Python tutorials
Preparations for Python
Python is a programming language that lets you work more quickly and integrate your systems more effectively.
Python is an interpreted, high-level and general-purpose programming language. Python’s design philosophy emphasizes code readability with its notable use of significant whitespace. Its language constructs and object-oriented approach aim to help programmers write clear, logical code for small and large-scale projects.
Next to pick up Python to control 40 pin of Raspberry Pi.
Copy Example Code Folder to Raspberry Pi：
Place example code folder to the pi folder of Raspberry Pi. and extract the example code from pythonCode_A zip file, as shown below:
Double-click pythonCode_A folder to look through compiled files, as shown below:
Set the default editor of file with .py
Right-click“Open with…”
Click Programming to select Geany Programmer’s Editor
Then, we can directly open file by doubl-click Geany Programmer’s Editor
Print“Hello World”
One is to double-click 1_HelloWorld.py and tap 
to compile code and check grammar errors. After successful compilation, tap 
to run the code. At same time, terminal appears and prints “hello world”.
The other way is to open terminal directly, input the following commands and press“Enter”to print“hello world！”
cd pythonCode_A
python 1_HelloWorld.py
Detailed Projects
Note: G, - and GND marked on sensors and modules are so-called negative, which are connected to GND of GPIO extension board or “-” of breadboard; V、+、VCC are known as positive, which are interfaced 3V3 or 5V on extension board and“+”on breadboard.
Project 1：Python3 Shell
Use windows remote desktop connection to enter the page of Raspberry Pi, then open its terminal.
Input python3 in terminal and enter the python3 shell interface, then input print(“hello,world!”) and press“Enter”, “hello,world ! will be output.
You may find function print() is used to print data.
You could print other type data, like Mathematical formula:
print(1+5)
Variable a = 2 b = 5
print(a*b)
As shown below:
Input exit() to exit python3 shell
Project 2：LED Blink
Description：
Let’s start from a rather basic and simple experiment—-LED Blink
Components：
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|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Jumper Wires*1 |
Breadboard*1 |
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|
|
|
LED - Red *1 |
220Ω Resistor*1 |
Jumper Wires |
Component Description：
LED:
A light-emitting diode, the current is connected when anode(long pin) is connected to VCC, and cathode(short pin)is connected to GND. Its brightness is 2V and current is 6mA. LED must be connected to a resistor in the circuit, otherwise, the components will be burned.
Resistor:
We use a carbon film resistor, 220Ωand its accuracy is 5%, why choose 220Ω resistor?
Since the high-level output voltage of GPIO pin of the Raspberry Pi is 3.3V, and the voltage of the LED is about 2V, and the current is about 6mA, we need to use a resistor to bear the voltage (3.3V-2V) = 1.3V, according to ohm The law: U/I = R knows: (3.3-2)/6 * 1000 ≈ 217Ω.
Breadboard:
Below is a short instruction of breadboard. The holes on the board are connected. The inner board is structure diagram.
Schematic Diagram：
Connection Diagram
Since the PIN numbers of GPIO Extension Board and RPi GPIO are same, the part of breadboard and GPIO Extension Board is only shown on further connection diagram.
Working Principle：
The positive pole of LED is connected to GPIO18, when the pin of GPIO18 outputs 3.3V, LED will be on; when its pin outputs 0V, LED will be off.
Run Example Code
Input the following commands in the terminal and press“Enter”
cd /home/pi/pythonCode_A
python 2_Led_Blink.py
Test Result：
Terminal prints and LED flashes.
Note: Press Ctrl + C on keyboard and exit code running
Example Code：
import RPi.GPIO as GPIO
import time
ledPin = 18 ##define led pin
GPIO.setmode(GPIO.BCM) ## use BCM numbers
GPIO.setup(ledPin,GPIO.OUT) ##set the ledPin OUTPUT mode
GPIO.output(ledPin,GPIO.LOW) ## make ledPin output LOW level
while True: ##loop
GPIO.output(ledPin,GPIO.HIGH) ##turn on led
print("turned on the led") ##Print in the terminal
time.sleep(1) ##wait for 1 second
GPIO.output(ledPin,GPIO.LOW) ##turn off led
print("turned off the led")
time.sleep(1)
GPIO.cleanup() ##release all GPIO
Explanation：
While
While is the loop statement of python，when the condition is true, the program will be executed always be executed.
import RPi.GPIO as GPIO
Import RPi.GPIO library，which can be used to control the digital output of Raspberry Pi and PWM output.
GPIO.setmode(GPIO.BCM)
There are many definitions about pins of Raspberry Pi, on this condition, we definite pin as BCM digital pin.
More resource：
https://sourceforge.net/p/raspberry-gpio-python/wiki/Examples/
import time
Import time library, time.sleep(1) means waiting for a second, more resource：
https://sourceforge.net/p/raspberry-gpio-python/wiki/Examples/
Project 3：SOS Light
Description：
S.O.S is a Morse code distress signal , used internationally, that was originally established for maritime use. We will present it with flashing LED
Components:
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|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
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|
|
LED - Red *1 |
220ΩResistor*1 |
Jumper Wires |
Schematic Diagram：
Connection Diagram:
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 3_LED_SOS.py
Test Result：
LED flashes quickly for three times, three times slowly and quickly three times, the terminal prints … _ _ _ …
Note: Press Ctrl + C on keyboard and exit code running.
Example Code:
import RPi.GPIO as GPIO
import time
ledPin = 18 ##define led pin
i1 = 0
i2 = 0
i3 = 0
GPIO.setmode(GPIO.BCM) ## use BCM numbers
GPIO.setup(ledPin,GPIO.OUT) ##set the ledPin OUTPUT mode
GPIO.output(ledPin,GPIO.LOW) ## make ledPin output LOW level
while True: ##loop
while(i1<3):
GPIO.output(ledPin,GPIO.HIGH) ##turn on led
time.sleep(0.1) ##wait for 1 second
GPIO.output(ledPin,GPIO.LOW) ##turn off led
time.sleep(0.1)
print(".")
i1 += 1
while(i2<3):
GPIO.output(ledPin,GPIO.HIGH) ##turn on led
time.sleep(1) ##wait for 1 second
GPIO.output(ledPin,GPIO.LOW) ##turn off led
time.sleep(1)
print("_")
i2 += 1
while(i3<3):
GPIO.output(ledPin,GPIO.HIGH) ##turn on led
time.sleep(0.1) ##wait for 1 second
GPIO.output(ledPin,GPIO.LOW) ##turn off led
time.sleep(0.1)
print(".")
i3 += 1
time.sleep(3)
i1 = 0
i2 = 0
i3 = 0
GPIO.cleanup() ##release all GPIO
Project 4：Breathing LED
Description：
A“breathing LED”is a phenomenon where an LED’s brightness smoothly changes from dark to bright and back to dark, continuing to do so and giving the illusion of an LED“breathing.”This phenomenon is similar to a lung breathing in and out. So how to control LED’s brightness? We need to take advantage of PWM.
Components：
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|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
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|
LED - Red *1 |
220ΩResistor *1 |
Jumper Wires |
Working Principle：
We use the PWM output of GPIO, PWM outputs analog signals and output value is 0~100 which is equivalent to output voltage 0~3.3V from GPIO port.
According to Ohm’s law: U/R = I, the resistance is 220Ω, and the value of voltage U changes, so does the value of current I, which can control the brightness of the LED lamp.
PWM (Pulse Width Modulation) is the control of the analog circuit through the digital output of microcomputer and a method that making digital coding on analog signal levels
It sends square waves with certain frequency through digital pins, that is, high level and low level are output alternately for a period of time. Total time of each group high and low level is fixed, which is called cycle.
The time of high level output is pulse width whose percentage is called Duty Cycle. The longer that high level lasts, the larger the duty cycle of analog signals is, the corresponding voltage as well
Below chart is pulse width 50%, then the output voltage is 3.3 * 50% = 1.65V，the brightness of LED is medium.
Schematic Diagram：
Connection Diagram
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 4_Led_Breath.py
Test Result：
LED gradually brightens then darkens.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
import RPi.GPIO as GPIO
import time
ledPin = 18 ##define led pin
GPIO.setmode(GPIO.BCM) ## use BCM numbers
GPIO.setup(ledPin,GPIO.OUT) ##set the ledPin OUTPUT mode
GPIO.output(ledPin,GPIO.LOW) ## make ledPin output LOW level
pwm = GPIO.PWM(18,100) ##create a PWM instance
pwm.start(0) ##start PWM
def brighten(): ##define function
for i in range(0,100,+1):
pwm.ChangeDutyCycle(i) ##change the frequency,To lighten gradually
time.sleep(0.01)
def darken():
for i in range(100,0,-1):
pwm.ChangeDutyCycle(i) ##To darken gradually
time.sleep(0.01)
while True: ##loop
brighten() ##call function
darken()
pwm.stop() ##stop PWM
GPIO.cleanup() ##release all GPIO
Project 5：Traffic Lights
Description：
In this lesson, we will learn how to control multiple LED lights and simulate the operation of traffic lights.
Traffic lights are signalling devices positioned at road intersections, pedestrian crossings, and other locations to control flows of traffic.
Green light on: Allows traffic to proceed in the direction denoted, if it is safe to do so and there is room on the other side of the intersection.
Red light: Prohibits any traffic from proceeding. A flashing red indication requires traffic to stop and then proceed when safe (equivalent to a stop sign).
Amber light (also known as ‘orange light’ or ‘yellow light’):
Warns that the signal is about to change to red, with some jurisdictions requiring drivers to stop if it is safe to do so, and others allowing drivers to go through the intersection if safe to do so.
Components：
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|
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|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
|
|
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LED - Red *1 |
LED - Green*1 |
LED - Yellow*1 |
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|
Breadboard*1 |
220Ω Resistor*3 |
Jumper Wires |
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 5_traffic_light.py
Test Result：
Red light is on 5s and off, yellow light flashes 3s and turn off, green light is lit for 5s and off, in loop way.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
import RPi.GPIO as GPIO
from time import sleep
##LED pin
red = 18
yellow = 23
green = 24
GPIO.setmode(GPIO.BCM) ## use BCM numbers
GPIO.setup(red,GPIO.OUT) ##set the ledPin OUTPUT mode
GPIO.setup(yellow,GPIO.OUT)
GPIO.setup(green,GPIO.OUT)
GPIO.output(red,GPIO.LOW)
GPIO.output(yellow,GPIO.LOW)
GPIO.output(green,GPIO.LOW)
while True:
GPIO.output(red,GPIO.HIGH)
sleep(5)
GPIO.output(red,GPIO.LOW)
GPIO.output(yellow,GPIO.HIGH) ##turn on yellow_led
sleep(0.5)
GPIO.output(yellow,GPIO.LOW) ##turn off yellow_led
sleep(0.5)
GPIO.output(yellow,GPIO.HIGH)
sleep(0.5)
GPIO.output(yellow,GPIO.LOW)
sleep(0.5)
GPIO.output(yellow,GPIO.HIGH)
sleep(0.5)
GPIO.output(yellow,GPIO.LOW)
sleep(0.5)
GPIO.output(green,GPIO.HIGH) ##turn on green_led
sleep(5) ##delay 5s
GPIO.output(green,GPIO.LOW) ##turn off green_led
GPIO.cleanup() ##release all GPIO
Project 6：RGB Light
Description：
In this chapter, we will demonstrate how RGB lights show different colors via programming.
