Voltage, current, temperature and date/time monitor using Arduino pro mini (ATmega328P). Data is recorded every specific range of time (this case every 30s), saved to a microSD card and shown in a 16x2 LCD display.
This code writes the data read in a microSD memory through SPI communication and MicroSD Adapter that includes a level shifter. The information is recorded in a CSV file format (Comma Separated Values) and then processed on the computer. Headers have to be created, in all memory files used, before running the system. The program uses two files:
1. DATA.txt: in this file all main values are saved in the following format:
Date, Time, Battery[V], Shunt_Bat[mV], Current[A], Temperature[°C]
Where Shunt_Bat[mV] is the shunt resistor voltage and Current[A] the current taken from the battery.
2. LOG.txt: this file is used to record every time the system is reset. This data is format as follows:
Date, Time, Log
Where Log is the log message, in this case it'll be "Reset System".
Data was analyzed by both Excel and Python code. For the second one, an script was created to export an XY chart in an SVG file. For that, all data in DATA.txt is converted to a CSV file and separed in two parts (whit the same headers or columns of DATA.txt file):
1. The first one, for all data which points to the discharge stage; this is named as 1_Discharge.csv. Then, the program reads the value in the Bateria[mV] columns for each row and creates an XY chart. Finally it's exported as an SVG file named 1_Discharge.svg.
2. The second part corresponds to the charge stage. Again, all the rows in data that refers to this stage are taken and saved in another CSV file named 2_Charge.csv. Then the scripts reads all values for both columns: Bateria[mV]and Current[A]. Finally an XY chart with double Y axis is created and exported as an SVG file and named 2_Charge.svg.
| Component | Reference |
|---|---|
| LCD Display | LCD 16x2 |
| I2C Converter | PCF8574 |
| Real Timer Clock | RTC - DS3231 |
| Analog/Digital Converter |
ADC ADS1115 |
| Pro mini Arduino Board |
Pro mini 328 5V/16MHz |
| MicroSD Module | MicroSD R/W |
The following image shows how the data is displayed in a 16x2 LCD.
The system was used to monitor an 12V uninterrupted power supply (UPS) charge and discharge cycles. A total of 2426 data where taken. The system was executed for around 20 hours and data were recorded every 30s. Then, the DATA.txt file is proccessed with Excel, python script (plot_script.py)and the following graphics were created.
DISCHARGING CYCLE: The discharge average current was around 1.25A.
CHARGING CYCLE: Battery is charge at 500mA. The orange curve shows the current behavior and the blue one the voltage behavior.
