Writing threads into code for 4 channel relay on pi

Hi Clem,

You're right, no need to separate it. I just did it to make it look like a timer ISR (the tick function) and the main code. With a microcontroller I would have separated it, so the ISR is never hung for a long time, so I just repeated with the Python code, i.e. the tick will always execute fast, whereas the main code can be slow if desired. In the OP use-case there's no need for that as you say.

setting up another pi so i can play with some codes. i think i will start with yours shabaz. i actually have an old laptop somewhere with ubuntu on it also, maybe ill dig it out and update and use it for practice.

I guess my question is whether the threads have to be aware of each other at all for any reason? if not, it isn't too bad. Coordinating communication between threads on the other hand is a total nightmare

Here's a working little ditty using threading.  Just change the "print" commands to a command for however you are switching the relays:

import threading, time

def relay1():
        while (True):
                print("Relay 1 on!\n")
                time.sleep(3)
                print("Relay 1 off!\n")
                time.sleep(5)

def relay2():
        print("Relay 2 on!\n")
        time.sleep(300) #(5 x 60 =300 seconds)
        print("Relay 2 off!\n")

# main execution
relay1_thread=threading.Thread(target=relay1)
relay2_thread=threading.Thread(target=relay2)

relay1_thread.start()
relay2_thread.start()
print("Relay 3 On!")
print("Relay 4 On!")

Reference:  https://docs.python.org/3/library/threading.html

See ya',

Sean

Check with...Python Multithreading

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

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!