IN-14 Nixie Clock – Concrete Design | Optional ESP32 & Home Assistant Integration

A combination of vintage Nixie technology, modern electronics and minimalist concrete design.

This project features six genuine IN-14 Nixie tubes inside a custom-designed concrete housing with cork details.

My goal was to combine the warm orange glow of vintage Nixie tubes with the clean, industrial appearance of concrete.

The housing is produced using 3D-printed molds, allowing you to create your own concrete clock.

The clock works as a standalone device, but it can also be upgraded with an ESP32-C3 for Wi-Fi connectivity and optional Home Assistant integration.

Features

• 6 genuine IN-14 Nixie tubes

• Custom concrete housing

• 3D-printable concrete casting molds

• Minimalist industrial design

• Cork details

• Brass threaded inserts for feet and control knobs

• Relocated physical control buttons

• 12/24-hour time display

• Adjustable cathode anti-poisoning cycle

• RGB tube backlighting

• Optional ESP32-C3 and Home Assistant integration

• Optional automatic configuration using two relays

Required Components

Nixie Clock Electronics

6× IN-14 Nixie Tubes

The six Nixie tubes must be purchased separately. They are not included with the controller PCB.

I purchased mine on eBay.

Make sure the tubes are tested, functional and compatible with the controller.

Find IN-14 Nixie Tubes on eBay

1× STM8S005 IN-14 Clock Controller PCB – 12 V Version

The controller board operates the six Nixie tubes and includes the necessary high-voltage circuit, clock functions and RGB backlighting.

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1× 12 V DC Power Supply

A suitable 12 V DC power supply is required.

Make sure the power supply has sufficient capacity for the controller and any additional electronics.

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Housing and Assembly Materials

Concrete Casting Material

Use a fine-grained casting compound suitable for producing detailed concrete objects.

The required amount of concrete and water depends on the final housing and the manufacturer's specified mixing ratio.

Self-Adhesive Cork Strip

Used for the decorative cork details.

Size: 20 mm wide, 3 mm thick.

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Brass Threaded Inserts

Size: M6 × 12.5 mm × OD10 mm

These inserts are used to attach the feet and control knobs.

Select the correct size when ordering.

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Super Glue (Cyanoacrylate Adhesive)

Super glue is required for:

• Bonding certain 3D-printed mold components together.

• Securing the brass threaded inserts in their designated 3D-printed components.

Additional Materials

• Suitable mounting screws

• Brass Threaded Inserts M3

• Electrical wires

• Electrical insulation

• Appropriate electrical connectors

• Suitable external momentary push-buttons or the original relocated buttons

Optional ESP32 Smart Home Upgrade

The Nixie clock works without any ESP32 or Home Assistant integration.

However, I decided to add an ESP32-C3 to make the clock more flexible and enable smart-home control.

The ESP32 can switch the clock's power supply and automatically operate the original control buttons.

Additional Electronics

1× ESP32-C3 Super Mini

Provides Wi-Fi connectivity and controls the MOSFET and relay modules.

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1× Mini360 DC-DC Step-Down Converter

Converts the 12 V power supply to 5 V for the ESP32.

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1× MOSFET Switching Module

Used to control the 12 V power supply to the Nixie clock.

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2× 3.3 V Relay Modules with Optocouplers

Used to electronically simulate the UP and DOWN button presses.

The relays are connected in parallel with the corresponding physical buttons.

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Preparing the 3D-Printed Concrete Mold

The concrete housing is produced using several 3D-printed components.

Some of these components must be permanently joined with super glue before the concrete is poured.

Mold Preparation

• Print all required mold components.

• Test-fit the individual parts before gluing.

• Apply super glue to the required contact surfaces.

• Press the parts together and allow the adhesive to cure.

Make sure all glued joints have cured before filling the mold with concrete.

Installing the Brass Threaded Inserts

The M6 brass threaded inserts are used for mounting the feet and control knobs.

