Fridge Smart Plug Power Controller

A Python microservice that automatically controls an outdoor fridge based on ambient temperature. It turns the fridge ON when it's warm enough to need cooling, and turns it OFF when it's too cold; protecting both the appliance and the food inside.

Fig. 1: Controller 0.3.0 system overview

The Problem

I keep a fridge on my terrace for weekly meal prep, but standard fridges aren't designed to operate in temperatures below $10 \degree \text{C}$. During winter, outdoor temperatures fluctuate: leaving the fridge off risks food spoilage when daytime temperatures rise above $10 \degree \text{C}$, while leaving it on in very cold conditions could damage the compressor and other components.

The Solution

This service connects to a Tapo smart plug (P110) and monitors outdoor temperature via either:

• Local Tapo T310 temperature sensor through Tapo H100 hub, or
• OpenWeatherMap API.

When the temperature rises above a safe threshold, it turns the fridge on. When it drops back below the threshold, it turns the fridge off. The fridge runs only when needed, reducing the risk of damage even though I’m operating it under suboptimal conditions (around $5 \degree \text{C}$).

How It Works

Description	Default Temperature	Action
Temperature above threshold	$≥5 \degree \text{C}$	Plug turns ON (fridge runs)
Temperature below threshold - delta	$≤3 \degree \text{C}$	Plug turns OFF (fridge stops)
Temperature in between (hysteresis window)	$3–5 \degree \text{C}$	Idle (no change, prevents rapid switching)

Note

A configurable hysteresis (TEMPERATURE_DELTA) avoids rapid on/off cycling when the temperature hovers near the threshold.

Installation

1. Clone the repository:

   git clone https://github.com/AleksaMCode/fridge-smart-plug-power-controller.gits
   cd fridge-smart-plug-power-controller

2. Create a virtual environment and install dependencies:

   python -m venv venv
   source venv/bin/activate
   pip install -r requirements.txt

3. Copy the settings template and configure:

   cp settings.template settings.py

   Edit settings.py with your credentials and preferences.

Usage

Run the controller:

python controller.py

Or use the provided script:

./start_controller.sh

The service runs continuously, checking temperature every $10$ minutes and adjusting the plug state accordingly. Logs are written to logs/fsppc-info.log and to the console.

Running on System Startup (Cron)

To run the controller automatically when the system boots, add a cron job using @reboot:

1. Make the script executable (if not already):

   chmod +x start_controller.sh

2. Open the crontab for the user that will run the controller:

   crontab -e

3. Add this line (replace /path/to/fridge-smart-plug-power-controller with your actual project path):

   @reboot cd /path/to/fridge-smart-plug-power-controller && ./start_controller.sh >> logs/cron.log 2>&1 &
   

   The controller must be started from the project directory so the virtual environment and settings.py are found. The trailing & runs it in the background so cron does not block. Output is appended to logs/cron.log for debugging.

Tip

The controller will start once at boot and keep running. If you prefer automatic restarts on failure, consider a systemd service or process manager like supervisord instead.