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4.1.8 Overheat Monitor

Introduction

You may want to make an overheat monitoring device that applies to various situations, ex., in the factory, if we want to have an alarm and the timely automatic turning off of the machine when there is a circuit overheating. In this project, we will use thermistor, joystick, buzzer, LED and LCD to make an smart temperature monitoring device whose threshold is adjustable.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Raphael Kit	337	Raphael Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION	PURCHASE LINK
GPIO Extension Board	BUY
Breadboard	BUY
Jumper Wires	BUY
Resistor	BUY
LED	BUY
Joystick Module	-
ADC0834	-
Transistor	BUY
I2C LCD1602	BUY
Thermistor	BUY
Buzzer	-

Schematic Diagram

T-Board Name	physical	wiringPi	BCM
GPIO17	Pin 11	0	17
GPIO18	Pin 12	1	18
GPIO27	Pin 13	2	27
GPIO22	Pin15	3	22
GPIO23	Pin16	4	23
GPIO24	Pin18	5	24
SDA1	Pin 3
SCL1	Pin 5

Experimental Procedures

Step 1: Build the circuit.

Step 2: Go to the folder of the code.

cd ~/raphael-kit/python-pi5

Step 3: Run the executable file.

sudo python3 4.1.13_OverheatMonitor_zero.py

As the code runs, the current temperature and the high-temperature threshold 40 are displayed on I2C LCD1602. If the current temperature is larger than the threshold, the buzzer and LED are started to alarm you.

Joystick here is for your pressing to adjust the high-temperature threshold. Toggling the Joystick in the direction of X-axis and Y-axis can adjust (turn up or down) the current high-temperature threshold. Press the Joystick once again to reset the threshold to initial value.

Note

• If you get the error FileNotFoundError: [Errno 2] No such file or directory: '/dev/i2c-1', you need to refer to I2C Configuration to enable the I2C.

• If you get ModuleNotFoundError: No module named 'smbus2' error, please run sudo pip3 install smbus2.

• If the error OSError: [Errno 121] Remote I/O error appears, it means the module is miswired or the module is broken.

• If the code and wiring are fine, but the LCD still does not display content, you can turn the potentiometer on the back to increase the contrast.

Code

Note

You can Modify/Reset/Copy/Run/Stop the code below. But before that, you need to go to source code path like raphael-kit/python. After modifying the code, you can run it directly to see the effect.

#!/usr/bin/env python3

import LCD1602
from gpiozero import LED, Buzzer, Button
import ADC0834
import time
import math

# Initialize joystick button, buzzer, and LED
Joy_BtnPin = Button(22)
buzzPin = Buzzer(23)
ledPin = LED(24)

# Set initial upper temperature threshold
upperTem = 40

# Setup ADC and LCD modules
ADC0834.setup()
LCD1602.init(0x27, 1)

def get_joystick_value():
    """
    Reads the joystick values and returns a change value based on the joystick's position.
    """
    x_val = ADC0834.getResult(1)
    y_val = ADC0834.getResult(2)
    if x_val > 200:
        return 1
    elif x_val < 50:
        return -1
    elif y_val > 200:
        return -10
    elif y_val < 50:
        return 10
    else:
        return 0

def upper_tem_setting():
    """
    Adjusts and displays the upper temperature threshold on the LCD.
    """
    global upperTem
    LCD1602.write(0, 0, 'Upper Adjust: ')
    change = int(get_joystick_value())
    upperTem += change
    strUpperTem = str(upperTem)
    LCD1602.write(0, 1, strUpperTem)
    LCD1602.write(len(strUpperTem), 1, '              ')
    time.sleep(0.1)

def temperature():
    """
    Reads the current temperature from the sensor and returns it in Celsius.
    """
    analogVal = ADC0834.getResult()
    Vr = 5 * float(analogVal) / 255
    Rt = 10000 * Vr / (5 - Vr)
    temp = 1 / (((math.log(Rt / 10000)) / 3950) + (1 / (273.15 + 25)))
    Cel = temp - 273.15
    return round(Cel, 2)

def monitoring_temp():
    """
    Monitors and displays the current temperature and upper temperature threshold.
    Activates buzzer and LED if the temperature exceeds the upper limit.
    """
    global upperTem
    Cel = temperature()
    LCD1602.write(0, 0, 'Temp: ')
    LCD1602.write(0, 1, 'Upper: ')
    LCD1602.write(6, 0, str(Cel))
    LCD1602.write(7, 1, str(upperTem))
    time.sleep(0.1)
    if Cel >= upperTem:
        buzzPin.on()
        ledPin.on()
    else:
        buzzPin.off()
        ledPin.off()

