In this project, we will learn to use a relay. It is one of the commonly used components in automatic control system. When the voltage, current, temperature, pressure, etc., reaches, exceeds or is lower than the predetermined value, the relay will connect or interrupt the circuit, to control and protect the equipment.
In this project, we need the following components.
It’s definitely convenient to buy a whole kit, here’s the link:
ITEMS IN THIS KIT
You can also buy them separately from the links below.
Step 1: Build the circuit.
Step 2: Open the code file.
Step 3: Run.
sudo python3 1.3.3_Relay.py
While the code is running, the LED lights up. In addition, you can hear a ticktock caused by breaking normally close contact and closing normally open contact.
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 # Set GPIO17 as control pin relayPin = 17 # Define a setup function for some setup def setup(): # Set the GPIO modes to BCM Numbering GPIO.setmode(GPIO.BCM) # Set relayPin's mode to output, # and initial level to High(3.3v) GPIO.setup(relayPin, GPIO.OUT, initial=GPIO.HIGH) # Define a main function for main process def main(): while True: print ('Relay open...') # Tick GPIO.output(relayPin, GPIO.LOW) time.sleep(1) print ('...Relay close') # Tock GPIO.output(relayPin, GPIO.HIGH) time.sleep(1) # Define a destroy function for clean up everything after # the script finished def destroy(): # Turn off LED GPIO.output(relayPin, 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()
Set the pins of transistor as low level to let the relay open, LED does not turn on.
wait for 1 second.
Set the pins of the transistor as low level to actuate the relay, LED lights up.