2.2.4 Reed Switch Module¶
Introduction¶
In this project, we will learn about the reed switch, which is an electrical switch that operates by means of an applied magnetic field.

Schematic Diagram¶
T-Board Name |
physical |
wiringPi |
BCM |
GPIO17 |
Pin 11 |
0 |
17 |
GPIO27 |
Pin 13 |
2 |
27 |
GPIO22 |
Pin 15 |
3 |
22 |


Experimental Procedures¶
Step 1: Build the circuit.

Step 2: Change directory.
cd /home/pi/raphael-kit/python/
Step 3: Run.
sudo python3 2.2.4_ReedSwitch.py
The green LED will light up when the code is run. If a magnet is placed close to the reed switch module, the red LED lights up; take away the magnet and the green LED lights up again.
Code
Note
You can Modify/Reset/Copy/Run/Stop the code below. But before that, you need to go to source code path like raphael-kit/python
. After modifying the code, you can run it directly to see the effect.
#!/usr/bin/env python3
import RPi.GPIO as GPIO
import time
ReedPin = 17
Gpin = 27
Rpin = 22
def setup():
GPIO.setmode(GPIO.BCM) #
GPIO.setup(Gpin, GPIO.OUT) # Set Green Led Pin mode to output
GPIO.setup(Rpin, GPIO.OUT) # Set Red Led Pin mode to output
GPIO.setup(ReedPin, GPIO.IN, pull_up_down=GPIO.PUD_UP) # Set ReedPin's mode is input, and pull up to high level(3.3V)
GPIO.add_event_detect(ReedPin, GPIO.BOTH, callback=detect, bouncetime=200)
def Led(x):
if x == 0:
GPIO.output(Rpin, 1)
GPIO.output(Gpin, 0)
if x == 1:
GPIO.output(Rpin, 0)
GPIO.output(Gpin, 1)
def detect(self):
Led(GPIO.input(ReedPin))
def loop():
while True:
pass
def destroy():
GPIO.output(Gpin, GPIO.HIGH) # Green led on
GPIO.output(Rpin, GPIO.LOW) # Red led off
GPIO.cleanup() # Release resource
if __name__ == '__main__': # Program start from here
setup()
detect()
try:
loop()
except KeyboardInterrupt: # When 'Ctrl+C' is pressed, the child program destroy() will be executed.
destroy()
Code Explanation
ReedPin = 17
Gpin = 27
Rpin = 22
def setup():
GPIO.setmode(GPIO.BCM) #
GPIO.setup(Gpin, GPIO.OUT) # Set Green Led Pin mode to output
GPIO.setup(Rpin, GPIO.OUT) # Set Red Led Pin mode to output
GPIO.setup(ReedPin, GPIO.IN, pull_up_down=GPIO.PUD_UP) # Set ReedPin's mode is input, and pull up to high level(3.3V)
GPIO.add_event_detect(ReedPin, GPIO.BOTH, callback=detect, bouncetime=200)
Set the GPIO modes to BCM Numbering. ReedPin
, Gpin
and Rpin
connects to the GPIO17, GPIO27 and GPIO22.
GPIO.add_event_detect()
is used to add an event that is triggered by a change in the value (level) of ReedPin
, at which point the callback function detect()
is called.
def Led(x):
if x == 0:
GPIO.output(Rpin, 1)
GPIO.output(Gpin, 0)
if x == 1:
GPIO.output(Rpin, 0)
GPIO.output(Gpin, 1)
Define a function Led()
to turn the two LEDs on or off. If x=0
, the red LED lights up; otherwise, the green LED will be lit.
def detect(self):
Led(GPIO.input(ReedPin))
In this callback function, the value of the reed switch is used to control the 2 LEDs.