TimeSlice: a Dual 13-Segment Display Clock

I designed a custom 13-segment display to achieve a distinctive look and avoid the unwanted spaces typical in similar displays. While this guide focuses on a numeric display, the design can be modified to support text as well.

In this Instructable, I'll guide you step-by-step through building your dual 13-segment display. This customizable clock utilizes WS2812B addressable LEDs to present the time in a modern and elegant way. An ESP32 WROOM microcontroller handles the operations, automatically synchronizing the time with an NTP server for precise accuracy.

Material

• WS2812B addressable LED strip (26 LEDs needed)
• Acrylic sheets (2.5 mm and 5.0 mm thicknesses)
• 3D printer filament (Black)
• White paper 75 G/M2 (A4 or letter)
• Double-sided tape
• Paper tape
• ESP32 microcontroller (I used WROOM)
• Cables 
• Solder wire
• Solderless wire connector (optional)
• Pin headers (2x40)
• DC Jack
• DC Power Supply (5V)
• Hot glue sticks

Tools

• Soldering iron
• 3D printer
• Laser cutter
• Razor blades
• Wire stripper
• Hot glue gun
• Screwdriver (optional)
• Solder wick (optional)

Acknowledgment

I used the Anderson Student Innovation Labs (ALabs) at the University of Minnesota Minneapolis campus for making the laser-cut parts. 

There are only three parts to be printed and the maximum dimension is 97.0 x 160.5 x 24.25 mm. Here are the parts:

1. Display Base (Black)
2. Display Stand (White or Black; 2 pieces)
3. Display Interconnector (White or Black)

Print Settings

I printed the parts using PLA with 20-30% infill and support enabled (except for the Display Base). The slicing was done with Ultimaker Cura (version 5.3.1) and printed using a Creality CR-6 SE printer.

Also, I adjusted the print speed to 120 mm/s, changed wall ordering to "Outside to Inside," and set the support top and bottom Z distances to 0.4 mm (twice the layer height).

Note: The parts were designed using Autodesk Fusion.

Three parts need to be laser cut:

1. Light Diffuser Base (2.5 mm acrylic)
2. Back Cover Support (5.0 mm acrylic)
3. Back Cover (2.5 mm acrylic)

Laser Cutting Settings

I used the Universal Systems Model PLS6.150D Laser Cutter at Alabs to cut the parts.

For the 2.5 mm acrylic, these settings worked for me:

• Material: continuous cast acrylic
• Material thickness: 3.43 mm
• Vector cutting: +50%

For the 5.0 mm acrylic, these settings worked for me:

• Material: cast acrylic
• Material thickness: 6.81 mm
• Vector cutting: +50%

I have attached screenshots of the full settings I used. All other settings were left as default.

Note: I used leftover acrylic for over 50% of this project. I managed to fit the smaller parts onto the leftovers, purchasing only a new sheet for the back covers. Also, the parts were designed using Autodesk Fusion.

For the diffuser, I found that plain white A4 paper works best. Though I tried other methods, including sanding the top of the acrylic light diffuser base, using paper proved to be the simplest and most effective. Follow these steps for assembly:

• Apply a layer of double-sided tape to both sides of the top of the acrylic light diffuser base.
• Cut an A4 sheet to cover the entire top surface of the acrylic.
• Press down on the sheet to ensure proper adhesion.

Trim the excess edges of the A4 sheet and double-sided tape. For trimming, I recommend using razor blades as they offer more precision than scissors.

⚠️ Important Note ⚠️

After testing the display for a while, I realized that using a thin double-sided table was not the best choice. If you look at the test images and videos, you can see a thin line at the center of all the display segments. The thin line represents the space between the two double-sided tape layers I used to attach the paper diffuser. Hence, I should have used a wider double-sided tape (that covers the entire acrylic light diffuser base) to eliminate this problem.