Components：
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|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
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|
RGB - LED *1 |
100Ω Resistor*3 |
Jumper Wires |
Component Knowledge：
We use common cathode RGB lights.
Working Principle：
RGB LED integrated three LEDs emitting red,green and blue light. It has 4 pins，long pin (-) is a shared pin, that is, the negative port of 3LED, as shown below, we control three LEDs to emit light with different brightness to make RGB show different colors.
Red, green and blue are three primary colors. They could produce all kinds of visible lights when mixing them up. Computer screen, single pixel mobile phone screen, neon light work under this principle.
Next, we will make a RGB LED displaying all kinds of colors.
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 6_RGB_led.py
Test Result：
RGB lights show colors randomly.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
import RPi.GPIO as GPIO
from time import sleep
import random
##define RGB pin
pin_R = 24
pin_G = 23
pin_B = 18
GPIO.setmode(GPIO.BCM) ## use BCM numbers
##set the RGB Pin OUTPUT mode
GPIO.setup(pin_R,GPIO.OUT)
GPIO.setup(pin_G,GPIO.OUT)
GPIO.setup(pin_B,GPIO.OUT)
## makeRGB Pin output LOW level
GPIO.output(pin_R,GPIO.HIGH)
GPIO.output(pin_G,GPIO.HIGH)
GPIO.output(pin_B,GPIO.HIGH)
##set pwm frequence to 1000hz
pwm_R = GPIO.PWM(pin_R,100)
pwm_G = GPIO.PWM(pin_G,100)
pwm_B = GPIO.PWM(pin_B,100)
##set inital duty cycle to 0
pwm_R.start(0)
pwm_G.start(0)
pwm_B.start(0)
##function. receive the value to display different colors
def setColor(val_R,val_G,val_B):
pwm_R.ChangeDutyCycle(val_R)
pwm_G.ChangeDutyCycle(val_G)
pwm_B.ChangeDutyCycle(val_B)
while True:
## get a random in 0~100
R = random.randint(0,100)
G = random.randint(0,100)
B = random.randint(0,100)
setColor(R,G,B) ##set the color value
print('Red=%d, Green = %d, Blue = %d' %(R, G, B))
sleep(0.2)
##stop pwm
pwm_R.stop()
pwm_G.stop()
pwm_B.stop()
GPIO.cleanup() ##release all GPIO
Project 7：Flow Light
Description：
What is flow light? Maybe you see it on the wall of buildings and billboards. It is a scene that LED gradually brightens then darkens one by one.
Components：
|
|
|
|
|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
|
|
|
|
LED - Red *8 |
220Ω Resistor*8 |
Jumper Wires |
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 7_LED_Chasing_Effect.py
Test Result：
Eight LED lights change from light to dark then back to dark, one by one.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
import RPi.GPIO as GPIO
from time import sleep
##LED pin
led1 = 18
led2 = 23
led3 = 24
led4 = 25
led5 = 12
led6 = 16
led7 = 20
led8 = 21
GPIO.setmode(GPIO.BCM) ## use BCM numbers
##set the ledPin OUTPUT mode
GPIO.setup(led1,GPIO.OUT)
GPIO.setup(led2,GPIO.OUT)
GPIO.setup(led3,GPIO.OUT)
GPIO.setup(led4,GPIO.OUT)
GPIO.setup(led5,GPIO.OUT)
GPIO.setup(led6,GPIO.OUT)
GPIO.setup(led7,GPIO.OUT)
GPIO.setup(led8,GPIO.OUT)
while True:
##Led lights are lit one by one
GPIO.output(led1,GPIO.HIGH)
sleep(0.2) ## the delay size to control the speed of the water lamp
GPIO.output(led2,GPIO.HIGH)
sleep(0.2)
GPIO.output(led3,GPIO.HIGH)
sleep(0.2)
GPIO.output(led4,GPIO.HIGH)
sleep(0.2)
GPIO.output(led5,GPIO.HIGH)
sleep(0.2)
GPIO.output(led6,GPIO.HIGH)
sleep(0.2)
GPIO.output(led7,GPIO.HIGH)
sleep(0.2)
GPIO.output(led8,GPIO.HIGH)
sleep(0.2)
##Led lights go out one by one
GPIO.output(led8,GPIO.LOW)
sleep(0.2)
GPIO.output(led7,GPIO.LOW)
sleep(0.2)
GPIO.output(led6,GPIO.LOW)
sleep(0.2)
GPIO.output(led5,GPIO.LOW)
sleep(0.2)
GPIO.output(led4,GPIO.LOW)
sleep(0.2)
GPIO.output(led3,GPIO.LOW)
sleep(0.2)
GPIO.output(led2,GPIO.LOW)
sleep(0.2)
GPIO.output(led1,GPIO.LOW)
sleep(0.2)
GPIO.cleanup() ##release all GPIO
Project 8：Doorbell
Description：
In this project, we will demonstrate how doorbell works.
Components：
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|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
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|
Active Buzzer *1 |
Jumper Wires |
10KΩ Resistor*1 |
Button Switch *1 |
Components Knowledge:
Active buzzer：
An active buzzer will generate a tone using an internal oscillator, so all that is needed is a DC voltage. A passive buzzer requires an AC signal to make a sound. It is like an electromagnetic speaker, where a changing input signal produces the sound, rather than producing a tone automatically.
As a type of electronic buzzer with integrated structure, buzzers, which are supplied by DC power, are widely used in computers, printers, photocopiers, alarms, electronic toys, automotive electronic devices, telephones, timers and other electronic products for voice devices. Buzzers can be categorized as active and passive ones (see the following picture). Turn the pins of two buzzers face up, and the one with a green circuit board is a passive buzzer, while the other enclosed with a black tape is an active one.
Button switch: it can control circuit. Before pressed, the current can’t pass from one end to the other end. Both ends are like two mountains. There is a river in between. We can’t cross this mountain to another mountain. When pressed, my internal metal piece is connecting the two sides to let the current pass, just like building a bridge to connect the two mountains.
Inner structure:
1 and 1 , 2 and 2 are connected , however, 1 and 2 are disconnected when the button is not pressed; 1 and 2 are connected when pressing the button.
10KΩ resistor：
It is pull-up resistor. The high and low levels of Raspberry Pi will be unstable if connecting only GPIO pins instead of resistors.
Resistor could stabilize the electronic signal and protect circuit.
The circuit will be shorten and components will be burnt if without wiring 10kΩ resistor.
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”.
cd /home/pi/pythonCode_A
python 8_active_buzzer.py
Test Result：
Press button, the buzzer emits sound, otherwise, it doesn’t.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
import RPi.GPIO as GPIO
from time import sleep
##active buzzer pin
buzPin = 27
##button pin
btnPin = 18
GPIO.setmode(GPIO.BCM) ## use BCM numbers
GPIO.setup(buzPin,GPIO.OUT) ##set buzPin OUTPUT mode
GPIO.setup(btnPin,GPIO.IN,GPIO.PUD_UP) ## set btnPin INPUT mode
while True:
val = GPIO.input(btnPin)
print(val);
if(val == 0): ##Judge whether the button is pressed
GPIO.output(buzPin,GPIO.HIGH) ##Buzzer ring
else:
GPIO.output(buzPin,GPIO.LOW) ##buzzer off
GPIO.cleanup() ## Release all GPIO
Project 9：Passive Buzzer
Description：
We will conduct an interesting experiment—–control passive buzzer to compose a song.
Components：
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|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
|
|
|
Breadboard*1 |
Passive Buzzer *1 |
Jumper Wires |
Component Knowledge
Passive buzzer：
Passive buzzer is a type of electronic buzzer with integrated structure.
Buzzers can be categorized as active and passive ones (see the following picture).
An active buzzer has a built-in oscillating source, so it will make sounds when electrified. But a passive buzzer does not have such source, so it will not tweet if DC signals are used; instead, you need to use square waves whose frequency is between 2K and 5K to drive it. The active buzzer is often more expensive than the passive one because of multiple built-in oscillating circuits.
Turn the pins of two buzzers face up, and the one with a green circuit board is a passive buzzer, while the other enclosed with a black tape is an active one, as shown:
Passive buzzer provides alternating current to sound coils to make electronic magnet and permanent magnet attraction or repulsion so as to push vibration film to emit sound, according to electromagnetic induction.
Only certain frequency with high and low levels can make passive buzzer emit sound, since DC current only makes vibration film vibrated continuously rather than producing sound.
Schematic and Connection Diagram
Run Example Code 1：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 9.1_passive_buzzer.py
Test Result 1：
Passive emits“tick,tick”sound.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code 1：
##!/usr/bin/env python
## -*- coding: utf-8 -*-
import time
import RPi.GPIO as GPIO
buzPin = 18
i1 = 0
i2 = 0
GPIO.setmode(GPIO.BCM)
GPIO.setup(buzPin, GPIO.OUT)
try:
while 1: ##loop
while(i1<50):
GPIO.output(buzPin,GPIO.HIGH)
time.sleep(0.001) ##wait for 1 ms
GPIO.output(buzPin,GPIO.LOW)
time.sleep(0.001)
i1 = i1 + 1
time.sleep(0.3)
while(i2<50):
GPIO.output(buzPin,GPIO.HIGH)
time.sleep(0.001) ##wait for 1 ms
GPIO.output(buzPin,GPIO.LOW)
time.sleep(0.001)
i2 = i2 + 1
time.sleep(1)
i1 = 0
i2 = 0
except KeyboardInterrupt:
pass
p.stop() ##stop pwm
GPIO.cleanup() ##release all GPIO
Run Example Code 2：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 9.2_passive_buzzer.py
Test Result 2：
Passive buzzer plays a “Happy Birthday”song.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code 2：
## -*- coding: utf-8 -*-
import RPi.GPIO as GPIO
import time
Buzzer = 18 ## set the Pin
## Happy birthday
Do = 262
Re = 294
Mi = 330
Fa = 349
Sol = 392
La = 440
Si = 494
Do_h = 523
Re_h = 587
Mi_h = 659
Fa_h = 698
Sol_h = 784
La_h = 880
Si_h = 988
## The tune
song_1 = [
Sol,Sol,La,Sol,Do_h,Si,
Sol,Sol,La,Sol,Re_h,Do_h,
Sol,Sol,Sol_h,Mi_h,Do_h,Si,La,
Fa_h,Fa_h,Mi_h,Do_h,Re_h,Do_h
]
## delay
beat_1 = [
0.5,0.5,1,1,1,1+1,
0.5,0.5,1,1,1,1+1,
0.5,0.5,1,1,1,1,1,
0.5,0.5,1,1,1,1+1,
]
def setup():
GPIO.setmode(GPIO.BCM) ## Numbers GPIOs by physical location
GPIO.setup(Buzzer, GPIO.OUT) ## Set pins' mode is output
global Buzz ## Assign a global variable to replace GPIO.PWM
Buzz = GPIO.PWM(Buzzer, 440) ## 440 is initial frequency.
