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4.1.7 Smart Fan(MCP3008)

Note

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

Introduction

In this project, we will use motors, buttons and thermistors to make a manual + automatic smart fan whose wind speed 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
Power Supply Module	-
Thermistor	BUY
L293D	-
MCP3008	-
Button	BUY
DC Motor	BUY

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	Pin 15	3	22
GPIO5	Pin 29	21	5
GPIO6	Pin 31	22	6
GPIO13	Pin 33	23	13

Experimental Procedures

Step 1: Build the circuit.

Note

The power module can apply a 9V battery with the 9V Battery Buckle in the kit.

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: Get into the folder of the code.

cd ~/raphael-kit/python-pi5

Step 4: Run.

sudo python3 4.1.10-2_SmartFan_zero.py

As the code runs, start the fan by pressing the button. Every time you press, 1 speed grade is adjusted up or down. There are 5 kinds of speed grades: 0~4. When set to the 4^th speed grade and you press the button, the fan stops working with a 0 wind speed.

Once the temperature goes up or down for more than 2℃, the speed automatically gets 1-grade faster or slower.

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-pi5. After modifying the code, you can run it directly to see the effect.

#!/usr/bin/env python3

from gpiozero import Motor, Button
from time import sleep
import spidev
import math

# Initialize SPI for MCP3008
spi = spidev.SpiDev()
spi.open(0, 0)  # Bus 0, CE0 (GPIO8 / physical pin 24)
spi.max_speed_hz = 1000000  # 1 MHz

# Initialize GPIO pins for the button and motor control
BtnPin = Button(22)  # GPIO22 (physical pin 15)
motor = Motor(forward=5, backward=6, enable=13)  # GPIO5, GPIO6, GPIO13

# Initialize variables to track the motor speed level and temperatures
level = 0
currentTemp = 0
markTemp = 0

def read_adc(channel):
    """
    Reads analog value from MCP3008 channel (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 temperature():
    """
    Reads and calculates the current temperature from the sensor.
    Returns:
        float: The current temperature in Celsius.
    """
    analogVal = read_adc(0)  # Assuming thermistor connected to CH0
    Vr = 3.3 * analogVal / 1023.0  # For 3.3V system
    Rt = 10000.0 * Vr / (3.3 - Vr)
    temp = 1 / (((math.log(Rt / 10000.0)) / 3950.0) + (1 / (273.15 + 25.0)))
    Cel = temp - 273.15
    return Cel

def motor_run(level):
    """
    Adjusts the motor speed based on the specified level.
    Args:
        level (int): Desired motor speed level.
    Returns:
        int: Adjusted motor speed level.
    """
    if level == 0:
        motor.stop()
        return 0
    if level >= 4:
        level = 4
    motor.forward(speed=float(level / 4))
    return level

def changeLevel():
    """
    Changes the motor speed level when the button is pressed and updates the reference temperature.
    """
    global level, currentTemp, markTemp
    print("Button pressed")
    level = (level + 1) % 5
    markTemp = currentTemp

# Bind the button press event to changeLevel function
BtnPin.when_pressed = changeLevel

def main():
    """
    Main function to continuously monitor and respond to temperature changes.
    """
    global level, currentTemp, markTemp
    markTemp = temperature()
    while True:
        currentTemp = temperature()
        if level != 0:
            if currentTemp - markTemp <= -2:
                level -= 1
                markTemp = currentTemp
            elif currentTemp - markTemp >= 2:
                if level < 4:
                    level += 1
                markTemp = currentTemp
        level = motor_run(level)
        sleep(0.2)

# Run the main function and handle KeyboardInterrupt
try:
    main()
except KeyboardInterrupt:
    motor.stop()
    spi.close()

Code Explanation

1. Imports libraries for motor and button control, SPI communication with MCP3008, and mathematical computations. The gpiozer library is used for controlling GPIO devices, spidev for SPI communication with the MCP3008 ADC, and math for computing the temperature from resistance.

