How to start using NodeMCU for WiFi projects (Goodbye Arduino?)

Ah Arduino. You were my first gateway to making tiny electronic widgets that interact with the world. I’ve played with platforms that range from small and simple to expensive and complex like FPGAs, but nothing beats the cost and ease-of-use of Arduinos for making tiny devices you sprinkle around your home. Until now…

See the thing is, WiFi has become as common as electricity in many countries. So I keep finding that I want all my devices to connect to the internet — something that Arduino doesn’t do very well. Especially if you want to talk at a higher level; like with HTTP or MQTT. Plus, getting WiFi-enabled Arduino chips or going with alternative platforms like Electric Imp can get pricey.

So that led me to a family of devices built around the ESP8266 chip. Not only do these tend to be cheaper than Ardunios, they have integrated WiFi! (E.g.: D1 mini NodeMCU).

But I noticed something popular among users of these devices. They don’t use the normal Arduino platform, but instead a different NodeMCU firmware. I looked it up and what I liked about it was that its firmware libraries help you do many complex things you normally want to, easily. E.g., you can make your NodeMCU device a web server, or talk MQTT with just a few lines of code.

So I got a NodeMCU chip for under $3 to play with one weekend. I figured out how to flash the firmware and upload my code to it. The process is slightly different from using an Arduino. So I compiled all my notes, scripts and whatever else I needed into a bare-bones package. I plan to use this as my personal template for starting new NodeMCU projects. Since it might be useful to others too, I posted it to github here:

The broad steps for starting a NodeMCU project are:

  1. Download and build the firmware. I recommend using the Docker option. That way, all you do is download the firmware source code from git, customize it (optional), then use docker to build it.
  2. Flash the firmware. The flash command is also in the link in the previous step. Or check out “” in my nodemcu-skeleton git.
  3. Upload your code using luatool. See “” in my git’s ‘test’ dir for reference.

Although the steps are more ‘manual’ than with Arduino, I actually like it better. I never liked working in the clunky Arduino IDE. I prefer coding in my favorite editor, then uploading to the device via command-line. Working with NodeMCU does come with its own quirks, but they’re not too bad once you get into the groove.

I am still experimenting with these $3 NodeMCU chips, but so far I’m liking it. My first project was a sound monitor to keep an ear on the house while we were away for a few days. This was mainly because my wife was worried about leaks from her new aquarium setup. So first, we placed regular water alarms under the aquariums. The sound monitor measures the sound level continuously and streams the data to the web (via Thingspeak). Then I have a cron job that watches the data stream and emails me if anything looks funny. It’s sensitive enough to detect anything from doorbells, loud conversations and microwave beeps… to water alarms and fire alarms.

I might switch to these NodeMCUs as my go-to device for all my future projects!

Happy hacking 🙂

DIY home automation almost-instant-response WIFI smart switch for < $16 with MQTT

Parts list:

Total: $15.55 ($7.28 if you go with the mini NodeMCU)

WARNING!!! this switch can switch up to 110/240V AC @ 10A. This is more than enough to cook your insides or “stop” your heart and kill you. Do not play with your house mains unless you know what you’re doing and you understand the risks. One mistake and you’re dead. If you’re not sure, close this page. It’s not worth it.

I made this WiFi switch to add an IP camera to the outside of my house, without having to run new power lines to it. The idea was to tap into the 110V AC of an existing outdoor porch light to power my camera. I would then keep the switch to the light ON all the time, to power my camera ON all the time. But I didn’t want my porch light to be on all the time. So, a WiFi smart switch will replace the wall switch to control the light. This was acceptable, since we don’t turn the porch light on/off frequently, and it’s better off scheduled (turn on at night) or automated (turn on when motion detected).

My only constraint was that everything had to fit into an in-wall power conduit or switch box. The largest part was the AC/DC transformer/power supply. I managed to find a 1.25A power supply that is 70 x 39 x 31 mm. As a bonus, you can open its metal case and pack your microcontroller and other electronics inside it:

Open the metal case, pack it in. AC comes in the top. DC goes out the bottom to the Relay, microcontroller and my IP camera.

Open the metal case, pack it in. AC comes in the top. DC goes out the bottom to the Relay, microcontroller and my IP camera.

The input of the power supply is 110/240VAC and the output is 12V DC. My IP Camera uses 12V DC, so it took the raw 12V DC. But the Cactus Micro and the Relay need lower voltage. So I used the DC-DC converter to step down 12V DC to 5V DC.

Closer look at the DC bits

Closer look at the DC bits. The blue board I’m lifting up is the microcontroller that talks over WiFi and switches the relay. USB for scale.

Closer look at my camera

Closer look at my camera

Closed up. Compact enough to fit into a wall conduit/switch box.

Closed up. Compact enough to fit into a wall conduit/switch box.

And that’s the WiFi switch. Wire the switch up like this:

Your WiFi switch controls your light or whatever AC load

Your WiFi switch can now control your light or whatever AC load you want up to 240V 10A

The rest of the magic happens in software. There are 2 parts to the software. 1 part is the code you upload to the Arduino microcontroller. That connects to WiFi, listens for on/off commands and switches the relay. The 2nd part is what sends on/off commands to your smart switch.

Software Part 1:
Let’s set up your MQTT broker first. MQTT is the protocol that we’ll use to send commands to your Smart Switch and switch it on/off almost instantly. You can think of MQTT as an “IoT Twitter”. It lets your switch “subscribe” to a topic. Then something else can “publish” to that topic to turn it on/off. You need a MQTT broker because that’s what passes your messages between publisher and sender.

The easiest way to get a MQTT broker is to sign up for CloudMQTT’s free “Cute Cat” plan: The 4 pieces of info you need after you set it up are:
– Your broker’s hostname or IP address
– Your broker’s port
– Your broker’s user
– Your broker’s password

Software Part 2:
Arduino code. I used a Cactus Micro, which has 2 chips in one package: an Arduino chip and an ESP8266 for WiFi. 1st step is to program the ESP8266 with Espduino. Espduino is an Arduino library that makes it easy to connect to WiFi and talk MQTT.

  1. Set up your Cactus Micro arduino to flash the ESP8266’s firmware — upload this Arduino progrmamer sketch:
  2. Flash the ESP8266 with the “espduino firmware”: Use the NodeMCU Flasher if you’re on Windows and the esptool if you’re on Linux.
  3. Upload the Arduino smartswitch sketch below to your Cactus Micro…

IMPORTANT: Use Arduino IDE version 1.0.6. If you use version 1.0.5 your Cactus Micro will be unstable and randomly crash.

Disclaimer: The code below has a little more than the MQTT on/off stuff. I wanted to also show you how to sync time and also upload data to If you don’t need those, just delete them. I included them because I’ve found them useful in all my projects and they show you how you can upload/download regular HTTP via Espduino. I also included some bulletproofing code that reboots the ESP8266 if it malfunctions.

Replace all the “TODO_…” strings with your own info

Once you have everything set up, you can power your switch and test it using the CloudMQTT “Websocket UI.” The code above subscribes your switch to the “/homebot/switches/MY_SMARTSWITCH/cmd” topic. Send a “1” over MQTT to turn it on. Send a “0” or whatever else to turn it off.

Here is mine in action:

Happy switching!

P.S. If you get stuck or have any questions, email me at

P.P.S Please don’t die being stupid with electricity.