The layout of the segments has been revised. Dimensions are as in the following drawing.
You can see that everything is now nicely symmetrical, aligned and has even dimensions in mm for all important features (segment width, supports between segments, character height). I did this to have it scale down nicely to 50mm (segment-width is 5mm in that case) and bigger is easily scaled too.
Optical correction of the corner-segments
This is something that always annoyed me with this font. The marked corners do no look aligned, though they are perfectly in line. They seem to stick out a bit. This is an optical thing, which needs to be corrected by an offset.
Here's the version with corrected corners:
LED's per segment
For the 100mm font-height 3 LED's per segment are used to achieve the "top-to-bottom rainbow effect" I want to have with the finished 4-character-display (plus separating colon)
I want to show the time as 24 hour format plus maybe temperature and/or date.
Many different PCBs for each segment would result in no bulk discount at most PCB manufacturers, so I created one PCB, which can be used for every 7-segment-letter including the colon.
Later there will be four "dumb" segments with just LED's and one smart segment, which in turn controls the four others.
Each segment has all LED's in series plus an input and output connector. A solder bridge tells the "smart segment" which one is first and which is last.
Control of the Segments
One master-segment has all the parts placed to control further segments. The programming is done via USB (CH330N USB/UART bridge). It uses the same driver as the well known CH340 from all those cheap Arduino clones.
It has three pots (yes pots, not rotary encoders) to set the time and color of each/all segments. As the clock works in HSV-color mode, there's one pot for each value.
Reducing the overall height
This step includes two aspects:
- setting the LED's in into the PCB
- adding more diffusion because there's less overhead space for the LED's light to mix now
Setting-in of the LED's
This is done by creating a slightly undersized cutout of 4.9x5.3mm in the PCB for each LED. This makes soldering much easier. LED's are pressed in by hand with little force. There's no need for further aligning, just solder them from the bottom-side and you're done.
PCBs are from Aisler this time as they only take 8 days from uploading Gerbers to your mailbox if you live in Germany. I already asked them about their cutout-quality. Edges are not as straight as I am used to by OSHPark...
You can download the KiCAD footprint here: https://cdn.hackaday.io/files/20142861755328/WS2813_sunken_final_Aisler.kicad_mod
It is not possible (at least not in KiCAD 5.0.1) to draw lines on the Edge Cuts layer. If you wonder how it's done: draw the cutout on the DWG User layer, save the file, open it in a text editor and substitute your "layer dwgs.User" with "layer Edge.Cuts":
Save your file and close/reload your KiCAD. Be aware that modifications to these lines in the KiCAD footprint editor will give you errors, telling you it has detected segments on unsupported layers. Just click "Cancel" and you're fine.