And So It Begins

A project log for 16 Inch 7-segment LED

This will be a giant LED numeral made with neopixels.

David WheelerDavid Wheeler 12/17/2018 at 01:280 Comments

This is a project I've been wanting to tackle for a long time.  The idea is to use these giant LED numerals for cheering on our robotics team at competitions.  And with the Christmas break nearly here and robotics build season starting in January, it seemed like this would be a good time to get started.

Yesterday afternoon, I sketched out the basic design.  (See the gallery.)  Each of the seven segments is illuminated by neopixel LEDs shining in from the side.  The volume of each segment is actually a white 3D printed shell that's open on the top.  When viewed from the front, the LEDs shining on white plastic will hopefully give a nice uniform lighting effect.

The neopixel string will be controlled by an Adafruit feather with BLE.  This should enable a group of digits to be controlled by a single cell phone via an app.  I also want the operator of each sign to be able to program simple sequences without needing a phone.  So there will be a simple OLED display on the back with a group of buttons.  I'll figure out some user interface later in the project.

Today I picked this up again and worked out a rough Bill of Materials.  I'll post details on that later in the project, too.  For now I estimate each digit will cost about $150 buying all the components from Adafruit or Sparkfun.  So four digits will set me back about $600.  Ouch.  Still, I don't have to spend any money just to get started.  First I want to figure out if the design is feasible.

Since the idea is to use 3D printed wells for each of the segments.  I thought I should try to CAD up the shapes in Fusion 360.  I'm a bit of a neophyte with CAD tools so I wasn't sure if I would get through this without hitting a stumbling block.  But I did succeed in developing the necessary shapes.  There's a vertical segment, a horizontal segment, and a "dot" segment that will form a colon if I want to display the time.  Each segment has "windows" for the neopixels to shine in from two sides.

When assembled, the whole design looks pretty sharp!  That's helping motivate me to carry through.

The 3D printing time for one set of segments is estimated at just over 60 hours.  (Ouch again.)  I'll get it started tomorrow morning when I get to the office.  (Yeah, I'm using company equipment to make the prints.)