Insert dimensions: M6 × 12.5 mm × OD10 mm

The inserts must be positioned in the designated 3D-printed components and secured using super glue.

1. Check the fit of each insert.

2. Apply a suitable amount of super glue.

3. Insert the brass threaded insert into its designated position.

4. Make sure it is correctly aligned.

5. Allow the adhesive to cure completely.

The inserts in this project are glued into place rather than installed using heat.

Concrete Casting

Once the printed mold parts have been assembled and all glued connections have cured, the concrete housing can be cast.

Casting Instructions

1. Assemble the complete mold.

2. Prepare the casting compound according to the manufacturer's instructions.

3. Carefully pour the concrete into the mold.

4. Gently tap or vibrate the mold to help trapped air escape.

5. Allow the concrete to cure sufficiently.

The exact curing time depends on the casting material.

Do not remove the mold too early, as this may damage the concrete surface or edges.

Concrete Filling Height

When pouring the concrete, make sure to fill the mold only up to the step (ledge) defined in the STL file "Concrete formwork 3".

This step serves as a reference for the correct filling height. Do pour concrete exact this level to ensure the housing has the intended dimensions and shape.

Removing the 3D-Printed Mold

Once the concrete has fully cured, the 3D-printed mold components need to be removed.

For my build, I used heat to soften the printed parts, making them easier to remove without applying excessive force to the concrete.

Heat-assisted mold removal:

• Make sure the concrete has fully cured and is sufficiently dry.

• Heat to approximately 150 °C, depending on the 3D-printing material.

• Do not use a kitchen oven or air fryer that is also used for food preparation.

• Once the plastic has softened, carefully remove the mold components using suitable pliers.

• Allow the concrete housing to cool gradually.

Important safety notes:

• Heated plastics and adhesives can release potentially harmful fumes. Use suitable ventilation.

• Never heat wet or insufficiently cured concrete. Trapped moisture can cause cracking or spalling.

• Wear heat-resistant gloves and eye protection.

Electrical Wiring

The IN-14 controller PCB already contains the electronics required to drive the six Nixie tubes.

You do not need to build the internal high-voltage circuit yourself.

The additional wiring is only required for the power supply, optional ESP32 electronics and relocated buttons.

Basic Version

The standalone clock requires:

• A suitable 12 V DC power supply connected to the clock controller.

• Six compatible IN-14 Nixie tubes.

• Relocated control buttons connected to the appropriate button pads.

Optional ESP32 Version

The additional electronics include:

• A Mini360 converter providing 5 V to the ESP32.

• A MOSFET module switching the clock's 12 V supply.

• Two 3.3 V relay modules connected to GPIO5 and GPIO6.

• Relay contacts wired in parallel with the UP and DOWN buttons.

Refer to the included wiring diagram for the external connections.

Check the actual terminal assignments of your MOSFET and relay modules before connecting them. Similar-looking modules may have different internal circuits.

Before powering the ESP32, adjust and measure the Mini360 output to confirm that it provides 5.0 V.

Relocating the Original Control Buttons

Important: The original control buttons on the Nixie controller PCB need to be relocated for this housing design.

The controller board has physical buttons for adjusting the clock.

For my design, these buttons are removed from their original positions and installed elsewhere in the housing.

Button Modification

1. Carefully desolder the original buttons from the controller PCB.

2. Solder two wires to the corresponding button pads.

3. Extend the wires to the new button positions.

4. Secure the buttons in their designated mounting positions.

Connecting the Optional Relays

If you are using the ESP32 upgrade, the relay contacts are connected in parallel with the UP and DOWN buttons.

Relay 1:

• COM and NO connected across the DOWN button contacts.

Relay 2:

• COM and NO connected across the UP button contacts.

The NC relay contacts are not used.

This allows the buttons to remain manually usable while also allowing the ESP32 to simulate button presses.

IMPORTANT – Adjust the Mini360 Before Connecting the ESP32!

WARNING: An incorrectly adjusted Mini360 step-down converter can permanently damage your ESP32-C3!