Buzz.start(50) ## Start Buzzer pin with 50% duty ration
def loop():
while True:
print('\n Playing song 3...')
for i in range(0, len(song_1)): ## Play song 1
Buzz.ChangeFrequency(song_1[i]) ## Change the frequency along the song note
time.sleep(beat_1[i] * 0.5) ## delay a note for beat * 0.5s
def destory():
Buzz.stop() ## Stop the buzzer
GPIO.output(Buzzer, 1) ## Set Buzzer pin to High
GPIO.cleanup() ## Release resource
if __name__ == '__main__': ## Program start from here
setup()
try:
loop()
except KeyboardInterrupt: ## When 'Ctrl+C' is pressed, the child program destroy() will be executed.
destory()
Project 10：1-Digit 7 Segment LED Display
Description：
To make LED display numbers, human being invented digital display, in this lesson, we will learn how to control digital display.
Components：
|
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|
|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
|
|
|
|
1-digit 7-seg LED*1 |
220ΩResistor*8 |
Jumper Wires |
Component Knowledge：
LED display：
LED segment display is a semiconductor light-emitting device. Its basic unit is a light-emitting diode (LED).
For the common anode display, connect the common anode (COM) to +5V. When the cathode level of a certain segment is low, the segment is on; when the cathode level of a certain segment is high, the segment is off.
For the common cathode display, connect the common cathode (COM) to GND. When the anode level of a certain segment is high, the segment is on; when the anode level of a certain segment is low, the segment is off.
Each segment of the display consists of an LED. So when you use it, you also need to use a current-limiting resistor. Otherwise, LED will be burnt out.
When using 1-digit 7-segment display please notice that if it is common anode, the common anode pin connects to the power source; if it is common cathode, the common cathode pin connects to the GND.
Each of the LEDs in the display is given a positional segment with one of its connection pins led out from the rectangular plastic package. These LED pins are labeled from “a” through to “g” representing each individual LED.
Below is the seven-segment pin diagram.
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 10_one-digital-LED.py
Test Result：
LED display shows0~9，in loop way.
Note: Press Ctrl + C on keyboard and exit code running
Example Code：
import RPi.GPIO as GPIO
from time import sleep
## led pin
a = 23
b = 18
c = 6
d = 13
e = 19
f = 24
g = 25
dp = 5
GPIO.setmode(GPIO.BCM) ##use BCM numbers
##set the Pin OUTPUT mode
GPIO.setup(a,GPIO.OUT)
GPIO.setup(b,GPIO.OUT)
GPIO.setup(c,GPIO.OUT)
GPIO.setup(d,GPIO.OUT)
GPIO.setup(e,GPIO.OUT)
GPIO.setup(f,GPIO.OUT)
GPIO.setup(g,GPIO.OUT)
GPIO.setup(dp,GPIO.OUT)
## display 0
def d_0():
GPIO.output(a,GPIO.HIGH)
GPIO.output(b,GPIO.HIGH)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.HIGH)
GPIO.output(e,GPIO.HIGH)
GPIO.output(f,GPIO.HIGH)
GPIO.output(g,GPIO.LOW)
GPIO.output(dp,GPIO.LOW)
def d_1(): ## display 1
GPIO.output(a,GPIO.LOW)
GPIO.output(b,GPIO.HIGH)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.LOW)
GPIO.output(e,GPIO.LOW)
GPIO.output(f,GPIO.LOW)
GPIO.output(g,GPIO.LOW)
GPIO.output(dp,GPIO.LOW)
def d_2(): ## display 2
GPIO.output(a,GPIO.HIGH)
GPIO.output(b,GPIO.HIGH)
GPIO.output(c,GPIO.LOW)
GPIO.output(d,GPIO.HIGH)
GPIO.output(e,GPIO.HIGH)
GPIO.output(f,GPIO.LOW)
GPIO.output(g,GPIO.HIGH)
GPIO.output(dp,GPIO.LOW)
def d_3(): ## display 4
GPIO.output(a,GPIO.HIGH)
GPIO.output(b,GPIO.HIGH)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.HIGH)
GPIO.output(e,GPIO.LOW)
GPIO.output(f,GPIO.LOW)
GPIO.output(g,GPIO.HIGH)
GPIO.output(dp,GPIO.LOW)
def d_4():
GPIO.output(a,GPIO.LOW)
GPIO.output(b,GPIO.HIGH)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.LOW)
GPIO.output(e,GPIO.LOW)
GPIO.output(f,GPIO.HIGH)
GPIO.output(g,GPIO.HIGH)
GPIO.output(dp,GPIO.LOW)
def d_5():
GPIO.output(a,GPIO.HIGH)
GPIO.output(b,GPIO.LOW)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.HIGH)
GPIO.output(e,GPIO.LOW)
GPIO.output(f,GPIO.HIGH)
GPIO.output(g,GPIO.HIGH)
GPIO.output(dp,GPIO.LOW)
def d_6():
GPIO.output(a,GPIO.HIGH)
GPIO.output(b,GPIO.LOW)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.HIGH)
GPIO.output(e,GPIO.HIGH)
GPIO.output(f,GPIO.HIGH)
GPIO.output(g,GPIO.HIGH)
GPIO.output(dp,GPIO.LOW)
def d_7():
GPIO.output(a,GPIO.HIGH)
GPIO.output(b,GPIO.HIGH)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.LOW)
GPIO.output(e,GPIO.LOW)
GPIO.output(f,GPIO.LOW)
GPIO.output(g,GPIO.LOW)
GPIO.output(dp,GPIO.LOW)
def d_8():
GPIO.output(a,GPIO.HIGH)
GPIO.output(b,GPIO.HIGH)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.HIGH)
GPIO.output(e,GPIO.HIGH)
GPIO.output(f,GPIO.HIGH)
GPIO.output(g,GPIO.HIGH)
GPIO.output(dp,GPIO.LOW)
def d_9():
GPIO.output(a,GPIO.HIGH)
GPIO.output(b,GPIO.HIGH)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.HIGH)
GPIO.output(e,GPIO.LOW)
GPIO.output(f,GPIO.HIGH)
GPIO.output(g,GPIO.HIGH)
GPIO.output(dp,GPIO.LOW)
print("test...")
while True:
d_0() ##Call function showing 0
sleep(1) ##delay 1s
d_1()
sleep(1)
d_2()
sleep(1)
d_3()
sleep(1)
d_4()
sleep(1)
d_5()
sleep(1)
d_6()
sleep(1)
d_7()
sleep(1)
d_8()
sleep(1)
d_9()
sleep(1)
GPIO.cleanup() ##realese all GPIO
Project 11：4-Digit Segment LED Display
Description：
In previous lesson, the LED display only shows 1 digit number, whereas, we could try to operate 4-digit segment LED display.
Components：
|
|
|
|
|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
|
|
|
|
4-digit 7-seg LED*1 |
220Ω Resistor*8 |
Jumper Wires |
Component Knowledge
digit LED display:
The 4-digit LED display is divided into common anode and common cathode. Similar to 1-digit segment LED display, it is controlled display segment by 8 GPIO ports(8 LED lights). However, this is 4 digit display, 4 GPIO ports are required to control the bit selection terminal.
Ours is common cathode.
4-digit LED Display Pinout.Pin 1, 2, 3 and 4 are control pin of control bit.
Schematic Diagram
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 11_four-digital-LED.py
Test Result：
4-digit LED display firstly shows“0000”, then plus 1 every time until it reaches“9999”, however, when “9999” adds 1, the value changes into“0000”.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
## -*- coding:utf-8 -*-
import RPi.GPIO as GPIO
from time import sleep
from threading import Timer ##Library files for introducing timers
d_num = 0
b_num = 0
##Pin of each section of nixie tube
a = 24
b = 18
c = 6
d = 19
e = 26
f = 23
g = 5
dp = 13
##Pin of each digit of nixie tube
d1 = 4
d2 = 17
d3 = 27
d4 = 22
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
##set as output
GPIO.setup(a,GPIO.OUT)
GPIO.setup(b,GPIO.OUT)
GPIO.setup(c,GPIO.OUT)
GPIO.setup(d,GPIO.OUT)
GPIO.setup(e,GPIO.OUT)
GPIO.setup(f,GPIO.OUT)
GPIO.setup(g,GPIO.OUT)
GPIO.setup(dp,GPIO.OUT)
##set as output
GPIO.setup(d1,GPIO.OUT)
GPIO.setup(d2,GPIO.OUT)
GPIO.setup(d3,GPIO.OUT)
GPIO.setup(d4,GPIO.OUT)
##Set to high level, turn off the nixie tube
GPIO.output(d1,GPIO.HIGH)
GPIO.output(d2,GPIO.HIGH)
GPIO.output(d3,GPIO.HIGH)
GPIO.output(d4,GPIO.HIGH)
def d_0(): ##display 0
GPIO.output(a,GPIO.HIGH)
GPIO.output(b,GPIO.HIGH)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.HIGH)
GPIO.output(e,GPIO.HIGH)
GPIO.output(f,GPIO.HIGH)
GPIO.output(g,GPIO.LOW)
GPIO.output(dp,GPIO.LOW)
def d_1(): ##display 1
GPIO.output(a,GPIO.LOW)
GPIO.output(b,GPIO.HIGH)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.LOW)
GPIO.output(e,GPIO.LOW)
GPIO.output(f,GPIO.LOW)
GPIO.output(g,GPIO.LOW)
GPIO.output(dp,GPIO.LOW)
def d_2(): ##display 2
GPIO.output(a,GPIO.HIGH)
GPIO.output(b,GPIO.HIGH)
GPIO.output(c,GPIO.LOW)
GPIO.output(d,GPIO.HIGH)
GPIO.output(e,GPIO.HIGH)
GPIO.output(f,GPIO.LOW)
GPIO.output(g,GPIO.HIGH)
GPIO.output(dp,GPIO.LOW)
def d_3():
GPIO.output(a,GPIO.HIGH)
GPIO.output(b,GPIO.HIGH)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.HIGH)
GPIO.output(e,GPIO.LOW)
GPIO.output(f,GPIO.LOW)
GPIO.output(g,GPIO.HIGH)
GPIO.output(dp,GPIO.LOW)
def d_4():
GPIO.output(a,GPIO.LOW)
GPIO.output(b,GPIO.HIGH)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.LOW)
GPIO.output(e,GPIO.LOW)
GPIO.output(f,GPIO.HIGH)
GPIO.output(g,GPIO.HIGH)
GPIO.output(dp,GPIO.LOW)
def d_5():
GPIO.output(a,GPIO.HIGH)
GPIO.output(b,GPIO.LOW)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.HIGH)
GPIO.output(e,GPIO.LOW)
GPIO.output(f,GPIO.HIGH)
GPIO.output(g,GPIO.HIGH)
GPIO.output(dp,GPIO.LOW)
def d_6():
GPIO.output(a,GPIO.HIGH)
GPIO.output(b,GPIO.LOW)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.HIGH)
GPIO.output(e,GPIO.HIGH)
GPIO.output(f,GPIO.HIGH)
GPIO.output(g,GPIO.HIGH)
GPIO.output(dp,GPIO.LOW)
def d_7():
GPIO.output(a,GPIO.HIGH)
GPIO.output(b,GPIO.HIGH)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.LOW)
GPIO.output(e,GPIO.LOW)
GPIO.output(f,GPIO.LOW)
GPIO.output(g,GPIO.LOW)
GPIO.output(dp,GPIO.LOW)
