In the early 60's Hasbro took advantage of the growing interest in "computers" to sell a cleverly packaged trivia game called Think-a-Tron.
Before you can begin to understand how Think-a-Tron works, you need to see it actually running. This video does a great job of explaining how to operate a Think-a-Tron.
I'm in the process of making a Think-a-Tron workalike. For more details about this project see: Think-a-Tron 2020.
This tutorial is about just one of the elements on the original Think-a-Tron that I wished to capture with some fidelity, the 5x7 "LED" display.
I was surprised to learn that this display was purely mechanical! This was accomplished by shining a light trough a spinning disk (seen below) onto a 5x7 array of plastic lenses. It was a great effect. Very clever.
My 2020 implementation takes advantage of modern, individually-addressable, RGB color pixels. This is a pretty simple build so let's get started.
Supplies:In addition to the printed parts you will need:
- BTF-LIGHTING 100pcs WS2812B Addressable 5050 Smart RGB LED Pixel Light on Black Heat Sink PCB Board for Arduino 5V DC - Amazon
- Some 30 awg "wire wrapping" or similar wire.
- 4 - M2 x 6mm bolts.
I printed the parts with the following settings (unless otherwise specified):
Print Resolution:.2 mm
Infill: 20%
Filament: AMZ3D PLA
Notes: No supports. Print the parts in their default orientation. To make a 5x7 NeoPixel Display you will need to print the following parts:
- 1 - LED Array Box
- 1 - LED Array Diffuser - Note: It's all one piece, printed at 0.10 mm. I printed the black backing panel, paused the print at the 1.10 mm mark, then finished with some "transparent" PLA filament.
The panel on the original Think-a-Tron is 50 mm (2") wide and 70 mm (2 3/4") high and I wanted mine to be the same size. I searched for a suitably sized LED array but came up empty. I was about to start creating a custom PCB when I found some NeoPixel compatible, WS2812B addressable, smart RGB LED pixel lights. They are individual units but ship attached in a 10x10 grid as can be seen below. The good news for me is that each pixel light is about 10 mm in diameter which is perfect for my purposes.
With a little careful bending it was easy to snap off a 5x7 block of these. As shipped they are not connected so I had to wire the individual units in my 5x7 array together. I used some 30 AWG "wire wrapping" wire that I had lying around from the old days ;-) It was a lot of pads to wire but not too hard. Use the photo below as a wiring guide.
The pixel lights shipped with a three wire connector that I attached to the panel.
- Press the diffuser panel into the front of the display case with the "domes" facing forward.
- Place the LED panel behind the diffuser with the LED lights facing forward, and the wire leads aligned with the slot in the case.
- Use 4 M2 x 6 mm screws to attach the back of the display case.
For testing purposes I connected the display to an Arduino Nano:
- Red wire to +5V
- Green wire to the D6 input
- White wire to GND
I wrote a short sketch using the Arduino FastLED library which is posted in the Code section below.
And here is the 5x7 NeoPixel Display in action:
Step 5: Final ThoughtsI have a pretty specific use for this Display, but I hope you see that the same techniques can be applied to any sized pixel array.
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