The PCB (Christmas) Tree 2021 update (#P32F1)
Ah yes, the good ol’ PCB tree.
It wasn’t in use for a good part of 2021 due to the fuse burning out, unclear if it was from an accident (some parts are still wobbly) or just slightly specced too low at 1.6A (slow-blow, but 24/7 operation). Since it was placed inside a somewhat difficult to access triangle cavity of PCBs, it took me a while to open it up again and move things outside. Voltage of the DC-DC converter was lowered slightly to around 3.2V and the single fuse was replaced by two individual units placed on the outside, dividing the power rail roughly equal between upper and lower tree (by current, not by physical size)
Well, Covid legislation crap and everything happening, the tree once again has received a significant upgrade in December. Fuses are now at 1.0A each, a couple of dark(er) spots were patched, and the previously bleak X-shaped trunk (see above) is now populated with two more rows of scrap PCBs. Since that would make it sit uneven on the table, a new triangular trunk plus pedestal was fitted in such a way that it can be unscrewed from the side, not just from the bottom (the latter is a pain in the ass to disassemble, the former is a royal pain to make). For future catastrophic events, it can be split here with just the power rail to be disconnected and repaired without the unwieldy other side hanging onto it.
I also prepared two more layers for the new trunk, but ran out of LEDs in the process. Even though 100pcs packs seem to last a long time – at 40cm diameter, A LOT of LEDs go into each layer…10mA each also add up quickly!
Interestingly the price of these specialized LEDs has only gone up on eBay (~6€/100pcs), while I was able to buy packs on AliExpress for 2.55€ including shipping and, major change in 2021, local VAT (19%). We’ll see if they arrive, though, but I’ve bought all of those LEDs from the very same seller so far, so I’m confident they will.
With those future extensions, the tree now also includes networking adapters, PCIe risers, RFID readers, LCD panel drivers, attendance recorders, DDR2 memory and SSDs. The large unlit PCB sitting underneath is an entire dual-socket 1366 mainboard, which will need to be cut in the center instead of neatly arranging boards around the trunk. Both layers will likely be supported there by thick copper strands which are already in use for PCB interconnects.
Current strategy for making the tiled layers is to fix the initial arrangement by hot snot on the PCB edges, then adding the copper reinforcements, then reflowing the hotmelt for a nicer finish. Once a common ground plane is established (not everybody pours ground planes, and not every ground plane is touching mounting holes!), the LED locations are chosen, LEDs are added and fixed in place, then connected together.
Total power consumption has gone up to between 6 and 10 Watts, not that much more than previously recorded thanks to the slightly lowered voltage. It will however require a second DC-DC converter once the two bottom layers are finalized and put into place, in order to not exceed the “3A max” rating of the first unit during “boot”. It’s not all that critical when everything is random (hence the 2x 1A fuses), but for one cycle at startup all LEDs reach peak power at the very same time. Adding a secondary converter and a third fuse also helps in separating the sections of the tree. Not much after that, I will need to exchange the 802.3af (15W) power module for an 802.3at (PoE+) one that is capable of delivering 30W. The PoE+ switch (and power supply) is fine so far – once I exceed those 30W, I’ll happily switch for a local power brick underneath the tree
Overall size (height), by the way, has increased to 65cm and total weight is a tad above 4kg. This is proper tabletop Christmas tree size now!
Although YouTube is pushing portrait video and especially their dumb “shorts” so much, they (as well as WordPress) still cannot do embedded 9:16 video properly. So here’s the standard video box with rather tall content, same speedup steps as last year (25fps standard and 120fps mkv mod as first speedup, then a downconversion to make 20x, and finally another 2.5x high fps version of that one to make 50x)
And this is the static dark version – still a bit lopsided near the PoE in, but it’ll do and every new layer is now fitted to an envelope to make it more symmetric over time. Probably won’t fit the table anymore in 2022…