The Mini360 is an adjustable DC-DC voltage converter. Its output voltage is not necessarily set to 5 V when delivered.

You MUST adjust and verify the output voltage with a multimeter before connecting the ESP32-C3.

1. Connect the 12 V DC power supply to the Mini360 input terminals (IN+ and IN−).

2. Do NOT connect the ESP32 or any other electronics to the Mini360 output yet.

3. Set your multimeter to DC voltage measurement.

4. Measure the voltage between OUT+ and OUT−.

5. Carefully turn the adjustment potentiometer until the multimeter reads 5.00 V DC.

6. Disconnect the 12 V power supply.

7. Reconnect power and verify that the output is still approximately 5.0 V.

8. Disconnect power again before connecting OUT+ to the ESP32's 5V/VIN pin and OUT− to GND.

Never connect the Mini360 output to the ESP32's 3.3V pin!

Check the polarity and output voltage one final time before powering the complete circuit.

If the voltage cannot be adjusted reliably to 5 V, do not use the converter.

Why Are Two Relays Needed?

Some settings on the clock controller are reset when its power supply is completely disconnected.

I added two relays to automatically restore my preferred settings after each startup.

Relay 1 – DOWN Button

The DOWN button controls the RGB backlighting.

The relay can automatically disable the RGB LEDs beneath the Nixie tubes.

Button sequence used in my build:

1. Press DOWN four times.

2. Wait approximately 3.5 seconds.

3. Press DOWN once more.

Relay 2 – UP Button

The UP button is used to configure the cathode anti-poisoning interval.

The anti-poisoning function periodically cycles through the numbers from 0 to 9 to help prevent uneven cathode wear.

I prefer a nine-minute interval instead of the default one-minute setting.

Button sequence used in my build:

1. Hold UP for approximately three seconds.

2. Press UP eight times.

These sequences are specific to the clock controller firmware used in my build. Other versions may require different timing or button sequences.

ESPHome and Home Assistant

I use ESPHome to program the ESP32-C3.

The ESP32 handles the button sequences locally, while Home Assistant can optionally control the clock over Wi-Fi.

You can create an individual ESPHome configuration using the official documentation or an AI assistant such as ChatGPT.

Home Assistant is entirely optional, and everyone can configure their own automations according to their needs.

No particular sensors or schedules are required.

7. Final Assembly

After the concrete has cured completely and the electrical connections have been prepared:

1. Install the six IN-14 Nixie tubes.

2. Attach the feet and control knobs.

3. Install the clock controller in the housing.

4. Mount the relocated control buttons.

5. If using the smart-home version, install the ESP32, MOSFET and relays.

6. Check insulation, clearances and mechanical stability.

7. Verify the electrical connections before powering on the clock.

8. Install the cork details.

Important Safety Information

WARNING – HIGH VOLTAGE

The Nixie clock controller generates approximately 170 V DC internally.

This voltage can cause serious electrical injury.

This project is intended for people with appropriate electrical knowledge and experience.

• Always disconnect the power supply before working on the electronics.

• Capacitors may retain dangerous voltage after the power supply has been removed.

• Never touch exposed high-voltage circuitry.

• Ensure sufficient electrical insulation and mechanical protection.

• Keep the clock away from moisture and conductive objects.

• Use a properly rated and suitable power supply.

• Provide adequate strain relief and ventilation.

• Do not rely on concrete as an electrical insulator.

• Verify the low-voltage button circuits before attaching external relay contacts.

Do not operate the clock with exposed or accessible high-voltage connections.

You are responsible for ensuring that your finished build is electrically and mechanically safe.

Final Notes

This project combines vintage Nixie technology, 3D printing, concrete casting and optional modern smart-home electronics.

The standalone version is suitable for anyone who wants a minimalist Nixie clock without additional programming.

For those who enjoy electronics and home automation, the ESP32-C3 offers many possibilities for customization.

I hope this project inspires you to create your own version.

If you build one, feel free to share photos of your make!

Enjoy building!