Python user interface for Raspberry Pi driven automated load bank
An automated resistive load bank was created to test and optimize hydrogen fuel cells for the University of Alberta EcoCar team. The load bank utilizes a touchscreen graphical user interface to select automated testing cycles and pulse width modulation for a variable load. The load bank handles up to 60 A of current from the 46 V fuel cell with 1000 W of power dissipation capability. Furthermore, it is battery powered, portable, and weather resistant.
The automated load bank is managed primarily by a Raspberry Pi computer, and its I/O capabilities are extended using an Atmel ATMega328P. In this repository lies the software for the Raspberry Pi. The software is primarily written in Python and uses the TkInter graphics library to develop a touchscreen user interface.
Raspberry Pi to ATMega328P
- 0 -- Stop output
- 1-120 -- Desired load in steps. Step size is 0.5 A, so a value of 64 would correspond to a 32 A load.
- 121 -- Start an air starve cycle. Operating parameters are set in the ATMega328P.
- 122 -- Data request for all inputs read by ATMega328P. (Fuel cell voltage, fuel cell current, battery voltage)
- 123 -- Trigger to tell ATMega328P that fan speeds will be sent next.
- WARNING: Sending values greater than 123 will be interpreted by the ATMega328P as desired current values of greater than 60 A which is outside the design parameters for the hardware.
ATMega328P to Raspberry Pi
Install Raspbian operating system using Etcher to put the latest image on an SD card
TUTORIAL
Set date for Wi-Fi access
sudo date -s "Dec 27 14:54"
Update software repositories & installed software
TUTORIAL
sudo apt-get update
sudo apt-get dist-upgrade
Install "Matchbox" on-screen software keyboard
sudo apt-get install matchbox-keyboard
Install TkInter and Python image library
sudo apt-get install tk
sudo apt-get install python-imaging
sudo apt-get install python-imaging-tk
sudo apt-get install python3-pil.imagetk
Set Python3 as default environment
Edit bash file: nano ~/.bashrc
Add at the end:
alias python='/usr/bin/python3'
alias pip=pip3
Run bash file: source ~/.bashrc
Enable I2C
sudo raspi-config -> 5 Interfacing Options -> P5 I2C -> yes -> Finish
Set I2C Speed
REFERENCE
sudo nano /boot/config.txt
dtparam=i2c_arm=on,i2c_arm_baudrate=15000 (for 15kHz baud rate)
Add Matplotlib dependencies
sudo apt-get install libatlas3-base libffi-dev at-spi2-core python3-gi-cairo
pip install cairocffi
pip install matplotlib
Display brightness
sudo bash -c "echo n > /sys/class/backlight/rpi_backlight/brightness"
where 0 < n < 255 (255 is maximum brightness)
Alternate Method
>>> import rpi_backlight as bl
>>> bl.set_brightness(255)
>>> bl.set_brightness(20, smooth=True, duration=3)
>>> bl.get_max_brightness()
255
>>> bl.get_actual_brightness()
20
>>> bl.get_power()
True
>>> bl.set_power(False)