# Main execution loop
try:
    lastState = 1
    stage = 0
    while True:
        currentState = Joy_BtnPin.value
        # Toggle between settings and monitoring mode
        if currentState == 1 and lastState == 0:
            stage = (stage + 1) % 2
            time.sleep(0.1)
            LCD1602.clear()
        lastState = currentState
        if stage == 1:
            upper_tem_setting()
        else:
            monitoring_temp()
except KeyboardInterrupt:
    # Clean up and exit
    LCD1602.clear()
    ADC0834.destroy()

Code Explanation

1. This section imports necessary libraries for the project. LCD1602 is for the LCD display, gpiozero provides classes for LED, Buzzer, and Button, ADC0834 is for analog-to-digital conversion, and time and math are Python standard libraries for time-related functions and mathematical operations, respectively.

   #!/usr/bin/env python3
   
   import LCD1602
   from gpiozero import LED, Buzzer, Button
   import ADC0834
   import time
   import math
   

2. Here, the joystick button, buzzer, and LED are initialized. Button(22) creates a button object connected to GPIO pin 22. Buzzer(23) and LED(24) initialize the buzzer and LED to GPIO pins 23 and 24, respectively.

   # Initialize joystick button, buzzer, and LED
   Joy_BtnPin = Button(22)
   buzzPin = Buzzer(23)
   ledPin = LED(24)
   

3. Sets the initial upper temperature limit and initializes the ADC and LCD modules. The LCD is initialized with an address (0x27) and a mode (1).

   # Set initial upper temperature threshold
   upperTem = 40
   
   # Setup ADC and LCD modules
   ADC0834.setup()
   LCD1602.init(0x27, 1)
   

4. This function reads the joystick’s X and Y values using ADC0834. It returns a change value based on the joystick’s position, which will be used to adjust the temperature threshold.

   def get_joystick_value():
       """
       Reads the joystick values and returns a change value based on the joystick's position.
       """
       x_val = ADC0834.getResult(1)
       y_val = ADC0834.getResult(2)
       if x_val > 200:
           return 1
       elif x_val < 50:
           return -1
       elif y_val > 200:
           return -10
       elif y_val < 50:
           return 10
       else:
           return 0
   

5. Adjusts the upper temperature limit using the joystick input. The new limit is displayed on the LCD.

   def upper_tem_setting():
       """
       Adjusts and displays the upper temperature threshold on the LCD.
       """
       global upperTem
       LCD1602.write(0, 0, 'Upper Adjust: ')
       change = int(get_joystick_value())
       upperTem += change
       strUpperTem = str(upperTem)
       LCD1602.write(0, 1, strUpperTem)
       LCD1602.write(len(strUpperTem), 1, '              ')
       time.sleep(0.1)
   

6. Reads the current temperature from the sensor using ADC0834 and converts it to Celsius.

   def temperature():
       """
       Reads the current temperature from the sensor and returns it in Celsius.
       """
       analogVal = ADC0834.getResult()
       Vr = 5 * float(analogVal) / 255
       Rt = 10000 * Vr / (5 - Vr)
       temp = 1 / (((math.log(Rt / 10000)) / 3950) + (1 / (273.15 + 25)))
       Cel = temp - 273.15
       return round(Cel, 2)
   

7. Monitors and displays the current temperature and upper limit. If the temperature exceeds the upper limit, the buzzer and LED are activated.

   def monitoring_temp():
       """
       Monitors and displays the current temperature and upper temperature threshold.
       Activates buzzer and LED if the temperature exceeds the upper limit.
       """
       global upperTem
       Cel = temperature()
       LCD1602.write(0, 0, 'Temp: ')
       LCD1602.write(0, 1, 'Upper: ')
       LCD1602.write(6, 0, str(Cel))
       LCD1602.write(7, 1, str(upperTem))
       time.sleep(0.1)
       if Cel >= upperTem:
           buzzPin.on()
           ledPin.on()
       else:
           buzzPin.off()
           ledPin.off()
   

8. The main execution loop toggles between setting and monitoring modes based on joystick button presses. It continuously updates either the temperature setting or monitors the current temperature.

   # Main execution loop
   try:
       lastState = 1
       stage = 0
       while True:
           currentState = Joy_BtnPin.value
           # Toggle between settings and monitoring mode
           if currentState == 1 and lastState == 0:
               stage = (stage + 1) % 2
               time.sleep(0.1)
               LCD1602.clear()
           lastState = currentState
           if stage == 1:
               upper_tem_setting()
           else:
               monitoring_temp()
   

9. This section ensures proper cleanup and resource release when the program is interrupted.

   except KeyboardInterrupt:
       # Clean up and exit
       LCD1602.clear()
       ADC0834.destroy()