Kushal Das

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Building IoT enabled power-strip with MicroPython and NodeMCU

This was on my TODO list for a long time. But, never managed to time to start working on it, I was also kind of scared of doing the AC wiring without adult supervision :).

Items used

  • Power-strip
  • USB power plug (any standard mobile phone charger)
  • wires
  • NodeMCU Amica
  • Relay board
  • MicroPython
  • Mosquitto server on my home network

I ordered double relay boards (this one was marked for Arduino) from Amazon, and they were laying in the boxes in the Pune Hackerspace for a long time.

Yesterday, we had a Raspberry Pi workshop in the hackerspace as part of the Python Pune monthly meetup. Nikhil was present in the meetup, and I asked for help from him as he is a real hardware expert.

We took one of the existing power-strip from the hackerspace, and also a mobile phone charger. After taking out 2 of the power sockets we had enough space to plug-in the rest of the system inside of it. Of course, Nikhil did all the hard work of soldering the wires in the proper manner.

The relay board is connected to a NodeMCU Amica running MicroPython. It has a code like the following example:

import time
from machine import Pin
from umqtt.simple import MQTTClient

# Received messages from subscriptions will be delivered to this callback
def sub_cb(topic, msg):
    led1 = Pin(14,Pin.OUT)
    if msg == b"on_msg":
        led1.low()
    elif msg == b"off_msg":
        led1.high()

def main(server="SERVER_IP"):
    c = MQTTClient("umqtt_client", server)
    c.set_callback(sub_cb)
    c.connect()
    c.subscribe(b"your_topic")
    while True:
        c.wait_msg()
    c.disconnect()

if __name__ == "__main__":
    try:
        time.sleep(10)
        main()
    except:
        pass

I will have to cover up the holes with something, and also push the code to a proper repository. Meanwhile this was the first usable thing I made with help from friends in the Hackerspace Pune. Come and join us to have more fun and build new things.

Btw, remember to have a password protected mosquitto server :)

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