So, this is log 5.
I've been busy over the past 2 days. The new BLUE LEDs arrived ( 3528 SMD PLCC) 500mcd. Wow these things are bright! The white block in the photo is one LED ( hobby knife to give some scale to it)
I created a base where it is easy to mount the LEDs on the bottom and slide the filament in the top. It was printed on my 3D printer - and the first prototype worked very well. Took 10 mins to design and 14 mins to print.
This is the bottom view.
So, my idea fort he base seems to work, in this one, I can fit 12 LEDs in the base, allowing me to use 2 LEDs to drive some numbers.
for instance, the number 6:
Now let's light the blue touch paper and stand well back!
Hey, looking good.
If I make the base in Black PLA, instead of white, the bright-spots from the LEDs will be covered - and then only light will escape via the digit itself.
I want to experiment with the idea from @Chris Knight - to put foil on the open end and see if I can reflect the light back into the filament.