This is the Python code for Cheap UPS solution for Raspberry Pi 4b tutorial from Instructables.

It uses an "3A Fast Charge UPS Power Supply module" to provide a cheap power backup solution for Raspberry Pi 4. The INA226 module provides voltage, current and power monitor and is connected by the I2C bus.

To interface with the ina226 module the script uses the pi_ina226 library.

Install and usage:

Install the pigpio library, enable and start it:

sudo apt-get install pigpio
sudo systemctl enable pigpiod
sudo systemctl start pigpiod

Clone or download this repo:

cd pi4UPS/

pip3 install -r requirements.txt

There are two ways of running the UPS script:

1. runnning in terminal:

Edit the powerUPS.py file and set the following:

the sense pin from the battery, the resistor divider output is Low at power loss.

PowerSense_GPIO = 4

set to False if you don't need scheduled readings.

heartBeat = True

Change the value based on the shunt resistor installed on your INA266 module.

shunt = 0.008 ### the shunt resistance in Ohms

python3 powerUPS.py

The script is active, monitoring pin 4 for a power loss event.

Press Ctrl+C to exit the script and stop the monitoring.

Script running in terminal

2. Install as a service on Ubuntu with Systemd:

Edit the pi4ups.service file:

• set your actual username after User=
• set the WorkingDirectory= containing the ups_daemon.py file
• set the proper path to your script in ExecStart=

Edit the ups_daemon.py file, set PowerSense_GPIO and shunt values.

$ sudo cp pi4ups.service /etc/systemd/system/

$ sudo systemctl start pi4ups.service

$ sudo systemctl enable pi4ups.service

Check if the service is running without errors:

$ sudo systemctl status pi4ups.service

Testing

The script has been tested on the Raspi 4b+ on Ubuntu 22.04.4 aarch64 and Python 3.10, powerUPS.py is meant to be used from terminal and ups_daemon.py as a service. Check events.log for status/errors of the UPS service.