Off-grid Solar PV Panel project

Arduino IDE Installation and Configuration on a Raspberry Pi

Arduino LED Blink Program

• Program lights up Arduino UNO on-board LED connected to pin 13 for 1 second.

/*
  Blink

  Turns an LED on for one second, then off for one second, repeatedly.

*/

// the setup function runs once when you press reset or power the board

void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(13, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(13, HIGH);   // turn the LED on (HIGH is the voltage level) = 1 = 5V supply
  delay(1000);                       // wait for 1 second
  digitalWrite(13, LOW);    // turn the LED off by making the voltage LOW = 0 = 0V supply
  delay(1000);                       // wait for 1 second
}

Arduino UNO - Safety

• Wear eye protection.
• Always get a teacher to inspect your circuit before powering up.
• Wear cotton shirts and pants and closed shoes.
• Even low voltages can cause burns because wires can heat up if shorted.

Arduino UNO - Building a LED Blink Circuit on a Breadboard

• Build an external LED Blink Circuit for the Arduino UNO.

Arduino UNO - Building a Mini-Solar PV Circuit

• Demonstration on how to build a small PV circuit that charges a battery on an Arduino UNO.
• The circuit incorporates a Voltage Divider circuit.
• Click on Image below to download and watch video.

Raspberry Pi - Python Introductory Lesson

• Install software to help program in Python
• Explore some simple python coding and learn about indentation to delineate code blocks

Raspberry Pi and Arduino Serial Communication

• Write code for the Arduino UNO to send data to the Raspberry pi using Serial communication.
• Write code in Python on the Raspberry Pi to receive data from the Arduino UNO using Serial communication.
• Raspberry Pi requires the installation of:
  • sudo apt install python3-pip - pip to install python packages
  • python3 -m pip install pyserial - pySerial Library

Python code for Raspberry Pi to receive serial communication from the Arduino UNO

import serial

if __name__ == '__main__':
    ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)
    ser.reset_input_buffer()
    
    while True:
        if ser.in_waiting > 0:
            line = ser.readline().decode('utf-8').rstrip()
            print(line)

Arduino UNO - Reading the Voltage of the Small Solar PV Panel

• Learn how to read voltage readings from a small Solar PV panel connected to an Arduino UNO using a voltage divider circuit and analog pin A2.

Python - code to read data from solar panel each minute

Python - collecting data from the arduino

#!/usr/bin/env python3
import serial


if __name__ == '__main__':
    ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)
    ser.reset_input_buffer()

    while True:
        if ser.in_waiting > 0:
            line = ser.readline().decode('utf-8').rstrip()
            print(line)

Python - adding a datestamp

#!/usr/bin/env python3
import serial
import datetime


if __name__ == '__main__':
    ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)
    ser.reset_input_buffer()

    while True:
        if ser.in_waiting > 0:
            line = ser.readline().decode('utf-8').rstrip()
            print(line)
            
            now = datetime.datetime.now()
            date_stamp = now.strftime("%Y-%b-%d %H:%M:%S")
            print(f'This python program was run at this time {date_stamp}')
            
            data = str(line) + "," + date_stamp + "\n"
            print(f'The data is =  {data}')

Python - saving data to a file

#!/usr/bin/env python3
import serial
import datetime

if __name__ == '__main__':
    ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)
    ser.reset_input_buffer()

    while True:
        if ser.in_waiting > 0:
            line = ser.readline().decode('utf-8').rstrip()
            print(line)
            
            now = datetime.datetime.now()
            date_stamp = now.strftime("%Y-%b-%d %H:%M:%S")
            print(f'This python program was run at this time {date_stamp}')
            
            data = str(line) + "," + date_stamp + "\n"
            print(f'The data is =  {data}')

            f = open('/home/pi/solar_project/solar_data.txt','a')
            f.write(data)
            f.close()

Python - with graphing in Plotly

#!/usr/bin/env python3
import serial
import datetime
import plotly
import plotly.graph_objects as go
import pandas

if __name__ == '__main__':
    ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)
    ser.reset_input_buffer()

    while True:
        if ser.in_waiting > 0:
            line = ser.readline().decode('utf-8').rstrip()
            print(line)
            
            now = datetime.datetime.now()
            date_stamp = now.strftime("%Y-%b-%d %H:%M:%S")
            print(f'This python program was run at this time {date_stamp}')
            
            data = str(line) + "," + date_stamp + "\n"
            print(f'The data is =  {data}')

            f = open('/home/pi/solar_project/solar_data.txt','a')
            f.write(data)
            f.close()
            
            # import and plot data text file
            df = pandas.read_csv('/home/pi/solar_project/solar_data.txt')

            fig = go.Figure(data = go.Scatter(mode='markers',
                                                x=df.date_time,
                                                y=df.solar_value,
                                                marker=dict(
                                                    color="LightSkyBlue",
                                                    size=20)
                                                )
                                        )
            fig.update_layout(title="Solar Panel Test",
                                xaxis_title = 'Time',
                                yaxis_title = 'Solar Panel Voltage',
                                font=dict(
                                    size=20,
                                    color="RebeccaPurple"
                                )
                            )

            plotly.offline.plot(fig,
                                filename="/home/pi/solar_project/solar_panel_graph.html",
                                auto_open=False)

            print("Solar Panel data plotted")

