Neural Net Using LEDs?

Has anyone created a neural net where the weights are expressed as varying brightness of LEDs? That would make it interesting to watch how the net learns and how it responds to queries.

When the net used 4 bit weights the LEDs would be in one of only 16 difference brightness levels.

Instead of LEDs, which would draw a lot of power for a 1M array, it would be useful to use one of the huge screen TVs.

Even more interesting would be the ability to see how the various "expert" subnets interact.