   #!/usr/bin/env python3
   
   from gpiozero import Motor, Button
   from time import sleep
   import spidev
   import math
   

2. Initializes SPI communication on bus 0, device 0 (CE0), which connects to the MCP3008 ADC chip.

   # Initialize SPI for MCP3008
   spi = spidev.SpiDev()
   spi.open(0, 0)  # Bus 0, CE0 (GPIO8 / physical pin 24)
   spi.max_speed_hz = 1000000  # 1 MHz
   

3. Sets up GPIO pin 22 as a button input, and configures the motor with GPIO pins 5 (forward), 6 (backward), and 13 (enable). Also declares global variables for motor speed level and temperature tracking.

   # Initialize GPIO pins for the button and motor control
   BtnPin = Button(22)  # GPIO22 (physical pin 15)
   motor = Motor(forward=5, backward=6, enable=13)  # GPIO5, GPIO6, GPIO13
   
   # Initialize variables to track the motor speed level and temperatures
   level = 0
   currentTemp = 0
   markTemp = 0
   

4. Defines a function to read analog values from the MCP3008 on a specified channel using SPI. The value returned is a 10-bit number (0–1023).

   def read_adc(channel):
       """
       Reads analog value from MCP3008 channel (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
   

5. Defines a function to read the temperature from the thermistor connected to MCP3008 channel 0. It converts the ADC value into voltage, calculates resistance, and then converts that into temperature in Celsius using the Steinhart-Hart approximation.

   def temperature():
       """
       Reads and calculates the current temperature from the sensor.
       Returns:
           float: The current temperature in Celsius.
       """
       analogVal = read_adc(0)  # Assuming thermistor connected to CH0
       Vr = 3.3 * analogVal / 1023.0  # For 3.3V system
       Rt = 10000.0 * Vr / (3.3 - Vr)
       temp = 1 / (((math.log(Rt / 10000.0)) / 3950.0) + (1 / (273.15 + 25.0)))
       Cel = temp - 273.15
       return Cel
   

6. A function to control motor speed based on the level (0–4). The motor stops at level 0, and for levels 1–4, the PWM speed is set proportionally (e.g., level 2 means 50% speed).

   def motor_run(level):
       """
       Adjusts the motor speed based on the specified level.
       Args:
           level (int): Desired motor speed level.
       Returns:
           int: Adjusted motor speed level.
       """
       if level == 0:
           motor.stop()
           return 0
       if level >= 4:
           level = 4
       motor.forward(speed=float(level / 4))
       return level
   

7. Defines a button event handler that increments the motor speed level from 0 to 4 in a cycle. It also updates the reference temperature when the level changes.

   def changeLevel():
       """
       Changes the motor speed level when the button is pressed and updates the reference temperature.
       """
       global level, currentTemp, markTemp
       print("Button pressed")
       level = (level + 1) % 5
       markTemp = currentTemp
   
   # Bind the button press event to changeLevel function
   BtnPin.when_pressed = changeLevel
   

8. The main logic continuously reads temperature and compares it with a reference value (markTemp). If the temperature difference is ±2°C, the motor speed level is adjusted accordingly. The motor is updated in each cycle, and a short delay avoids rapid switching.

   def main():
       """
       Main function to continuously monitor and respond to temperature changes.
       """
       global level, currentTemp, markTemp
       markTemp = temperature()
       while True:
           currentTemp = temperature()
           if level != 0:
               if currentTemp - markTemp <= -2:
                   level -= 1
                   markTemp = currentTemp
               elif currentTemp - markTemp >= 2:
                   if level < 4:
                       level += 1
                   markTemp = currentTemp
           level = motor_run(level)
           sleep(0.2)
   

9. Runs the main function inside a try-except block and ensures that the motor is stopped and SPI connection is closed gracefully if interrupted via Ctrl+C.

   # Run the main function and handle KeyboardInterrupt
   try:
       main()
   except KeyboardInterrupt:
       motor.stop()
       spi.close()