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Every piece of old tech has a story. Sometimes, all it takes is a move to a new house, a bit of solder, and an ESP8266 to give that old hardware a completely new lease on life. This is the story of how a cheap, local-store remote calling bell evolved into a custom, web-controlled smart assistant.

The Backstory: Solving the Load-Shedding Dilemma

It all started in our previous home—a multi-storied apartment complex with two units per floor. The original calling bell switch sat outside our main gate, but its wiring was completely packed tightly inside the walls. There was absolutely no room to fish a new wire through the conduit to connect the switch to our home IPS (Inverter/Backup Power). When the power went out during load shedding, guests couldn't ring the bell.

To solve this without tearing up the walls, I bought a basic wireless calling bell from a local store. The remote transmitter unit was tiny and ran on a long-lasting 12V battery. I hacked it by soldering extension wires directly to its internal button contacts, tucked the tiny transmitter inside the housing of the outside wall switch, and wired it up.

Because the ground floor main collapsible gate still used the house’s original wired bell, this setup gave us an unexpected bonus: we could finally distinguish whether a visitor was down at the ground floor or standing right outside our apartment door.

The Move and the Pivot to IoT

After moving to a new house, the remote bell suddenly lost its purpose and sat idle. But instead of letting it gather dust, I started wondering: Could I convert this into an IoT device to serve as an in-house assistance notifier?

I opened up the receiver unit and began tracing the circuits. By probing the board, I discovered three specific low-voltage trigger points that controlled the device's functions:

Trigger 1: Rings the bell.
Trigger 2: Adjusts the volume.
Trigger 3: Cycles through the default music tracks.

Building the Smart Bell Controller

To bring the bell online, I paired it with a Wemos D1 mini micro-controller. I wired the low-voltage pins from the bell's PCB directly to the Wemos and wrote a custom script to handle all three actions via a clean web interface.

But I didn't stop there. Since I was already building a custom controller, I decided to add a little flair. I integrated a 3.5mm female audio jack acting as a switchable DC power port for a fairy light strip. I attached a 3.5mm male jack to the fairy lights, wrapped the strip around a small DIY helmet stand (which I had previously built out of leftover PVC boards), and hooked it up.

To clean up the presentation, I mounted the entire calling bell assembly to the back panel of the helmet stand. For power, I added a neat female micro-USB port to keep the entire system running seamlessly off a standard 5V mobile charger.

The Result

What started as a simple workaround for apartment load-shedding is now a fully integrated web-controlled notification station. The entire setup is mounted neatly behind the DIY helmet stand, keeping the bedroom looking clean while bringing old hardware into the smart era.

Human, I've opened the drawer, no FOOD! I'll press the RED BUTTON NOW!

As a physical override, we also have a multi-button remote switch unit sitting right in front of the bed (as seen in the right bottom corner of the image next to our cat). Out of its 7 buttons, we configured the prominent red button to instantly ring the bell, giving us a quick, tactile way to call for assistance without needing to pull up the web interface on a phone. With a quick tap on the physical red switch or a click on a laptop, anyone can ring the bell, change the chime, or turn the decorative fairy lights on and off.

Before you throw out your old hardware, open it up—you never know what kind of smart device is hiding inside!

3a:Tea7,

There is nothing quite like the feeling of turning a regular house appliance into a fully automated smart device. Today, I am excited to share the first version of my DIY IoT Relay Controller and its companion piece: a portable switch designed to solve a very specific winter dilemma.

The Core Build: The Relay Controller v1

The main engine behind this build is a Wemos D1 Mini paired with a 5V relay and an embedded power supply module. To keep everything safe, compact, and organized, I packaged the entire setup inside a durable, empty plastic electronic project box enclosure.

One of the most critical parts of the design process was building in a fail-safe mechanism. I wired the default mode to the Normally Closed (NC) port of the relay. This ensures that if the microcontroller fails, encounters a software bug, or drops power internally, the light stays on and can still be managed normally via a physical wall switch.

For the electrical interfaces, one side of the case exposes a DIN Rail twin connector with four dedicated terminals:

Negative Input/Output
Positive Input
Output: Normally Open (NO)
Output: Normally Closed (NC)

Relay Controller - My First Custom IoT Relay and Switch Deployment

The Control Ecosystem: From Raspberry Pi to Local LAN

On the software side, the Wemos D1 Mini hooks directly into my home network over Wi-Fi and speaks via MQTT protocol.

The backend architecture consists of:

A local Raspberry Pi running a custom IoT solution designed entirely by me.
An MQTT server acting as the message broker.
A central Web endpoint that exposes a visual dashboard.

The application is reachable inside my local area network (LAN) and securely over the internet. To remove daily friction, I built an auto-login system that identifies known MAC or IP addresses on my LAN, providing instantaneous dashboard access without entering passwords every time. From this web dashboard, I can toggle power or activate an "invert mode" toggle in case I choose to swap the wiring to the Normally Open (NO) channel down the road.

Light - My First Custom IoT Relay and Switch Deployment

Solving the "Cold Winter Night" Problem: The Switch Controller

While having full web controls over the internet is fantastic, using a smartphone to turn off the lights right before bed isn't always the fastest user experience. To fix this, I created a second peripheral: a physical Switch Controller.

This companion device features:

Another Wemos D1 Mini module
A tactical microswitch
A 5V lithium battery charger circuit + battery pack
An optional auxiliary light that can be toggled via the web page

Instead of printing a brand new shell, I repurposed a cheap, portable battery-operated light bought from AliExpress, customizing its chassis to hold my smart hardware.

Remote Switch - My First Custom IoT Relay and Switch Deployment

The primary mission of this device is simple: mapping a physical button to trigger the main Relay Controller across the room. Now, instead of arguing over who has to step out into the freezing winter air to turn off the overhead light, the controller sits right on the nightstand. One tap from beneath the comfort of the blankets, and it's lights out!

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