Ninja Timer ready for action at the Train Yard 317 gym's Ultimate Nina Athlete Association competition.

Big Time

Ever wanted to build an enormous timer using 7-segment displays? Here's a way to do just that using NeoPixel strips for the segments and acrylic diffusers to blend the individual LEDs into seamless light sources.

This guide shows how to build 12" tall digits, each made from a meter of NeoPixels cut into segments and then joined at angles. Each digit is controlled by a single Arduino data pin, so you can make and use as many digits as you like, dependant on power supply and available Arduino pins.

Plus, you'll build rugged buttons for starting and stopping the timer, and control an ear-splitting car horn from your Arduino!

Key Techniques

This guide will cover some techniques that are helpful when building a larger project. Fundamentally, this project is the same as simply using a button to tell an Arduino to light up a NeoPixel and beep a buzzer. But sometimes the details of scaling up your project can be intimidating.

Key techniques include:

• Diffusing groups of individual LEDs to make unified light sources
• Controlling long runs of NeoPixels without introducing signal noise
• Addressing a physical strip of NeoPixels as multiple logical segments
• Providing seperate, integrated power to multiple sub-systems 
• Creating polarized, modular interconnects between parts
• Running robust input wiring over dozens or hundreds of feet

Parts

In addition to the parts listed on the sidebar of this guide, you'll need the following:

• Project box such as this for multiple button controls
• Sprinkler timer cabinet to house the electronics
• 12V car horn
• Cat 5e or Cat 6 (Ethernet) cable long enough for your application, x3 (for the Train Yard 312 gym we used two 50' and one 150' lengths)
• For the course stop button stand (you know, the one you dive for at the end of your run!) you'll need:
• 4' of 3" ABS pipe
• 3" ABS pipe coupler
• 3" ABS closet flange

Materials

Each digit panel is made up of multiple layers of cut acrylic. You'll use opaque acrylic for the body and face layers of the panel, and translucent white acrylic for the segment diffusers.

The included CAD drawings are designed to be cut from 6mm and 3mm (roughly 1/4" and 1/8") cast acrylic, but you can adapt the files as you like for other dimensions and materials.

Each panel is cut from six 16" x 12" pieces of acrylic:

• 1ea. 6mm translucent white
• 2ea. 6mm black
• 3ea. 3mm black

Acrylic cement and a needle applicator will be used to secure the segments.

You'll also need six sets of #6-32 x 1-1/2" screws, nuts, 1/4" nylon spacers, and wahsers to fasten each panel plus two 1-1/2" wood screws of those same diameters to mount the panels to a wall or piece of lumber.