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4.1.10 Overheat Monitor(MCP3008)

Note

Depending on your kit version, please identify whether you have ADC0834 or MCP3008 and proceed with the matching section.

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	-
MCP3008	-
Transistor	BUY
I2C LCD1602	BUY
Thermistor	BUY
Buzzer	-

Schematic Diagram

T-Board Name	physical	wiringPi	BCM
SPICE0	Pin 24	10	8
SPIMOSI	Pin 19	12	10
SPIMISO	Pin 21	13	9
SPISCLK	Pin 23	14	11
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: Set up the SPI interface and install the spidev library (see SPI Configuration for detailed instructions). If you have already completed these steps, you can skip this.

Step 3: Go to the folder of the code.

cd ~/raphael-kit/python

Step 4: Run the executable file.

sudo python3 4.1.13-2_OverheatMonitor.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 apt install python3-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.

Warning

If there is an error prompt RuntimeError: Cannot determine SOC peripheral base address, please refer to If gpiozero doesn’t work.

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 RPi.GPIO as GPIO
import spidev
import time
import math
import LCD1602

# GPIO pin definitions
JOY_BTN_PIN = 22  # Button pin
BUZZER_PIN = 23   # Buzzer pin
LED_PIN = 24      # LED pin

# Initialize GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setup(JOY_BTN_PIN, GPIO.IN, pull_up_down=GPIO.PUD_UP)
GPIO.setup(BUZZER_PIN, GPIO.OUT)
GPIO.setup(LED_PIN, GPIO.OUT)

# Set initial upper temperature threshold
upperTem = 40

# Initialize SPI for MCP3008
spi = spidev.SpiDev()
spi.open(0, 0)
spi.max_speed_hz = 1000000  # 1 MHz

# Initialize LCD1602
LCD1602.init(0x27, 1)

def read_adc(channel):
    """
    Read analog value from MCP3008 (0–7)
    """
    if channel < 0 or channel > 7:
        return -1
    adc = spi.xfer2([1, (8 + channel) << 4, 0])
    value = ((adc[1] & 0x03) << 8) | adc[2]
    return value

def get_joystick_value():
    """
    Reads the joystick values and returns a change value based on the joystick's position.
    """
    x_val = read_adc(1)
    y_val = read_adc(2)
    if x_val > 800:
        return 1
    elif x_val < 200:
        return -1
    elif y_val > 800:
        return -10
    elif y_val < 200:
        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 = read_adc(0)
    Vr = 3.3 * analogVal / 1023.0
    if Vr == 0:
        return 0
    Rt = 10000.0 * (3.3 - Vr) / Vr
    tempK = 1.0 / (((math.log(Rt / 10000.0)) / 3950.0) + (1.0 / (273.15 + 25.0)))
    Cel = tempK - 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:
        GPIO.output(BUZZER_PIN, GPIO.HIGH)
        GPIO.output(LED_PIN, GPIO.HIGH)
    else:
        GPIO.output(BUZZER_PIN, GPIO.LOW)
        GPIO.output(LED_PIN, GPIO.LOW)

# Main loop
try:
    lastState = GPIO.input(JOY_BTN_PIN)
    stage = 0
    while True:
        currentState = GPIO.input(JOY_BTN_PIN)
        if currentState == GPIO.HIGH and lastState == GPIO.LOW:
            stage = (stage + 1) % 2
            time.sleep(0.1)
            LCD1602.clear()
        lastState = currentState

        if stage == 1:
            upper_tem_setting()
        else:
            monitoring_temp()

except KeyboardInterrupt:
    pass

finally:
    LCD1602.clear()
    GPIO.cleanup()
    spi.close()

Code Explanation

1. Import Libraries

   This section loads the required libraries for GPIO, SPI, LCD display, time delays, and math operations.

   #!/usr/bin/env python3
   import RPi.GPIO as GPIO
   import spidev
   import time
   import math
   import LCD1602
   

2. GPIO and Device Setup

   Define GPIO pin numbers for the joystick button, buzzer, and LED, and configure GPIO modes.

   JOY_BTN_PIN = 22  # Button pin
   BUZZER_PIN = 23   # Buzzer pin
   LED_PIN = 24      # LED pin
   
   GPIO.setmode(GPIO.BCM)
   GPIO.setup(JOY_BTN_PIN, GPIO.IN, pull_up_down=GPIO.PUD_UP)
   GPIO.setup(BUZZER_PIN, GPIO.OUT)
   GPIO.setup(LED_PIN, GPIO.OUT)
   

3. SPI and LCD Initialization

   Start the SPI interface for MCP3008 and initialize the LCD1602 screen with I2C address 0x27.

   upperTem = 40
   spi = spidev.SpiDev()
   spi.open(0, 0)
   spi.max_speed_hz = 1000000
   
   LCD1602.init(0x27, 1)
   

4. Read ADC Value

   Reads analog data from MCP3008 ADC via SPI. Channel should be in range 0–7.

   def read_adc(channel):
       if channel < 0 or channel > 7:
           return -1
       adc = spi.xfer2([1, (8 + channel) << 4, 0])
       value = ((adc[1] & 0x03) << 8) | adc[2]
       return value
   

5. Joystick Movement Detection

   Checks X/Y axis values from the joystick and returns how much to change the threshold.

   def get_joystick_value():
       x_val = read_adc(1)
       y_val = read_adc(2)
       if x_val > 800:
           return 1
       elif x_val < 200:
           return -1
       elif y_val > 800:
           return -10
       elif y_val < 200:
           return 10
       else:
           return 0
   

6. Adjust Upper Temperature Threshold

   Displays “Upper Adjust” on the LCD and adjusts the threshold using joystick input.

   def upper_tem_setting():
       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)
   

7. Temperature Calculation

   Converts analog sensor reading to voltage, resistance, and finally temperature (Celsius) using Steinhart–Hart approximation.

   def temperature():
       analogVal = read_adc(0)
       Vr = 3.3 * analogVal / 1023.0
       if Vr == 0:
           return 0
       Rt = 10000.0 * (3.3 - Vr) / Vr
       tempK = 1.0 / (((math.log(Rt / 10000.0)) / 3950.0) + (1.0 / (273.15 + 25.0)))
       Cel = tempK - 273.15
       return round(Cel, 2)
   

8. Temperature Monitoring

   Continuously checks and displays temperature and upper limit. Turns on buzzer and LED if temperature exceeds the threshold.

   def monitoring_temp():
       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:
           GPIO.output(BUZZER_PIN, GPIO.HIGH)
           GPIO.output(LED_PIN, GPIO.HIGH)
       else:
           GPIO.output(BUZZER_PIN, GPIO.LOW)
           GPIO.output(LED_PIN, GPIO.LOW)
   

9. Main Program Logic

   Toggles between temperature monitoring and threshold setting modes when the joystick button is pressed.

   try:
       lastState = GPIO.input(JOY_BTN_PIN)
       stage = 0
       while True:
           currentState = GPIO.input(JOY_BTN_PIN)
           if currentState == GPIO.HIGH and lastState == GPIO.LOW:
               stage = (stage + 1) % 2
               time.sleep(0.1)
               LCD1602.clear()
           lastState = currentState
   
           if stage == 1:
               upper_tem_setting()
           else:
               monitoring_temp()
   

10. Cleanup on Exit

    Ensures proper shutdown of GPIO and SPI resources when Ctrl+C is pressed.

    except KeyboardInterrupt:
        pass
    finally:
        LCD1602.clear()
        GPIO.cleanup()
        spi.close()