def d_8():
GPIO.output(a,GPIO.HIGH)
GPIO.output(b,GPIO.HIGH)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.HIGH)
GPIO.output(e,GPIO.HIGH)
GPIO.output(f,GPIO.HIGH)
GPIO.output(g,GPIO.HIGH)
GPIO.output(dp,GPIO.LOW)
def d_9():
GPIO.output(a,GPIO.HIGH)
GPIO.output(b,GPIO.HIGH)
GPIO.output(c,GPIO.HIGH)
GPIO.output(d,GPIO.HIGH)
GPIO.output(e,GPIO.LOW)
GPIO.output(f,GPIO.HIGH)
GPIO.output(g,GPIO.HIGH)
GPIO.output(dp,GPIO.LOW)
def b_show(bit): ##Choose which digital tube to turn on
##Choose to activate the single-digit digital tube,
##which is the right-most digit of the 4-digit digital tube
if(bit == 0):
GPIO.output(d1,GPIO.LOW)
GPIO.output(d2,GPIO.HIGH)
GPIO.output(d3,GPIO.HIGH)
GPIO.output(d4,GPIO.HIGH)
if(bit == 1): ##Select the start digit digital tube
GPIO.output(d1,GPIO.HIGH)
GPIO.output(d2,GPIO.LOW)
GPIO.output(d3,GPIO.HIGH)
GPIO.output(d4,GPIO.HIGH)
if(bit == 2): ##Select the digital tube that activates the hundreds digit number
GPIO.output(d1,GPIO.HIGH)
GPIO.output(d2,GPIO.HIGH)
GPIO.output(d3,GPIO.LOW)
GPIO.output(d4,GPIO.HIGH)
if(bit == 3): ##Select the digital tube to activate thousands of digits
GPIO.output(d1,GPIO.HIGH)
GPIO.output(d2,GPIO.HIGH)
GPIO.output(d3,GPIO.HIGH)
GPIO.output(d4,GPIO.LOW)
def recongnition(num):
if(num == 0): ##num = 0
d_0() ##Call d_0() to display 0 on the digital tube
if(num == 1):
d_1()
if(num == 2):
d_2()
if(num == 3):
d_3()
if(num == 4):
d_4()
if(num == 5):
d_5()
if(num == 6):
d_6()
if(num == 7):
d_7()
if(num == 8):
d_8()
if(num == 9):
d_9()
def display():
global b_num
if(b_num == 0): ##The ones place, the one on the far right of the 4-digit digital tube
ge = d_num%10 ## So % is the cooperations, so for example, 1356%10 = 6, so you get the units digit of 1356
recongnition(ge) ##This function, called recongnition(), is the number displayed around the digital tube, at d_num=1356, which is 6
b_show(0) ##Call the function b_show(), which controls the nibbit, so that the units digit is the rightmost digit that can be lit
if(b_num == 1): ##ten
shi = d_num%100 ##I'm going to subtract the hundreds place，1356 % 100 = 56
shi = shi/10 ## 56 / 10 = 5 ，You get ten digits
recongnition(shi)
b_show(1) ##Enable the ten digit digital tube to be lit
if(b_num == 2): ##A one hundred - bit
bai = d_num%1000 ##Let's leave out the thousands first, for example：1356 % 1000 = 356 ，So we get rid of the 1
bai = bai/100 ##Then,356 / 100 = 3，The integers are equal to 3, so you get the hundreds
recongnition(bai)
b_show(2) ##So that the hundreds digit digital tube can be lit
if(b_num == 3): ##A one thousand - bit
qian = d_num/1000 ## 1356 / 1000 = 1 ，We get thousands
recongnition(qian)
b_show(3) ##So that the digital tube in the thousands can be lit
b_num = b_num + 1 ##b_num add 1，In order to show you all the numbers
if(b_num >3): ##Since the digital tube is four bits, the limit cannot be greater than three
b_num = 0 ##Greater than 3 is equal to 0
t = Timer(timer_interval,display) ##
t.start()
timer_interval = 0.005 ##Start the timer interrupt every 0.005 seconds
t = Timer(timer_interval,display) ##Timer() is the Timer function, which means display is executed every 0.005s
t.start() ##On timer
print("test...")
while True:
for num in range(0,10000): ##display 0~10000
d_num = num ##num = d_num
print(d_num) ##Terminal print out : d_num
sleep(1) ##delay 1s
GPIO.cleanup() ##release all GPIO
Explanation：
from threading import Timer
Import Timer from“threading”
start() enables“Timer”, cancel() means stopping“Timer”
t = Timer(timer_interval,display)
This is a timer“t”，timer_interval is the time interval of triggering timer function, for instance, timer_interval = 0.005，that means trigger”display”function each 0.005s
threading module library:
Project 12：8*8 Dot Matrix
Description：
In this chapter, let’s get down with a 8x8 LED dot matrix
Components：
|
|
|
|
|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
|
|
|
|
8*8 LED Matrix*1 |
220Ω Resistor*8 |
Jumper Wires |
Component Knowledge
8*8 LED Matrix：
8×8 matrix consists of 64 dots or pixels. There is a LED for each pixel and these LEDs are connected to total of 16 pins.
Generally, there are two types of dot matrix – common cathode and common anode.
Schematic Diagram：
Working Principle：
8*8 is composed of LEDs. It will turn on if the positive is high level and negative is low level.
For the above figure, the first LED will be on if setting Y0(0) to HIGH and the rest of pins to LOW, X0(A) to LOW and the rest one to HIGH.
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 12_Matrix-LED.py
Test Result：
The dot on 8*8 dot matrix module gradually turns on until to full screen and then off.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
## -*- coding:utf-8 -*-
import RPi.GPIO as GPIO
from time import sleep
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
##Define the pin of the row
row1 = 27
row2 = 4
row3 = 5
row4 = 17
row5 = 26
row6 = 6
row7 = 19
row8 = 13
##Define the pins of the column
col1 = 24
col2 = 16
col3 = 20
col4 = 18
col5 = 21
col6 = 23
col7 = 25
col8 = 12
##Set to output
GPIO.setup(row1,GPIO.OUT)
GPIO.setup(row2,GPIO.OUT)
GPIO.setup(row3,GPIO.OUT)
GPIO.setup(row4,GPIO.OUT)
GPIO.setup(row5,GPIO.OUT)
GPIO.setup(row6,GPIO.OUT)
GPIO.setup(row7,GPIO.OUT)
GPIO.setup(row8,GPIO.OUT)
GPIO.setup(col1,GPIO.OUT)
GPIO.setup(col2,GPIO.OUT)
GPIO.setup(col3,GPIO.OUT)
GPIO.setup(col4,GPIO.OUT)
GPIO.setup(col5,GPIO.OUT)
GPIO.setup(col6,GPIO.OUT)
GPIO.setup(col7,GPIO.OUT)
GPIO.setup(col8,GPIO.OUT)
##Sets the pin of the column to low level
GPIO.output(col1,GPIO.LOW)
GPIO.output(col2,GPIO.LOW)
GPIO.output(col3,GPIO.LOW)
GPIO.output(col4,GPIO.LOW)
GPIO.output(col5,GPIO.LOW)
GPIO.output(col6,GPIO.LOW)
GPIO.output(col7,GPIO.LOW)
GPIO.output(col8,GPIO.LOW)
##Since the column of the lattice has been set to low level,
##the corresponding row of the lattice will light up when the pin of the row is at high level
def Row(d):
if(d ==1):
GPIO.output(row1,GPIO.HIGH) ##Light the first line
if(d ==2):
GPIO.output(row2,GPIO.HIGH) ##Light the second line
if(d ==3):
GPIO.output(row3,GPIO.HIGH)
if(d ==4):
GPIO.output(row4,GPIO.HIGH)
if(d ==5):
GPIO.output(row5,GPIO.HIGH)
if(d ==6):
GPIO.output(row6,GPIO.HIGH)
if(d ==7):
GPIO.output(row7,GPIO.HIGH)
if(d ==8):
GPIO.output(row8,GPIO.HIGH)
##Close the lattice
def off():
GPIO.output(row1,GPIO.LOW)
GPIO.output(row2,GPIO.LOW)
GPIO.output(row3,GPIO.LOW)
GPIO.output(row4,GPIO.LOW)
GPIO.output(row5,GPIO.LOW)
GPIO.output(row6,GPIO.LOW)
GPIO.output(row7,GPIO.LOW)
GPIO.output(row8,GPIO.LOW)
print("test...")
while True:
for num in range(1,10): ##Light the lattice line by line
Row(num)
if(num == 9): ##Because the lattice has only 8 rows, and I'm limiting it here, is equal to 9
off() ##Close the lattice
sleep(0.2)
GPIO.cleanup() ##Release all GPIO ports
Project 13：74HC595
Description：
In previous lesson, we control a 1-digit LED display with eight, which is wasteful. We need to figure out a method to save the use of GPIO ports. In fact, we need a 74HC595 CHIP.
Components：
|
|
|
|
|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
|
|
|
|
1-digit 7- seg LED*1 |
220Ω Resistor*8 |
74HC595N*1 |
Jumper Wires |
Component Knowledge
74HC595：
The 74HC595 consists of an 8−bit shift register and an 8−bit D−typelatch with three−state parallel outputs. The shift register accepts serial data and provides a serial output. The shift register also provides parallel data to the 8−bit latch. The shift register and latch have independent clock inputs. This device also has an asynchronous reset for the shift register.
74HC595 Control Protocol
PIN |
FUNCTION |
|---|---|
13 PIN OE |
Enable pin, not controlled by program when high level; make it connect to GND when low level |
14 PIN SI |
This is pin receiving data, enter a bit each time and compose a byte if inputting eight times |
10 PIN SCLK |
Shift register clear pin, used to clear out all data in shift register, when low level, data will be cleared out. |
11 PIN SCK |
Clock pin of shift register, the data inside will move backward and receive the data input when it is on rising edge. |
12 PIN RCK |
Clock input pin of latch register, data from shift register will saved in latch register when it is on rising edge. |
9 Pin SQH |
Cascade pin，connected to multiple 74HC595 chips |
More details about 74HC595 chip, you could look through chip specification folder.
Schematic Diagram：
The output end QA~QH of 74HC595 respond to the pin DP, and g~a.
Why? Since the binary is counted from the right, programming will be convenient. For example, 1-digit display shows 0011 1111 , the first bit is 1 which equals to QA saved in 74HC595, then when the rest numbers are sent to 74HC595, 1 will be pushed to QH, and last bit 0 is placed on QA. However, the wiring is so inverse that the first bit of binary corresponds to a and last one to DIP controlling 1-digit display.
