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hardware internet tech

Reverse Engineering An Old Bus Display

When his makerspace was once talented a couple of Luminator LED indicators of the type you could see at the entrance of a bus, [PWalsh] determined to tug one aside to look what made it tick. Along the best way, he controlled to opposite engineer its regulate protocol and substitute its unique regulate board with a WiFi-connected Raspberry Pi. Now they are able to use the LED indicators to turn no matter they would like; no bus required.

As they have been designed for automobile use, the indicators have been stressed for 12 volts DC. So the primary order of industrial was once becoming it with an AC/DC converter so it may well be plugged into the wall. After he measured the show’s present intake, [PWalsh] estimated it’s most power intake and made up our minds an previous ATX pc energy provide was once greater than as much as the duty.

With the signal fortuitously working battery-free, he may start working out learn how to communicate to it. Noticing a MAX485 RS-485 converter at the PCB, gave a horny excellent concept of what language it was once talking, and with assistance from his trusty oscilloscope, he was once in a position to suss out the baud charge. An inexpensive USB to RS-485 converter was once then stressed in between the signal and its regulate board so he may sniff the knowledge passing over the road.

From there, the overall piece of the puzzle was once finding out the captured knowledge and working out the protocol. [PWalsh] was once in a position to spot packet headers and ASCII characters, and beautiful quickly knew sufficient about how the signal communicated that he was once in a position to take away the regulate board solely and simply push textual content and pictures to it proper from the Pi. He’s even made his framework to be had for someone else who may have a an identical piece of bus-signage laying round.

Even if you happen to’re no longer taking a look so as to add one of those indicators in your lab, this challenge is an incredible instance of protocol opposite engineering with cheap equipment and easy tactics. We at all times love to look the method damaged down step-by-step like this, and our hat’s off to [PWalsh] for turning in the products in a large method.

This isn’t the primary time we’ve observed those kind of LED indicators get the “Internet of Things” remedy, and if you happen to’re content material with a slightly scaled down model, it’s good to at all times simply construct your individual show reasonably than ready at the native public transit car to get parted out.