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Writing threads into code for 4 channel relay on pi

john2674

Hi i am a super noob at all things PI, i have done a few simple projects. That said coding is really new to me. Ive read python for dummies and quite a few articles on the web so far, but my latest project im stuck.

Im trying to write a code to controll a 4 channel relay board with my pi. But i want my relays to turn off and on at different intervals independant of each other. So far i think i need to use threading commands, but im not sure how to write them? As an example of what im trying to accomplish.

Relay 1 on 3 seconds off 5 seconds repeating forever

Relay 2 on 5 minutes then off permanently

Relay 3 on permanently

Relay 4 on permanently

 

If anybody can point me in a direction where i can learn these code commands i will be super grateful!

Ive tried searching all over and cant find what i need. Im sure i just need to get better at searching though lol.

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  • 0

    Hi

    You're on the right track with threading! Since each relay operates independently, using threads will allow them to run at different intervals without blocking each other.

    Here’s a simple Python script to control your 4-channel relay board using a Raspberry Pi and the GPIO library:

    Steps to Follow:

    1. Install RPi.GPIO if not already installed:

      bash
      CopyEdit
      pip install RPi.GPIO

    2. Connect your relay board to the Raspberry Pi GPIO pins.

    3. Use threading to handle different relay timings.

    Python Code for Relay Control

    python
     
    import RPi.GPIO as GPIO import time import threading # Pin definitions (adjust based on your setup) RELAY_1 = 17 # GPIO pin numbers RELAY_2 = 27 RELAY_3 = 22 RELAY_4 = 23 # GPIO setup GPIO.setmode(GPIO.BCM) GPIO.setup([RELAY_1, RELAY_2, RELAY_3, RELAY_4], GPIO.OUT, initial=GPIO.LOW) # Function for Relay 1 (on 3s, off 5s forever) def relay_1_control(): while True: GPIO.output(RELAY_1, GPIO.HIGH) time.sleep(3) GPIO.output(RELAY_1, GPIO.LOW) time.sleep(5) # Function for Relay 2 (on 5 minutes, then off permanently) def relay_2_control(): GPIO.output(RELAY_2, GPIO.HIGH) time.sleep(300) # 5 minutes GPIO.output(RELAY_2, GPIO.LOW) # Function for Relay 3 (always on) def relay_3_control(): GPIO.output(RELAY_3, GPIO.HIGH) # Function for Relay 4 (always on) def relay_4_control(): GPIO.output(RELAY_4, GPIO.HIGH) # Create and start threads thread_1 = threading.Thread(target=relay_1_control) thread_2 = threading.Thread(target=relay_2_control) thread_1.start() thread_2.start() # Run Relay 3 & 4 directly (since they stay ON) relay_3_control() relay_4_control() # Keep the main thread running to prevent exit try: while True: time.sleep(1) except KeyboardInterrupt: GPIO.cleanup() # Clean up GPIO on exit print("GPIO Cleanup Done!")

    Explanation of the Code:

    • Relay 1 cycles every 3s ON / 5s OFF using a loop in a thread.

    • Relay 2 turns ON for 5 minutes, then OFF permanently.

    • Relay 3 & 4 stay ON permanently.

    • Threads allow independent timing for each relay.

    • GPIO.cleanup() ensures safe shutdown when stopping the script.

    Next Steps:

    • If you need more advanced control, look into asyncio or multi-threading queues.

    • Try adding a button or web interface to control the relays interactively.

    Let me know if you need any modifications!

Reply
  • 0

    Hi

    You're on the right track with threading! Since each relay operates independently, using threads will allow them to run at different intervals without blocking each other.

    Here’s a simple Python script to control your 4-channel relay board using a Raspberry Pi and the GPIO library:

    Steps to Follow:

    1. Install RPi.GPIO if not already installed:

      bash
      CopyEdit
      pip install RPi.GPIO

    2. Connect your relay board to the Raspberry Pi GPIO pins.

    3. Use threading to handle different relay timings.

    Python Code for Relay Control

    python
     
    import RPi.GPIO as GPIO import time import threading # Pin definitions (adjust based on your setup) RELAY_1 = 17 # GPIO pin numbers RELAY_2 = 27 RELAY_3 = 22 RELAY_4 = 23 # GPIO setup GPIO.setmode(GPIO.BCM) GPIO.setup([RELAY_1, RELAY_2, RELAY_3, RELAY_4], GPIO.OUT, initial=GPIO.LOW) # Function for Relay 1 (on 3s, off 5s forever) def relay_1_control(): while True: GPIO.output(RELAY_1, GPIO.HIGH) time.sleep(3) GPIO.output(RELAY_1, GPIO.LOW) time.sleep(5) # Function for Relay 2 (on 5 minutes, then off permanently) def relay_2_control(): GPIO.output(RELAY_2, GPIO.HIGH) time.sleep(300) # 5 minutes GPIO.output(RELAY_2, GPIO.LOW) # Function for Relay 3 (always on) def relay_3_control(): GPIO.output(RELAY_3, GPIO.HIGH) # Function for Relay 4 (always on) def relay_4_control(): GPIO.output(RELAY_4, GPIO.HIGH) # Create and start threads thread_1 = threading.Thread(target=relay_1_control) thread_2 = threading.Thread(target=relay_2_control) thread_1.start() thread_2.start() # Run Relay 3 & 4 directly (since they stay ON) relay_3_control() relay_4_control() # Keep the main thread running to prevent exit try: while True: time.sleep(1) except KeyboardInterrupt: GPIO.cleanup() # Clean up GPIO on exit print("GPIO Cleanup Done!")

    Explanation of the Code:

    • Relay 1 cycles every 3s ON / 5s OFF using a loop in a thread.

    • Relay 2 turns ON for 5 minutes, then OFF permanently.

    • Relay 3 & 4 stay ON permanently.

    • Threads allow independent timing for each relay.

    • GPIO.cleanup() ensures safe shutdown when stopping the script.

    Next Steps:

    • If you need more advanced control, look into asyncio or multi-threading queues.

    • Try adding a button or web interface to control the relays interactively.

    Let me know if you need any modifications!

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