74HC595 |
|||||||||
|---|---|---|---|---|---|---|---|---|---|
QH |
QG |
QF |
QE |
QD |
QC |
QB |
QA |
||
a |
b |
c |
d |
e |
f |
g |
dp |
||
0 |
1 |
1 |
1 |
1 |
1 |
1 |
0 |
0 |
252 |
1 |
0 |
1 |
1 |
0 |
0 |
0 |
0 |
0 |
96 |
2 |
1 |
1 |
0 |
1 |
1 |
0 |
1 |
0 |
218 |
3 |
1 |
1 |
1 |
1 |
0 |
0 |
1 |
0 |
242 |
4 |
0 |
1 |
1 |
0 |
0 |
1 |
1 |
0 |
102 |
5 |
1 |
0 |
1 |
1 |
0 |
1 |
1 |
0 |
182 |
6 |
1 |
0 |
1 |
1 |
1 |
1 |
1 |
0 |
190 |
7 |
1 |
1 |
1 |
0 |
0 |
0 |
0 |
0 |
224 |
8 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
0 |
254 |
9 |
1 |
1 |
1 |
1 |
0 |
1 |
1 |
0 |
246 |
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 13_74HC595.py
Test Result：
1-digit seven segment display shows 0~9
Note: Press Ctrl + C on keyboard and exit code running
Example Code：
import RPi.GPIO as GPIO
from time import sleep
##define 74Hc595 pin
data = 17 ##Serial digital input pin
rck = 27
sck = 22
##These hexadecimal numbers show data from 0 to 9
##Hexadecimal to binary,0x3F, 0011 1111
num = [0x3F, 0x06, 0x5B, 0x4F, 0x66, 0x6D, \
0x7D, 0x07, 0x7F, 0x6F]
GPIO.setmode(GPIO.BCM) ##use BCM numbers
##set the 74HC595 Pin OUTPUT mode
GPIO.setup(data,GPIO.OUT)
GPIO.setup(rck,GPIO.OUT)
GPIO.setup(sck,GPIO.OUT)
##Set rck and sck to high first
GPIO.output(rck,GPIO.HIGH)
GPIO.output(sck,GPIO.HIGH)
def bitshift(dat):
if dat == 0:
da = num[0]
if dat == 1:
da = num[1]
if dat == 2:
da = num[2]
if dat == 3:
da = num[3]
if dat == 4:
da = num[4]
if dat == 5:
da = num[5]
if dat == 6:
da = num[6]
if dat == 7:
da = num[7]
if dat == 8:
da = num[8]
if dat == 9:
da = num[9]
for a in range(0,8):
GPIO.output(sck,GPIO.LOW) ##set sckPin LOW
if (da & 0x01) == 0x01: ##Judge whether the last bit is 1
GPIO.output(data,GPIO.HIGH) ##1
else:
GPIO.output(data,GPIO.LOW) ##0
##set sckPin HIGH , Move data to shift register
GPIO.output(sck,GPIO.HIGH)
##Move data one bit to the right
da =da >> 1
def display(num):
##Clock pin of storage register is set to low level
GPIO.output(rck,GPIO.LOW)
##function, receive data
bitshift(num)
##Clock pin of storage register is set to high level
##At this time, the data will be output from the Q0 ~ Q7 port
GPIO.output(rck,GPIO.HIGH)
print("test...")
while True:
for a in range(0,10): ##display 0~9
display(a)
sleep(1)
GPIO.cleanup()
Project 14：Button-controlled LED
Description：
Usually, a complete open loop control is made of external information input. Controller and actuator.
The external information is input into controller which can analyze the input data and send to control signals to make actuator to react.
A button-controlled LED is decided by an open loop control. Next, we will make a desk lamp with a button, an LED and RPi. LED is on when button is pressed, on the contrary, it will be off.
Components：
|
|
|
|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
|
|
|
Breadboard*1 |
LED - Red *1 |
Button Switch *1 |
|
|
|
220Ω Resistor*1 |
Jumper Wires |
10KΩ Resistor*1 |
Schematic Diagram：
Eliminate Button Shaking
The LED status won’t jump into new state immediately when button is pressed. There will be a short continuous shaking before into new status, which is similar with release status.
Therefore, there will be many a presses and release actions. The shaking will misleads the high speed movement of MCU, causing wrong judgement. That requires that we need to judge the button’ status frequently.
The button means being pressed when its status is stable.
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 14_button_led.py
Test Result：
Press button, LED turns on, press again, LED is off.
Note: Press Ctrl + C on keyboard and exit code running
Example Code：
import RPi.GPIO as GPIO
from time import sleep
LED = 27 ##set ledPin
button = 18 ##set buttonPin
val = 0 ##Button variables
count = 0 ##Record the number of button presses
flag = 0 ##Odd even variable
GPIO.setmode(GPIO.BCM) ## use BCM numbers
GPIO.setup(LED,GPIO.OUT) ##set the ledPin OUTPUT mode
GPIO.setup(button,GPIO.IN,GPIO.PUD_UP) ##set the buttonPin INPUT mode and buttonPin to PULL UP
while True:
val = GPIO.input(button) ##Receive button value
##print("button = %d"%(val))
if(val == 0): ##if button is pressed
sleep(0.01) ##Eliminate button jitter
val = GPIO.input(button) ##Receive button value
if(val == 1): ##Loosen the button
count = count + 1 ##Count the number of clicks on the button
print("count = %d" %count)
flag = count % 2 ##Remainder 2 ,Even is 0, odd is 1
if(flag == 1):
GPIO.output(LED,GPIO.HIGH) ##turn on led
else:
GPIO.output(LED,GPIO.LOW) ##turn off led
GPIO.cleanup() ##release all GPIO
Project 15：Responder
Description：
A responder is someone who answers a question or who acts quickly in response to some event. In this lesson, we will show you how to make a responder and introduce its working principle.
Components：
|
|
|
|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
|
|
|
Breadboard*1 |
LED - Red *1 |
LED - Green*1 |
|
|
|
LED - Yellow*1 |
220Ω Resistor*3 |
Jumper Wires |
|
|
|
10KΩ Resistor*4 |
Button Switch *4 |
Schematic Diagram：
Design Description：
You could assume a scene that three competitors in knowledge quiz.
Everyone has a responder and an LED. Corresponding LED will turn on if one presses his own responder, however, others’ won’t be on. What’s more, a questioner has a button to control their LEDs. After a round of game, LEDs are off, the quiz restarts.
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 15_Responder.py
Test Result：
The corresponding LED will turn on if a competitor press his own responder, but others’ are off. The questioner press a button to turn off their LEDs and restart a new round quiz.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
import RPi.GPIO as GPIO
from time import sleep
## led colour
red = 26
yellow = 19
blue = 13
##set button pin
##Player's button
key1 = 23
key2 = 24
key3 = 25
##Button for the author
reset = 18
flag = True ##One sign quantity for restriction, only one light can be on
GPIO.setmode(GPIO.BCM) ##use BCM numbers
##set the led Pin OUTPUT mode
GPIO.setup(red,GPIO.OUT)
GPIO.setup(yellow,GPIO.OUT)
GPIO.setup(blue,GPIO.OUT)
##set the button pin INPUT mode and PUD_UP
GPIO.setup(key1,GPIO.IN,GPIO.PUD_UP)
GPIO.setup(key2,GPIO.IN,GPIO.PUD_UP)
GPIO.setup(key3,GPIO.IN,GPIO.PUD_UP)
GPIO.setup(reset,GPIO.IN,GPIO.PUD_UP)
while True: ##loop
if not GPIO.input(key1) and flag == True: ##Judge if player 1's button is pressed
GPIO.output(red,GPIO.HIGH)
flag = False
if not GPIO.input(key2) and flag == True: ##Judge if player 2's button is pressed
GPIO.output(yellow,GPIO.HIGH)
flag = False
if not GPIO.input(key3) and flag == True: ##Judge if player 3's button is pressed
GPIO.output(blue,GPIO.HIGH)
flag = False
if not GPIO.input(reset): ##The writer's button is pressed
GPIO.output(red,GPIO.LOW)
GPIO.output(yellow,GPIO.LOW)
GPIO.output(blue,GPIO.LOW)
flag = True
GPIO.cleanup() ##release all GPIO
Project 16：PIR Motion Sensor
Description：
In this lesson, we will learn about PIR motion sensor.
Components：
|
|
|
|
|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
|
|
|
|
PIR Motion Sensor*1 |
LED - Red *1 |
220Ω Resistor*1 |
Jumper Wires |
Component Knowledge
PIR Motion Sensor：
The principle of human infrared sensor is that when certain crystals, such as lithium tantalate and triglyceride sulfate, are heated, the two ends of the crystal will generate an equal number of charges, with opposite signs, which can be converted into voltage output by an amplifier.
Human body will emit IR ray, although weak but can be detected. Sensor will output high level(1) when human being is detected by sensor, otherwise, it will output low level o.
Note: Nothing but moving person can be detected, with the detection distance is up to 3m.
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 16_PIR-led.py
Test Result：
LED will turn on and terminal prints somebody if PIR motion sensor detects people; if not, LED will be off and terminal will print nobody.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code
import RPi.GPIO as GPIO
import time
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
ledPin = 5 ##set led pin
pirPin = 18 ##set PYE-IR pin
GPIO.setup(ledPin,GPIO.OUT)
GPIO.setup(pirPin,GPIO.IN)
while True: ###loop
if GPIO.input(pirPin): ##When someone is detected
GPIO.output(ledPin,GPIO.HIGH) ##turn on the led
print("somebody")
else:
GPIO.output(ledPin,GPIO.LOW) ##turn off led
print("nobody")
GPIO.cleanup()
Project 17：Fire Alarm
Description：
A flame detector is a sensor designed to detect and respond to the presence of a flame or fire, allowing flame detection.
Components：
|
|
|
|
|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
|
|
|
|
Active Buzzer *1 |
Flame Sensor *1 |
10KΩ Resistor*1 |
Jumper Wires |
Component Knowledge
Flame Sensor：
Flame sensor is made based on the principle that infrared ray is highly sensitive to flame. It has an infrared receiving tube specially designed to detect fire, and then convert the flame brightness to fluctuating level signal. The signals are then input into the central processor and be dealt with accordingly.
Flame sensor is used to detect fire source with wavelength in 760nm～1100nm, detection angle is 60°. When its IR waves length is close to 940nm, and its sensitivity is highest.
Notice that keep flame sensor away from fire source to defend its damage for its working temperature is between -25°-85°
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 17_flame_buzzer.py
Test Result：
Buzzer will alarm when detecting fire, otherwise, it will stop emitting sound
Note: Press Ctrl + C on keyboard and exit code running
Example Code：
import RPi.GPIO as GPIO
from time import sleep
##define buzzer pin
buzPin = 27
##define flame Pin
flamePin = 18
val = 0 ##
GPIO.setmode(GPIO.BCM) ##use BCM numbers
GPIO.setup(buzPin,GPIO.OUT) ##set the buzPin OUTPUT
GPIO.setup(flamePin,GPIO.IN,GPIO.PUD_UP) ##set the flamePin INPUT
while True:
val = GPIO.input(flamePin) ##Receives the value of the flame sensor
print("val = %d" %val)
if (val == 1): ##When flame is detected
GPIO.output(buzPin,GPIO.HIGH) ##Buzzer turn on
else:
GPIO.output(buzPin,GPIO.LOW) ##buzzer turn off
GPIO.cleanup() ## Release all GPIO
Project 18：Electronic Hourglass
Description：
An hourglass (or sandglass, sand timer, sand clock or egg timer) is a device used to measure the passage of time. It comprises two glass bulbs connected vertically by a narrow neck that allows a regulated flow of a substance (historically sand) from the upper bulb to the lower one. Typically the upper and lower bulbs are symmetric so that the hourglass will measure the same duration regardless of orientation. The specific duration of time a given hourglass measures is determined by factors including the quantity and coarseness of the particulate matter, the bulb size, and the neck width.
