I received my order from Bricklink! Amongst the blocks were the 2×4 bricks that I needed to contain the circuit board.
Here’s the final light brick!
Power (5v) on the right. The green wires are the ICSP connenctor. The beacon connects on the top.
Milled out and drilled block.
The small hole (5mm) is for the switch, the large (8mm) is to make enough space for the beacon connector
Inside the block is all milled out with the Dremel.
There you go. It’s kind of crude, but it works.
I think for the next version I’ll use some more standard connectors and bring them out the side of the block rather than through the top. But for this version it works just fine.
The 4×2 plate fits on the bottom to hold everything together.
Catmacey's stuff 
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Hello, Catmacey,
you have made some amazing things here and it is fun to watch and learn. This DIY beacon would work fantastic for a project that i got started (http://www.eurobricks.com/forum/index.php?showtopic=95344&st=75#entry1920352) in order to make my 5-year old son a very special birthday present. The whole thing got a bit out of hand and i suppose he will rather get it for his 6th. I would be grateful if it would be possible to contact you about the beacon, in case you can find a spare moment for that. I’m a beginner in electronics and would appreciate some advice very much.
Thanks for sharing this and other great little inventions!
VintageCharlie
Hi VintageCharlie.
Glad you liked it. It’s been quite a while since I worked on that project that I had almost forgotten about it.
Hi Catmacey,
Read your thread…just awesome, very nice work! When you finalize the design do you plan on selling them. I certainly would like to add some of these to my sons lego’s. LMK! Thank you!
AT