Assistant Integration

Includes a custom MQTT Sensor and a Template Sensor for real-time voltage calculation:

# Example Template Sensor
template:
  - sensor:
      - name: "UPS Battery Voltage"
        state: "{{ (states('sensor.ups_battery_voltage_raw') | float * 8.4 / 1023) | round(2) }}"
        unit_of_measurement: "V"
        device_class: voltage

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📂 Project Structure

• 📁 assets/: Project images, schematics, and thermal captures.
• 📁 annexes/: Component datasheets (Samsung, CN3762, XR2682, etc.) and Tasmota backup files.
• 📘 DIY UPS Project.md: Complete technical documentation in English.
• 📘 Proyecto UPS.md: Documentación técnica completa en Español.

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📸 Gallery

Internal Assembly Diagram

Thermal stress test pass (Visible vs Thermal)

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⚖️ License

This project is for educational and DIY purposes. Always handle Li-ion batteries with care.

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Developed for a robust and affordable Smart Home infrastructure.