Components：
|
|
|
|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
|
|
|
Breadboard*1 |
LED - Red *2 |
Ball Tilt Sensor*1 |
|
|
|
220Ω Resistor*2 |
10KΩ Resistor*1 |
Jumper Wires |
Component Knowledge
Ball Tilt Sensor：
Tilt sensors (tilt ball switch) allow you to detect orientation or inclination. They are small, inexpensive, low-power and easy-to-use. If used properly, they will not wear out.
The tilt-switch twig is the equivalent of a button, and is used as a digital input. Inside the tilt switch is a ball that make contact with the pins when the case is upright. Tilt the case over and the balls don’t touch, thus not making a connection. When the switch is level it is open, and when tilted, the switch closes.
It can be used for orientation detection, alarm device or others.
Here is the principle of tilt sensor to illustrate how it works:
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 18_ball_Tilt.py
Test Result：
Led 1 gradually brightens and led 2 gradually darkens when place electronic hourglass, however, as you make it upside down, led 1 gradually darkens, led 2 gets bright.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
import RPi.GPIO as GPIO
from time import sleep
##define led pin
led1Pin = 17
led2Pin = 27
##define Ball Tilt Sensor Pin
tiltPin = 18
GPIO.setmode(GPIO.BCM) ##use BCM unmbers
GPIO.setup(led1Pin,GPIO.OUT) ##set the ledPin OUTPUT mode
GPIO.setup(led2Pin,GPIO.OUT)
GPIO.output(led1Pin,GPIO.HIGH) ## make ledPin output HIGH level
GPIO.output(led2Pin,GPIO.LOW) ## make ledPin output LOW level
GPIO.setup(tiltPin,GPIO.IN,GPIO.PUD_UP)
pwm1 = GPIO.PWM(led1Pin,1000) ##create a pwm1 instance
pwm1.start(0) ##start pwm1
pwm2 = GPIO.PWM(led2Pin,1000) ##create a pwm2 instance
pwm2.start(0) ##start pwm2
val1 = 50
val2 = 50
while True:
if not GPIO.input(tiltPin):
val1 = val1 + 1
val2 = val2 - 1
if (val1 >= 100): ##Limit PWM value to no more than 100
val1 = 100
if (val2 < 0): ##Limit PWM value not less than 0
val2 = 0
print("led1 = %1.0f" %(val1))
pwm1.ChangeDutyCycle(val1) ##change the frequency
pwm2.ChangeDutyCycle(val2)
sleep(0.1)
else:
val1 = val1 - 1
val2 = val2 + 1
if (val1 < 0):
val1 = 0
if (val2 >= 100):
val2 = 100
print("led2 = %1.0f" %(val2))
pwm1.ChangeDutyCycle(val1)
pwm2.ChangeDutyCycle(val2)
sleep(0.1)
pwm1.stop() ##stop pwm1
GPIO.cleanup() ##release all GPIO
Project 19：Stepless Dimming
Description：
A stepless dimming control method of a lighting system is applicable to the situations where a light source for a lighting terminal is a fluorescent lamp and/or an LED lamp.
Components：
|
|
|
|
|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
|
|
|
|
Potentiometer*1 |
PCF8591 A/D Converter Module*1 |
Jumper Wires |
Component Knowledge
Keyestudio PCF8591 A/D Converter Module：
Raspberry Pi doesn’t come with AD/DA function. It has to be connected AD/DA shield if it is connected to analog sensor. We use pcf8591 AD/DA converter which adopts iic communication. Therefore, the operation steps are shown below:
a. Enter sudo raspi-config and press “Enter” to navigate the configuration page.
b. Enable the I2C function according to the following pictures( press（↑）,（↓）,（←）,（→）on the keyboard and “Enter”）
You could check more detail about I2C communication agreement in the following link:
https://www.nxp.com/docs/en/user-guide/UM10204.pdf
PCF8591 Pins:
More details about PCF8591 chip, you could look through chip specification folder.
From the below figure, PCF8591 has an analog output pin Aout and four analog input pin A0-A3.
Check the address of iic module（PCF8591）of Raspberry Pi, enter command i2cdetect -y 1 and press Enter.
The iic address of PCF8591 is 0x48.
Used to read the address of pin A0~A3.
The address of analog output pin AOUT: 0x40, that is, 64 converting from hexadecimal to decimal.
A0 = 0x40 ####A0 —-> port address
A1 = 0x41
A2 = 0x42
A3 = 0x43
Adjustable Potentiometer
The rotary potentiometer means the change of resistance.
We could convert the resistance’s change into the voltage’s when setting circuit. Then, voltage changes will be output to GPIO port through module signals.
Wiring according to the below figure and rotate clockwise, resistance value reduces.
Schematic Diagram：
Note: PCF8591 module comes with an LED connected to Aout pint
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 19_potentiometer-LED.py
Test Result：
Terminal prints the analog value read by adjustable potentiometer. The LED brightness will vary with the the rotary of potentiometer.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
import smbus
import time
address = 0x48 ##default address of PCF8591
bus=smbus.SMBus(1) ##Create an instance of smbus
cmd=0x40 ##command
## A0 = 0x40 ###A0 ----> port address
## A1 = 0x41
## A2 = 0x42
## A3 = 0x43
def analogRead(chn): ##read ADC value,chn:0,1,2,3
value = bus.read_byte_data(address,cmd+chn)
return value
def analogWrite(value):##write DAC value
bus.write_byte_data(address,cmd,value)
def loop():
while True:
value = analogRead(0) ##read the ADC value ofchannel 0
analogWrite(value) ##write the DAC value
voltage = value / 255.0 * 3.3 ##calculate the voltage value
print ('ADC Value : %d, Voltage : %.2f'%(value,voltage))
time.sleep(0.01)
def destroy():
bus.close()
if __name__ == '__main__':
print ('Program is starting ... ')
try:
loop()
except KeyboardInterrupt:
destroy()
Explanation：
smbus
Smbus is based on iic communication. We treat it as iic communication library.
bus.read_byte_data(address,cmd+chn)
Read the corresponding modules with iic address，address is the address of pcf8591 module，cmd+chn correspond to the address of analog port pcf8591: A0 = 0x40，A1 = 0x41，A2 = 0x42，A3 = 0x43
bus.write_byte_data(address,cmd,value)
D/A analog value outputs, address is address of pcf8591 module，cmd outputs the address of pins，value: output value.
Smbus library file
Project 20：Photoresistor
Description：
Photo resistor (Photovaristor) is a resistor whose resistance varies according to different incident light strength. It’s made based on the photoelectric effect of semiconductor. In this lesson, let’s explain how it works.
Components：
|
|
|
|
|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
|
|
|
|
LED - Red *1 |
220Ω Resistor*1 |
Photo Resistor*1 |
10KΩ Resistor*1 |
|
|
||
Keyestudio PCF8591 A/D Converter Module*1 |
Jumper Wires |
Component Knowledge
Photoresistor：
Photo resistor (Photovaristor) is a resistor whose resistance varies according to different incident light strength. It’s made based on the photoelectric effect of semiconductor. If the incident light is intense, its resistance reduces; if the incident light is weak, the resistance increases.
If incident light on a photoresistor exceeds a certain frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electrons (and their hole partners) conduct electricity, thereby lowering resistance.
Schematic Diagram：
Run Example Code：
Note: in the experiment, I2C communication is used. We need to check the iic address first( enter command：i2cdetect -y 1 and press “Enter”. If failed, check the wiring is correct or not. If correct, you need to enable I2C communication function of Raspberry Pi, project 19 is for your reference.
After enabling I2C communication, input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 20_photo-resistor.py
Test Result：
Terminal prints the value tested by photoresistor. LED will turn on if the ambient environment is dim, otherwise, LED will be off.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
import RPi.GPIO as GPIO
import smbus
import time
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
led = 5
GPIO.setup(led,GPIO.OUT)
address = 0x48 ###address ---> device address
cmd = 0x40 ###DA converter command
A0 = 0x40 ###A0 ----> port address
A1 = 0x41
A2 = 0x42
A3 = 0x43
bus = smbus.SMBus(1) ###start the bus
def analogRead(count): ##function,read analog data
read_val = bus.read_byte_data(address,cmd+count)
return read_val
while True: ###loop
##Vout = 10 ###10*0.0196=0.196V
##bus.write_byte_data(address,cmd,Vout) ###DA converter
value = analogRead(0) ###read A0 data
if(value<80): ##When the ambient brightness is less than 80, the LED light will be on
GPIO.output(led,GPIO.HIGH)
else:
GPIO.output(led,GPIO.LOW)
print("data:%1.0f" %(value)) ###print data
time.sleep(0.5) ###delay 0.5 second
GPIO.cleanup()
Project 21：Sound-activated Light
Description：
You might find the lights automatically on when you pass them, nevertheless, they will be off if the surrounding is quiet. Do you know why?
Actually, it is sound sensor that controls them on and off.
Components:
|
|
|
|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
|
|
|
Breadboard*1 |
LED - Red *1 |
220Ω Resistor*1 |
|
|
|
Sound Sensor*1 |
Jumper Wires |
Keyestudio PCF8591 A/D Converter Module*1 |
Component Knowledge
A sound sensor is defined as a module that detects sound waves through its intensity and converting it to electrical signals.
The sound sensor has a built-in capacitive electret microphone which is highly sensitive to sound. Sound waves cause the thin film of the electret to vibrate and then the capacitance changes, thus producing the corresponding changed voltage. Since the voltage change is extremely weak, it needs to be amplified. So it is converted into a voltage ranging from 0 to 5V, which is received by data acquisition unit after A/D adapter conversion and then sent to an MCU.
The module can be applied to noise monitoring in traffic artery, and detection of noises within the boundary of industrial enterprises, factories, and construction sites, detection of noises in urban regions, and noise detection and assessment of living surroundings.
Schematic and Connection Diagram：
Run Example Code：
Note: in the experiment, I2C communication is used. We need to check the iic address first( enter command：i2cdetect -y 1 and press“Enter”. If failed, check the wiring is correct or not. If correct, you need to enable I2C communication function of Raspberry Pi, project 19 is for your reference.