Python - Reading Solar PV Voltage using Python

• Learn how to:
  • Read solar PV voltage analog values in Python
  • Convert the solar PV values into voltage
  • Format the voltage values to three decimal points.

import serial

if __name__ == '__main__':
    ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)
    ser.reset_input_buffer()
    
    while True:
        if ser.in_waiting > 0:
            line = ser.readline().decode('utf-8').rstrip()
            try:
                voltage = int(line)
            except:
                voltage = 0
            voltage_corrected = voltage * (5.0 / 1023.0) * 2
            
            # https://thepythonguru.com/python-string-formatting/
            #  {0} - first formatted term. If there were more terms they would be shown as {1}, {2}, etc.
            #  .3  - three decimal points
            #   f  - floating point numbers = decimal numbers
            #   .format() - variables to format
            voltage_string = '{0:.3f}'.format(voltage_corrected)

Python - Saving Data in a Text File

import serial
# from datefime module import datetime class
from datetime import datetime

if __name__ == '__main__':
    ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)
    ser.reset_input_buffer()
    
    while True:
        if ser.in_waiting > 0:
            line = ser.readline().decode('utf-8').rstrip()
            try:
                voltage = int(line)
            except:
                voltage = 0
            voltage_corrected = voltage * (5.0 / 1023.0) * 2
            
            voltage_string = '{0:.3f}'.format(voltage_corrected)
            
            now = datetime.now()
            # The strftime method is used to create formatted Strings
            time_stamp = now.strftime("%Y-%b-%d %H:%M:%S")
            print(f'Current time is {time_stamp} and corrected voltage {voltage_string}')
            
            if now.strftime("%S") == "00":
                # save the data in a file every minute
                data = time_stamp + "," + voltage_string + "\n"
                f = open('/home/pi/Arduino/small_solar_arduino_data.txt','a')
                f.write(data)
                f.close()
                print("Data saved")

Python - Final code

• The final code displayed below accepts
  • two data values from the Arduino (voltage and fanOn)
  • add a datetime stamp
  • Dweets the data to the cloud
  • saves the data in a file namedsolar_arduino_data.txt
  • and plots the data using Plotly and saves the plot in a file names arduino_solar.html

#!/usr/bin/env python3
import serial
import requests
import datetime
import plotly
import plotly.graph_objects as go
import pandas
import time

if __name__ == '__main__':
    ser = serial.Serial('/dev/ttyUSB0', 9600, timeout=1)
    ser.reset_input_buffer()

    #cycle = 0
    #good_data = 0

    for i in range(5):
        voltage_string = ''
        now = datetime.datetime.now()
        date_stamp = now.strftime("%Y-%b-%d %H:%M:%S")
        
        if ser.in_waiting > 0:
            line = ser.readline().decode('utf-8').rstrip()
            print(f"separated using commas {line.split(',')}")
            mylist = line.split(',')
            try:
                voltage = int(mylist[0])
                print(voltage)
                fanOn = int(mylist[1])
            except:
                voltage = 0
                fanOn = 0
            voltage_correct = voltage * (5.0 / 1023.0) * 2
            print('The solar panel voltage = {0:.3f}'.format(voltage_correct))
            print(f'Fan status is {fanOn}')
            #print(f'The cycle is {cycle}')
            print(f'datestamp is {date_stamp}')
            voltage_string = '{0:.3f}'.format(voltage_correct)
            fanOn_string = str(fanOn)
            #cycle = cycle + 1
        time.sleep(1)
            
    print("Preparing dweet")
    dweet_dict = {}
    dweet_dict.update({"solar_voltage": voltage_string})
    dweet_dict.update({"fanOn": fanOn_string})
    dweet_dict.update({"date_stamp": date_stamp})
    url = "https://dweet.io/dweet/for/bundoora-*****************?"
    #x = requests.post(url, json=dweet_dict)
    #print(x.text)


    data = ""
    data = date_stamp + "," + voltage_string + "," + fanOn_string + '\n'
    f = open('/home/pi/Arduino/solar_arduino_data.txt','a')
    f.write(data)
    f.close()

    df = pandas.read_csv('/home/pi/Arduino/solar_arduino_data.txt')

    fig = go.Figure(data = go.Scatter(mode='markers',
                                        x=df.Date,
                                        y=df.Volt,
                                        marker=dict(
                                            color="LightSkyBlue",
                                            size=20)
                                        )
                    )
    fig.update_layout(title="Arduino Solar Voltage",
                        xaxis_title = 'Time',
                        yaxis_title = 'Voltage',
                        font=dict(
                            size=20,
                            color="RebeccaPurple"
                            )
                        )
    plotly.offline.plot(fig,
                        filename="/home/pi/Arduino/arduino_solar.html",
                        auto_open=False)
    print("Voltage plotted")