Lesson 10 Slide Switch¶
Introduction¶
In this lesson, we will learn how to use a Slide Switch. Usually, the slide switch is soldered on PCB as a power switch, but here we need to insert it into the breadboard, thus it may not be tightened. And we use it on the breadboard is to show its function.
Components¶
- 1 * Raspberry Pi
- 1 * T-Extension Board
- 1 * 40-Pin GPIO Cable
- 1 * Breadboard
- 1 * Slide Switch
- 2 * LED
- 3 * Resistors (220Ω,10kΩ)
- 1 * USB cable
- Jumper wires
- 1 * 104 Capacitor Ceramic
Principle¶
Slide Switch
A slide switch, just as its name implies, is to slide the switch bar to connect or break the circuit, and further switch circuits. The common-used types are SPDT, SPTT, DPDT, DPTT etc. The Slide Switch is commonly used in low-voltage circuit. It features flexibility and stability, and widely applies in electric instruments and electric toys.
How it works: Use the middle pin as the fixed one. When you pull the slide to the left, the left two pins are connected; to the right, the right two pins connected. Thus, it connects and disconnects circuits as a switch. See the figure below:
The circuit symbol of the slide switch is as shown below. 2 in the figure means the middle pin.
Principle: Connect the middle pin of the Slide Switch to B17, and two LEDs to pin B18 and B27 respectively. Then when you pull the slide, you can see the two LEDs light up alternately.
Experimental Procedures¶
Step 1: Build the circuit.
For C Language Users:¶
Step 2: Go to the folder of the code.
cd /home/pi/SunFounder_Super_Kit_V3.0_for_Raspberry_Pi/C
Step 3: Compile.
make 10_slideSwitch
Step 4: Run the executable file above.
sudo ./10_slideSwitch
Note
If it does not work after running, or there is an error prompt: “wiringPi.h: No such file or directory”, please refer to C code is not working?.
Code
#include <wiringPi.h>
#include <stdio.h>
#define slidePin 0
#define led1 1
#define led2 2
int main(void)
{
// When initialize wiring failed, print messageto screen
if(wiringPiSetup() == -1){
printf("setup wiringPi failed !");
return 1;
}
pinMode(slidePin, INPUT);
pinMode(led1, OUTPUT);
pinMode(led2, OUTPUT);
printf("\n");
printf("\n");
printf("========================================\n");
printf("| Slide Switch |\n");
printf("| ------------------------------ |\n");
printf("| Middle pin of slide switch |\n");
printf("| connect to gpio0； |\n");
printf("| |\n");
printf("|slide switch to contral which led on. |\n");
printf("| |\n");
printf("| SunFounder|\n");
printf("========================================");
printf("\n");
printf("\n");
while(1){
// slide switch high, led1 on
if(digitalRead(slidePin) == 1){
digitalWrite(led1, LOW);
digitalWrite(led2, HIGH);
printf("LED1 on\n");
delay(100);
}
// slide switch low, led2 on
if(digitalRead(slidePin) == 0){
digitalWrite(led2, LOW);
digitalWrite(led1, HIGH);
printf(".....LED2 on\n");
delay(100);
}
}
return 0;
}
Code Explanation
/* When the slide is pulled to the left, the middle pin and left one are
connected; the Raspberry Pi reads a high level at the middle pin, so the
LED1 is on and LED2 off */
if(digitalRead(slidePin) == 1)
{
digitalWrite(led1, LOW);
digitalWrite(led2, HIGH);
printf("LED1 on\n");
delay(100);
}
/* When the slide is pulled to the right, the middle pin and right one
are connected; the Raspberry Pi reads a low, so the LED2 is on and LED1
off */
if(digitalRead(slidePin) == 0)
{
digitalWrite(led2, LOW);
digitalWrite(led1, HIGH);
printf(".....LED2 on\n");
delay(100);
}
For Python Users:¶
Step 2: Get into the folder of the code.
cd /home/pi/SunFounder_Super_Kit_V3.0_for_Raspberry_Pi/Python
Step 3: Run.
sudo python3 10_slideSwitch.py
Code
import RPi.GPIO as GPIO
import time
from sys import version_info
if version_info.major == 3:
raw_input = input
# Set #17 as slide switch pin, #18 as led1 pin, #27 as led2 pin
slidePin = 17
led1Pin = 18
led2Pin = 27
# Define a function to print message at the beginning
def print_message():
print ("========================================")
print ("| Slide Switch |")
print ("| ------------------------------ |")
print ("| Middle pin of slide switch |")
print ("| connect to gpio17; |")
print ("| |")
print ("|slide switch to contral which led on. |")
print ("| |")
print ("| SunFounder|")
print ("========================================\n")
print ("Program is running...")
print ("Please press Ctrl+C to end the program...")
#raw_input ("Press Enter to begin\n")
# Define a setup function for some setup
def setup():
# Set the GPIO modes to BCM Numbering
GPIO.setmode(GPIO.BCM)
# Set slidePin input
# Set ledPin output,
# and initial level to High(3.3v)
GPIO.setup(slidePin, GPIO.IN)
GPIO.setup(led1Pin, GPIO.OUT, initial=GPIO.HIGH)
GPIO.setup(led2Pin, GPIO.OUT, initial=GPIO.HIGH)
# Define a main function for main process
def main():
# Print messages
print_message()
while True:
# slide switch high, led1 on
if GPIO.input(slidePin) == 1:
print (" LED1 ON ")
GPIO.output(led1Pin, GPIO.LOW)
GPIO.output(led2Pin, GPIO.HIGH)
# slide switch low, led2 on
if GPIO.input(slidePin) == 0:
print (" LED2 ON ")
GPIO.output(led2Pin, GPIO.LOW)
GPIO.output(led1Pin, GPIO.HIGH)
time.sleep(0.5)
# Define a destroy function for clean up everything after
# the script finished
def destroy():
# Turn off LED
GPIO.output(led1Pin, GPIO.HIGH)
GPIO.output(led2Pin, GPIO.HIGH)
# Release resource
GPIO.cleanup()
# If run this script directly, do:
if __name__ == '__main__':
setup()
try:
main()
# When 'Ctrl+C' is pressed, the child program
# destroy() will be executed.
except KeyboardInterrupt:
destroy()
Code Explanation
'''When the slide is pulled to the left, the middle pin and left one are
connected; the Raspberry Pi reads a high level at the middle pin, so the
LED1 is on and LED2 off. '''
if GPIO.input(slidePin) == 1:
print (" LED1 ON ")
GPIO.output(led1Pin, GPIO.LOW)
GPIO.output(led2Pin, GPIO.HIGH)
'''When the slide is pulled to the right, the middle pin and right one are
connected; the Raspberry Pi reads a low, so the LED2 is on and LED1 off.'''
if GPIO.input(slidePin) == 0:
print (" LED2 ON ")
GPIO.output(led2Pin, GPIO.LOW)
GPIO.output(led1Pin, GPIO.HIGH)
Now pull the slide, and you can see the two LEDs light up alternately.