After enabling the I2C communication，input the following commands and press “Enter”.
cd /home/pi/pythonCode_A
python 21_sound_led.py
Test Result：
When you clap your hands suddenly, LED lights up and clap again, LED is off.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
import RPi.GPIO as GPIO
import smbus
import time
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
led = 5
GPIO.setup(led,GPIO.OUT)
address = 0x48 ###address ---> device address
cmd = 0x40 ###DA converter command
A0 = 0x40 ###A0 ----> port address
A1 = 0x41
A2 = 0x42
A3 = 0x43
bus = smbus.SMBus(1) ###start the bus
flag = 0
mode = 0
def analogRead(count): ##function,read analog data
read_val = bus.read_byte_data(address,cmd+count)
return read_val
while True: ###loop
value = analogRead(0) ###read A0 data
if(value>50):
flag += 1
mode = flag % 2
if(mode == 0):
GPIO.output(led,GPIO.LOW)
else:
GPIO.output(led,GPIO.HIGH)
print("data:%1.0f" %(value)) ###print data
time.sleep(0.05) ###delay 0.05 second
GPIO.cleanup()
Project 22：LCD1602 & MQ-2 Gas Leakage Alarm
Description：
Some households have access to gas, which is composed of CO, CO2, N2, H2 and CH4. CO is one of toxic gases. People will be in danger if absorbing too much CO. However, we could tackle with this problem over a gas leakage alarm.
Gas MQ-2 leakage alarm detects the presence of a combustible or toxic gas and react by displaying a reading, setting off an audible or visual alarm.
Components：
|
|
|
|
|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
|
|
|
|
Potentiometer*1 |
Active Buzzer *1 |
LCD1602 display*1 |
Analog Gas MQ-2 Sensor * 1 |
|
|
|
|
PCF8591 A/D Converter Module*1 |
Jumper Wires |
M-F Dupont Line |
Component Knowledge
MQ-2 gas sensor adopts the material sensitive to gas——SnO2 with low electricity conductivity. When beset with combustible gas, its electricity conductivity varies with the of the concentration of flammable gas, however, the simple circuit could convert the change of electricity conductivity into the output signals of the concentration of gas sensor.
MQ-2 gas sensor is a multi-purpose and cost-effective. It can detect the concentration of flammable gas and smoke in the range of 300~10000ppm. Meanwhile, it has high sensitivity to natural gas, liquefied petroleum gas and other smoke, especially to alkanes smoke.
LCD1602 LED Display：
It could show the characters or numbers in 16 rows and 2 columns.
1602 LCD Pins:
PIN |
FUNCTION |
|---|---|
Pin 1 |
GND |
Pin 2 |
VCC is connected to positive of 5V |
Pin 3 |
V0 is the contrast adjustment terminal of LCD. The contrast is the weakest when the positive power is connected, and the contrast is the highest when the power is grounded (for high contrast causing double image a 10K potentiometer can help adjust contrast during use) |
Pin 4 |
RS is register selection, select data register when high level 1 and choose command register when low level 0 |
Pin 5 |
RW is reading and writing signal line. Reading operation actives if high level(1)，writing operation actives ig low level(0) |
Pin 6 |
E(EN) is enable end, read information when high level(1), execute the command when low level(0) |
Pin 7~14 |
D0～D7 are 8-bit two-way data ends |
Pin 15 |
Positive of backlight |
Pin 16 |
Negative of backlight |
LCD1602 usually uses eight data cable to provide the data of Data0~Data7, however, it supports“4Bits”mode which is so called four data cables so as to save GPIO ports.
Schematic Diagram：
Run Example Code：
Note: in the experiment, I2C communication is used. We need to check the iic address first( enter command：i2cdetect -y 1 and press“Enter”. If failed, check the wiring is correct or not. If correct, you need to enable I2C communication function of Raspberry Pi, project 19 is for your reference.
After enabling the I2C communication，input the following commands and press “Enter”.
cd /home/pi/pythonCode_A
python 22_LCD1602_MQ2.py
Test Result：
Buzzer alarms when detecting the poisonous gas.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##!/usr/bin/python
##import
import RPi.GPIO as GPIO
import time
import smbus
## Define GPIO to LCD mapping
LCD_RS = 19
LCD_E = 13
LCD_D4 = 22
LCD_D5 = 27
LCD_D6 = 17
LCD_D7 = 4
## Define some device constants
LCD_WIDTH = 16 ## Maximum characters per line
LCD_CHR = True
LCD_CMD = False
LCD_LINE_1 = 0x80 ## LCD RAM address for the 1st line
LCD_LINE_2 = 0xC0 ## LCD RAM address for the 2nd line
## Timing constants
E_PULSE = 0.0005
E_DELAY = 0.0005
##pcf8591
address=0x48
cmd=0x40
A0=0x40###A0---->port address
A1=0x41
A2=0x42
A3=0x43
bus=smbus.SMBus(1)
##buzzer
buzPin = 20 ##set buzPin to 20
GPIO.setmode(GPIO.BCM) ## use BCM numbers
GPIO.setup(buzPin,GPIO.OUT) ##set buzPin OUTPUT mode
def main():
## Main program block
GPIO.setwarnings(False)
GPIO.setmode(GPIO.BCM) ## Use BCM GPIO numbers
GPIO.setup(LCD_E, GPIO.OUT) ## E
GPIO.setup(LCD_RS, GPIO.OUT) ## RS
GPIO.setup(LCD_D4, GPIO.OUT) ## DB4
GPIO.setup(LCD_D5, GPIO.OUT) ## DB5
GPIO.setup(LCD_D6, GPIO.OUT) ## DB6
GPIO.setup(LCD_D7, GPIO.OUT) ## DB7
## Initialise display
lcd_init()
while True:
temp = analogRead(0)
print("MQ-2 = %s"%(temp))
##display
## Send some test
lcd_string("MQ-2",LCD_LINE_1)
lcd_string(temp,LCD_LINE_2)
time.sleep(0.1)
##LM35, require Temperature
def analogRead(count):
read_val=bus.read_byte_data(address,cmd+count)
if(read_val > 60):
GPIO.output(buzPin,GPIO.HIGH) ##Buzzer ring
else:
GPIO.output(buzPin,GPIO.LOW) ##Buzzer stop
mq2_val = str(read_val) ## int to string
return mq2_val
def lcd_init():
## Initialise display
lcd_byte(0x33,LCD_CMD) ## 110011 Initialise
lcd_byte(0x32,LCD_CMD) ## 110010 Initialise
lcd_byte(0x06,LCD_CMD) ## 000110 Cursor move direction
lcd_byte(0x0C,LCD_CMD) ## 001100 Display On,Cursor Off, Blink Off
lcd_byte(0x28,LCD_CMD) ## 101000 Data length, number of lines, font size
lcd_byte(0x01,LCD_CMD) ## 000001 Clear display
time.sleep(E_DELAY)
def lcd_byte(bits, mode):
## Send byte to data pins
## bits = data
## mode = True for character
## False for command
GPIO.output(LCD_RS, mode) ## RS
## High bits
GPIO.output(LCD_D4, False)
GPIO.output(LCD_D5, False)
GPIO.output(LCD_D6, False)
GPIO.output(LCD_D7, False)
if bits&0x10==0x10:
GPIO.output(LCD_D4, True)
if bits&0x20==0x20:
GPIO.output(LCD_D5, True)
if bits&0x40==0x40:
GPIO.output(LCD_D6, True)
if bits&0x80==0x80:
GPIO.output(LCD_D7, True)
## Toggle 'Enable' pin
lcd_toggle_enable()
## Low bits
GPIO.output(LCD_D4, False)
GPIO.output(LCD_D5, False)
GPIO.output(LCD_D6, False)
GPIO.output(LCD_D7, False)
if bits&0x01==0x01:
GPIO.output(LCD_D4, True)
if bits&0x02==0x02:
GPIO.output(LCD_D5, True)
if bits&0x04==0x04:
GPIO.output(LCD_D6, True)
if bits&0x08==0x08:
GPIO.output(LCD_D7, True)
## Toggle 'Enable' pin
lcd_toggle_enable()
def lcd_toggle_enable():
## Toggle enable
time.sleep(E_DELAY)
GPIO.output(LCD_E, True)
time.sleep(E_PULSE)
GPIO.output(LCD_E, False)
time.sleep(E_DELAY)
def lcd_string(message,line):
## Send string to display
message = message.ljust(LCD_WIDTH," ")
lcd_byte(line, LCD_CMD)
for i in range(LCD_WIDTH):
lcd_byte(ord(message[i]),LCD_CHR)
if __name__ == '__main__':
try:
main()
except KeyboardInterrupt:
pass
finally:
lcd_byte(0x01, LCD_CMD)
lcd_string("Goodbye!",LCD_LINE_1)
GPIO.cleanup()
Project 23：Water Level Monitor
Description：
If you have ever had a water heater explode or ever tried to make submersible electronics, then you know how important it is to detect when water is around. Let’s know more about water level sensor.
Components:
|
|
|
|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
|
|
|
Breadboard*1 |
Active Buzzer *1 |
Water sensor * 1 |
|
|
|
PCF8591 A/D Converter Module*1 |
Jumper Wires |
M-F Dupont Line |
Component Knowledge
Water Level Sensor：
Our water sensor is easy- to-use, portable and cost-effective, designed to identify and detect water level and water drop.
This sensor measures the volume of water drop and water quantity through an array of traces of exposed parallel wires.
It could convert water content to analog signals, and output analog value could be used by function of application. It has the features of low consumption as well.
Schematic and Connection Diagram：
Run Example Code：
Note: in the experiment, I2C communication is used. We need to check the iic address first( enter command：i2cdetect -y 1 and press“Enter”. If failed, check the wiring is correct or not. If correct, you need to enable I2C communication function of Raspberry Pi, project 19 is for your reference.
After enabling the I2C communication，input the following commands and press “Enter”.
cd /home/pi/pythonCode_A
python 23_water_buzzer.py
Test Result：
Buzzer makes a sound when water covering the exposed detection part.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
import RPi.GPIO as GPIO
import smbus
import time
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
buz = 18
GPIO.setup(buz,GPIO.OUT)
address = 0x48 ###address ---> device address
cmd = 0x40 ###DA converter command
A0 = 0x40 ###A0 ----> port address
A1 = 0x41
A2 = 0x42
A3 = 0x43
bus = smbus.SMBus(1) ###start the bus
def analogRead(count): ##function,read analog data
read_val = bus.read_byte_data(address,cmd+count)
return read_val
while True: ###loop
value = analogRead(0) ###read A0 data
if(value>30):
GPIO.output(buz,GPIO.HIGH)
else:
GPIO.output(buz,GPIO.LOW)
print("data:%1.0f" %(value)) ###print data
time.sleep(0.05) ###delay 0.05 second
GPIO.cleanup()
Project 24：5V Relay + Water Pump
Description：
From a safety perspective, we specially designed this relay module with NO (normally open) and NC (normally closed) terminals. In this lesson, we will learn a special and easy-to-use switch, which is the relay module. Use the relay to start the motor.
In daily life, the electronic device is driven by 220V AC and controlled by switch. People will be in danger once the electricity leakage happens, connecting switch to 220V AC directly.
Therefore, we design a relay module with NO and NC ends. Let’s get started.
Components：
|
|
|
|
|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40pin Colorful Jumper Wires*1 |
Breadboard*1 |
|
|
|
|
Relay Module*1 |
Water Pipe*1 |
M-F Dupont Line |
220Ω Resistor*1 |
|
|
|
|
Screwdriver*1 |
Jumper Wires |
Water Pump*1 |
Component Knowledge
Relay
It is an “automatic switch” that uses a small current to control the operation of a large current.
