If you were wandering around Prague this Christmas season you may have spotted a Raspberry Pi 2 controlled Christmas tree. But you had to look quick because it was on the back of a special tram car that lubricates the rails around the city to reduce noise. The colors on the tree were determined by a web site that allowed visitors to change the colors. The same system, with a few adjustments, controlled a tree in the entrance hall of Czech Technical University in Prague at Karlovo.
The adjustments weren’t trival. Power was a problem, for one. The electrical noise from the tram’s drive motors needed to be filtered by using a switching power supply. Cold temperatures might have created a frozen Pi so they added a heater. After all, everyone loves warm Pi. The LEDs on the tree were handled by a WS2811 addressable LED driver chip.
You can catch the tram any time on the web, but the tree will be gone once the Christmas season ends.
The stream:
http://slowtv.playtvak.cz/prave-ted-mazaci-tramvaj-jede-prahou-d73-/mazaci-tramvaj.aspx
Fun stuff though a build log or some other specific info would be nice.
How important is the “Cold temperatures might have created a frozen Pi so they added a heater” part since it’s not running on batteries? I don’t think Prague gets particularly cryogenic
I’m sorry we haven’t provided more details (you can read a bit more on the linked site). We thought it’d be nice to show it now while it’s still working and we may be able to write about it more later.
Temperature is an issue even in non-cryogenic Prague :). If the temperature drops to approx. 0°C the RaspPI doesn’t boot up. Sometimes a tram driver turns the tree off at the end of the line (it’s powered from a safety beacon), it cools down and we’re in trouble because it doesn’t start up.
A lot of silly decisions, the Pi does not care about the low temperature, it DOES care about condensation and a nema 4 plastic sealed enclosure with a discarded silica gel pack will fix that
Of course, it’s possible, but the box was closed in the cold air so there should not be much to condensate. It’d be nice to test it later. I’ll be happy to hear more about other silly decisions.
“CZECH OUT…” Ha ha, I get it HaD! You guys are soooo clever :-D