Position the LED strip segments so that the LEDs fit into the holes at the bottom of the display base. Secure the LEDs in place with paper tape or hot glue. Ensure that the output pins (DO) of one strip segment are connected to the input pins (DIn) of the next segment for proper functionality.

When cutting the LED strips, make sure to cut at the white markings in the middle of the solder pads. For the sections where three strips are not cut but placed sequentially into three holes, allow for a slight bulge at the solder pads to ensure that the LEDs sit directly under the holes (future designs will address this issue).

Cut wires between 25 - 40 mm long and strip about 3 mm of insulation from each end. Consider color-coding the wires to simplify the soldering process and debugging. I used green for data, red for power, and black for ground.

Before soldering, apply solder to all the necessary solder pads. Then, place and press the corresponding wires onto the solder spots.

Note: I used 30 AWG wires for their flexibility and small footprint, but I recommend using thicker gauge flexible wires to avoid potential heating issues.

The LED strips and power supply only need four connections to the microcontroller (though three could suffice): one for the left display data line, one for the right display data line, one for powering the microcontroller, and one for the ground connection.

For initial testing, make these connections on a breadboard. I have included a diagram to illustrate the connections.

Once you have set up the connections, compile and upload the "Display_Initial_Sequence.ino" code to the microcontroller. If everything is correct, all the LEDs should light up sequentially. Do this for both display modules.

If you do not have the ESP32 library set up in the Arduino IDE, follow the instructions on this page:

https://randomnerdtutorials.com/installing-the-esp32-board-in-arduino-ide-windows-instructions/

If all the LEDs work properly, upload the actual Wi-Fi clock code: "Display_Wi-Fi_Time.ino".

The software displays the current hour first for 5 seconds and then the minute for another 5 seconds, with different colors for the hour and minute displays. Ideally, there should be four modules (instead of two) to display the full-time at once, with an additional module for the colons.

Once everything is working as expected, it's time to assemble the display and add the finishing touches.

First, insert the display interconnector and stands into the desired holes along the sides of the display base. Ensure the stands are positioned so that the display remains vertical when placed on a flat surface.

On the back side of the display, where the LEDs are located, glue the back cover supports to the left and right edges of each display module using hot glue. Once the supports are in place, apply hot glue to the top surface of the supports and place the back cover over the glue, ensuring it covers the entire back side of each display module.

Use two solderless wire connectors to join all the power connections together and do the same for the ground connections. Then, using a single cable for each, route these connections back to the microcontroller and power jack.

To secure the microcontroller in place (while allowing easy removal if necessary), cut two pieces from a 2x40 pin header. One piece should be 2x3 and the other 2x2 (though 2x1 would be ideal, it’s harder to cut from the long 2x40 piece). Bridge every two adjacent pins with solder using a soldering iron. This setup allows one leg to connect to the microcontroller, with the other pinhole holding a cable that connects to the microcontroller.

Once all the connections are made, apply hot glue to the bottom of the pin headers (where the solder is) and attach them to your chosen location on the back cover of the display. For a cleaner look, position the microcontroller so it is not visible from the front.

This project has been a rewarding journey that combined 3D printing, laser cutting, soldering, and coding. As a newcomer to laser cutting, this was a fantastic introduction to the technique, and the skills I learned can be applied to future projects.

The finished dual 13-segment display is not just functional, it's a conversation starter! The customizable design and flexibility of the LEDs allow it to seamlessly integrate into any space, adding a touch of modern elegance to your living room, bedroom, or workspace. I've personally enjoyed using it in all these settings, and it consistently draws attention.

I hope this Instructable has empowered you to build your own dual 13-segment display! Whether you're a seasoned maker or just getting started, this project offers a fun and educational experience. Remember, keep experimenting, pushing your creative boundaries, and happy making!

Acknowledgements

A big thanks to the Anderson Student Innovation Labs (ALabs) at the University of Minnesota Minneapolis campus! Their resources and support, particularly with the laser cutting, were instrumental in bringing this project to life.