Control input voltage: 5V
Rated load: 5A 250VAC (NO/NC) 5A 24VDC (NO/NC)
Water Pump
Working voltage: DC3-5V,
Working current: 100-200mA,
Head: 0.3-0.8 meters,
Flow rate: 1.2-1.6L/min,
Weight: 28 grams
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”.
cd /home/pi/pythonCode_A
python 24_relay.py
Test Result：
Water pump activates when the indication on relay module turns on.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
import RPi.GPIO as GPIO
from time import sleep
relayPin = 18 ##define relay pin
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
GPIO.setup(relayPin,GPIO.OUT)
while True:
GPIO.output(relayPin,GPIO.HIGH) ##Starting relay
print("turn on")
sleep(5)
GPIO.output(relayPin,GPIO.LOW) ##Close relay
print("turn off")
sleep(1)
GPIO.cleanup()
Project 25：Watering Flower Device
Description：
The household plants are popular in many a communities. They will die if you forget to water them, how about making an automatic watering device?
Components：
|
|
|
|
|
|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
Relay Module*1 |
|
|
|
|
|
Water Pump*1 |
Soil Humidity Sensor*1 |
Keyestudio PCF8591 A/D Converter Module*1 |
Screwdriver*1 |
Water Pipe*1 |
|
|
|||
M-F Dupont Line |
Jumper Wires |
Component Knowledge
Soil Humidity Sensor：
This is a simple soil humidity sensor aims to detect the soil humidity.
If the soil is in lack of water, the analog value output by the sensor will decrease; otherwise, it will increase. If you use this sensor to make an automatic watering device, it can detect whether your botany is thirsty to prevent it from withering when you go out.
Using the sensor with controller makes your plant more comfortable and your garden smarter. The soil humidity sensor module is not as complicated as you might think, and if you need to detect the soil in your project, it will be your best choice.
Schematic Diagram：
Run Example Code：
Note: in the experiment, I2C communication is used. We need to check the iic address first( enter command：i2cdetect -y 1 and press“Enter”. If failed, check the wiring is correct or not. If correct, you need to enable I2C communication function of Raspberry Pi, project 19 is for your reference.
After enabling the I2C communication，input the following commands and press “Enter”.
cd /home/pi/pythonCode_A
python 25_soil.py
Test Result：
Water pump starts running when soil humidity sensor detects the drought of soil.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
import RPi.GPIO as GPIO
import smbus
import time
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
pumpPin = 18
GPIO.setup(pumpPin,GPIO.OUT)
address = 0x48 ###address ---> device address
cmd = 0x40 ###DA converter command
A0 = 0x40 ###A0 ----> port address
A1 = 0x41
A2 = 0x42
A3 = 0x43
bus = smbus.SMBus(1) ###start the bus
while True: ###loop
##Vout = 10 ###10*0.0196=0.196V
##bus.write_byte_data(address,cmd,Vout) ###DA converter
bus.write_byte(address,A0) ###which port of the device you want to access
value = bus.read_byte(address) ###access the data
if(value<30): ##When the soil moisture value is less than 50, turn on the relay to start the water pump
GPIO.output(pumpPin,GPIO.HIGH)
else:
GPIO.output(pumpPin,GPIO.LOW)
print("data:%1.0f" %(value)) ###print data
time.sleep(0.5) ###delay 0.5 second
GPIO.cleanup()
Project 26：Servo
Description：
Servo is applied widely, especially for robot like human robots and moving robots. In this lesson, we will learn how it works.
Components：
|
|
|
|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
|
|
|
Breadboard*1 |
Servo Motor*1 |
Jumper Wires |
Component Knowledge
Servo:
A location(angle) driver which can rotate a certain angle with high accuracy. It has three external wires which are brown, red and orange,. Brown one is grounded, red one is positive pole of power and orange one is signal wire.
The rotation angle of servo motor is controlled by regulating the duty cycle of PWM (Pulse-Width Modulation) signal. The standard cycle of PWM signal is 20ms (50Hz). Theoretically, the width is distributed between 1ms-2ms, but in fact, it’s between 0.5ms-2.5ms. The width corresponds the rotation angle from 0° to 180°. But note that for different brand motor, the same signal may have different rotation angle.
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 26_servo.py
Test Result：
Enter the angle value and servo rotates the corresponding value, as shown below:
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
import RPi.GPIO as GPIO
import time
servo_min_angle = 2.5 ##define pulse duty cycle for minimun angle of servo
servo_max_angle = 12.5 ##define pulse duty cycle for maximun angle of servo
servopin = 18 ##servo Pin
GPIO.setmode(GPIO.BCM) ##BCM numbers
GPIO.setup(servopin,GPIO.OUT)
p = GPIO.PWM(servopin,50) ##set 50Hz , The working frequency of the steering gear is 50Hz
p.start(0) ## start PWM
time.sleep(2)
##define function, map a value from one range to another range
def map(angle, val1, val2, min_angle, max_angle):
return (max_angle-min_angle)*(angle-val1)/(val2-val1)+min_angle
while(True): ##loop
p.ChangeDutyCycle(0) ##set
time.sleep(0.4)
b = input("input Angle:")
b = int(b)
c = map(b, 0, 180, servo_min_angle, servo_max_angle) ##map angle from 0~180 to 2.5~12.5
p.ChangeDutyCycle(c)
time.sleep(0.4)
p.stop()
GPIO.cleanup()
Project 27：L293D Driver Motor
Description：
In generally, we use a DC motor to make smart car. What should we do if we want to control the rotation speed and direction? Here, we need an L293D driver motor.
Components:
|
|
|
|
|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful jumper Wires*1 |
Breadboard*1 |
|
|
|
|
L293D Chip*1 |
Fan |
Motor*1 |
Jumper Wires |
Component Knowledge:
L293D Chip:
It is a DC current DC IC which is applied to drive DC motor and stepper motor. In addition, it has 16 pins driving two-way DC motor at same time.
Input voltage range: 4.5 V ~ 36 V
Output current: MAX 600mA, can drive inductive loaded, especially its input end can be connected to MCU directly, controlled by MCU easily.
The two-channel motor can be driven and rotate clockwise and anticlockwise when changing the high and low level on input port.
## |
Pin Name |
Description |
|---|---|---|
1 |
Enable1 |
Enable pin input 1(2) and Input 2(7) |
2 |
In1 |
Control output1 and controlled by digital circuit |
3 |
Out1 |
Connect one end of motor1 |
4 |
0V |
Connected to 0V of circuit. |
5 |
0V |
Connected to 0V of circuit. |
6 |
Out2 |
Connect the other end of motor1 |
7 |
In2 |
Control output2 and controlled by digital circuit |
8 |
+V motor |
Connect to 4.5V-36V) of motor |
9 |
Enable2 |
Enable pin input 3(10) and 4(15) |
10 |
In3 |
Control output pin 3 |
11 |
Out3 |
Connect one end of motor 2 |
12 |
0V |
Connected to 0V of circuit. |
13 |
0V |
Connected to 0V of circuit. |
14 |
Out4 |
Connect the other end of motor 2 |
15 |
In4 |
Control output 4 and controlled by digital circuit |
16 |
+V |
Connect to + 5V to enable IC function |
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 27_L293D_motor.py
Test Result：
Motor rotates clockwise for 3s, stops for 2s, anticlockwise for 3s and stops for 2 s.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
import RPi.GPIO as GPIO
import time
##define L293D pin
INA1 = 17
INA2 = 27
ENA = 22
GPIO.setmode(GPIO.BCM)
GPIO.setup(INA1,GPIO.OUT)
GPIO.setup(INA2,GPIO.OUT)
GPIO.setup(ENA,GPIO.OUT)
pwmA = GPIO.PWM(ENA,100) ##create a PWM instance
pwmA.start(0) ##start PWM
def forward():
GPIO.output(INA1,GPIO.HIGH)
GPIO.output(INA2,GPIO.LOW)
pwmA.ChangeDutyCycle(100)
def back():
GPIO.output(INA1,GPIO.LOW)
GPIO.output(INA2,GPIO.HIGH)
pwmA.ChangeDutyCycle(70)
def stop():
pwmA.ChangeDutyCycle(0)
while True: ##loop
forward()
time.sleep(3)
stop()
time.sleep(2)
back()
time.sleep(3)
stop()
time.sleep(2)
pwmA.stop() ##stop PWM
GPIO.cleanup() ##release all GPIO
Project 28：Ultrasonic
Description：
An ultrasonic sensor is an electronic device that measures the distance of a target object by emitting ultrasonic sound waves, and converts the reflected sound into an electrical signal.
Components：
|
|
|
|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
|
|
|
Breadboard*1 |
HC-SR04 Ultrasonic Sensor*1 |
Jumper Wires |
Component Knowledge
The ultrasonic module will emit the ultrasonic waves after trigger signal. When the ultrasonic waves encounter the object and are reflected back, the module outputs an echo signal, so it can determine the distance of object from the time difference between trigger signal and echo signal.
The t is the time that emitting signal meets obstacle and returns.
and the propagation speed of sound in the air is about 343m/s, therefore, distance = speed * time, because the ultrasonic wave emits and comes back, which is 2 times of distance, so it needs to be divided by 2, the distance measured by ultrasonic wave = (speed * time)/2
Use method and timing chart of ultrasonic module:
Setting the delay time of Trig pin of SR04 to 10μs at least, which can trigger it to detect distance.
After triggering, the module will automatically send eight 40KHz ultrasonic pulses and detect whether there is a signal return. This step will be completed automatically by the module.
If the signal returns, the Echo pin will output a high level, and the duration of the high level is the time from the transmission of the ultrasonic wave to the return.
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”
cd /home/pi/pythonCode_A
python 28_ultrasonic.py
Test Result：
Terminal prints the detected distance, unit is cm.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
import RPi.GPIO as GPIO
import time
GPIO.setmode(GPIO.BCM)
##define GPIO pin
GPIO_TRIGGER = 23
GPIO_ECHO = 24
##set GPIO mode (IN / OUT)
GPIO.setup(GPIO_TRIGGER, GPIO.OUT)
GPIO.setup(GPIO_ECHO, GPIO.IN)
def distance():
## 10us is the trigger signal
GPIO.output(GPIO_TRIGGER, True)
time.sleep(0.00001) ##10us
GPIO.output(GPIO_TRIGGER, False)
start_time = time.time()
stop_time = time.time()
while GPIO.input(GPIO_ECHO) == 0: ##Indicates that the ultrasonic wave has been emitted
start_time = time.time() ##Record launch time
while GPIO.input(GPIO_ECHO) == 1: ##Indicates that the returned ultrasound has been received
stop_time = time.time() ##Record receiving time
time_elapsed = stop_time - start_time ##Time difference from transmit to receive
distance = (time_elapsed * 34300) / 2 ##Calculate the distance
return distance ##Return to calculated distance
if __name__ == '__main__': ##Program entry
try:
while True:
dist = distance() ##
print("Measured Distance = {:.2f} cm".format(dist)) ##{:.2f},Keep two decimal places
time.sleep(0.1)
## Reset by pressing CTRL + C
except KeyboardInterrupt:
print("Measurement stopped by User")
GPIO.cleanup()