Home IoT Hub Series · 20

[Part 20] The house finally fits on one screen - finishing the 20-slot Home IoT Hub

If you followed all the way to Part 19, this is the system running in your home right now.

• 1 brain: a NodeMCU + OLED + buzzer. Sitting in the middle of the living room, scrolling through all 20 slots four at a time to show you the state of your home.
• 19 sensor nodes: scattered around the house, measuring temperature, humidity, door-open, gas, power, even the weight of the food bowl.
• Wi-Fi: a private network called IoT_Hub_Net that connects every sensor node to the brain.
• Alerts: when there's a gas leak, a fire, an open front door, or a near-empty food bowl, the buzzer sounds and the OLED inverts.
• Automatic control: when someone's in the living room and it's hot, the air conditioner turns itself on.

All 20 slots at a glance

What it looks like on the OLED

The OLED 128×64 screen is split into 4 lines per page, 5 pages in total, and auto-scrolls every 3 seconds. Here's what actually shows up on screen.

What each sensor does and how it's judged

A daily routine: how you actually use this system

Morning, waking up — a quick glance at the OLED.

• Check Outside Temp to decide what to wear
• If Rain is 1, grab an umbrella

Before heading out — a 5-second check.

• Front Door 0, Door Lock 1, Stove 0, Living Light OFF → all clear

While you're out — check the web dashboard (optional).

• You can check anytime that Gas Leak and Fire are still 0
• If Pet Bowl drops below 50, swing by to refill during the dog's walk

Coming home — an automatic welcome.

• Open the door and Front Door flips to 1 and the buzzer chirps briefly (the house letting you know someone came in)
• The living-room PIR detects a person → if it's hot, the air conditioner turns on automatically

Before bed — one last check.

• Front Door 0, Gas Leak 0, Fire 0 → sleep easy
• Glance at Bath Hum to decide the exhaust-fan timer

The web dashboard: a second screen

Connect to the brain's STA IP (e.g. http://192.168.0.50) and all 20 cards show up in a grid. You can take in more at a glance than on the OLED. Alert cards are highlighted in red. It refreshes automatically every 30 seconds.

Your phone can connect too, as long as it's on the same network. Add a shortcut to your home screen and it works like an app.

Ideas for future expansion

Right now it's 20 slots, but the way the system is built, you can add as many more as you like.

Sensors worth adding right away (~$7–20)

Sensors worth a bit more investment (~$20–67)

System upgrades (software)

What you learned in this series

Even someone who used to just copy-paste code picks up these skills by following along through Part 19.

• Using the Arduino IDE: installing libraries, configuring boards, debugging with the serial monitor
• ESP8266 Wi-Fi programming: STA, AP, AP+STA modes, HTTP client/server
• Sensor interfacing: I2C (OLED), OneWire (DS18B20), SPI (MAX6675), UART (MH-Z19B), analog, digital, interrupts
• IoT architecture: a central hub + distributed nodes, REST API communication, a self-hosted AP network
• Troubleshooting: the habit of reading the checkpoints and debugging on your own when something breaks

Once you've got all this down, you can tackle any ESP8266 project floating around the internet on your own.

Closing

One ESP8266, one OLED. A project that started with ~$5.00 in parts became a system that watches over and controls your whole home. The important thing is that this isn't the end. Pick one of the expansion ideas above that appeals to you and write Part 21 yourself. The skeleton is already fully built.

And finally, thank you for following this series. I hope your home got a little smarter.

See you at iothub.co.kr.

Field operating checkpoints: troubleshooting, tips, and FAQ

The node code can look short, but real home installation is affected by placement, power, Wi-Fi quality, and sensor noise. Check these points before letting the node become a decision input for the brain server.

Serial Monitor

After uploading, open Tools → Serial Monitor in the Arduino IDE and set the baud rate to 115200. The following is an example Serial Monitor flow for checking normal operation. This is not a real screenshot. It shows the type of overall slot-update log that can be checked from the central hub Serial Monitor.

[BOOT] Home IoT HUB brain - 20 slot dashboard
[AP] IoT_Hub_Net started, ip=192.168.1.1
[HTTP] /set?no1=24.6&no2=58.2 -> 200 OK
[HTTP] /set?no9=1 -> 200 OK, door=OPEN
[HTTP] /set?no13=742&no14=11 -> 200 OK
[DISPLAY] OLED page refresh: temp/humidity/door/air/power
[STATUS] active_slots=20, stale_slots=0, uptime=03:12:44

• If Connected or connected appears, the Wi-Fi step passed.
• If HTTP 200 or 200 OK appears, the value reached the brain server.
• If the value does not update, check both the slot number in the URL and the sensor wiring.