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Gabriel Morell





Train Sign
posted Nov. 27, 2017, 6 p.m.
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Train Sign

I had a bit of a problem with ordering random LEDs on Ali so when I saw 8x32 WS2812 LED arrays for a good price I jumped on them. A while after the displays arrived I was looking at the train signs on the MBTA platform and was inspired. I did some measurements and designed an enclosure in Inkscape. I wanted it to be visible from across the room. It features an acrylic diffusal layer infront of a grid of holes on the layer below. This allows the light to be contained to the segment below and then has it diffuse on the layer above. After some initial trouble with scaling to fit the array, I finished cutting all the parts at the local space.

Cut and Assembled

Cut and Assembled

Cut and Assembled 2

Cut and Assembled 2

Assembly

The box was assembled and the electronics put inside. A hole was cut on the other side to run a USB cable in to power the ESP8266 and Array.

Electronics Assembly

Electronics Assembly

A quick of the back napkin calculation notes that the display at full white will draw over fifteen amps, so I had to be careful to limit the style of the display.

Grid Testing

Grid Testing

Software

The first test involved figuring out the electrical order of the array. This was done by iterating over values and noting how the array was filled.

Abstract Train

Abstract Train

From there the implementation was incredibly abstract and was a series of lines representing trains and how far away from the stop they were. This was done by publishing to an MQTT topic and doing some transformation on the time and spreading it across the display. In the image above, there are four trains within twentry minutes of the station, the green ones ten+ minutes away, the yellow one less than ten and more than 3, and the red one imminent.

TrainSign Result Time

TrainSign Result Time

TrainSign Result Train

TrainSign Result Train

TrainSign Result Weather

TrainSign Result Weather

This implementation however, was not super friendly to people reading it so I created the Extensible Signage Architecture and gave it the data sources for time, weather and train distance.

In the next post I detail the architectural considerations in building the Extensible Signage Architecture.

 
Extensible Signage Architecture