wouter van ooijen wrote:

>> Since you have the wires from master to each node anyway, why not keep
>> all the control logic central? This is probably cheaper.
> 
> He wants three LEDs (or a 3-color LED) at each node, and estimates that
> the cost of the extra wire(s) offsets the local intelligence (I
> disagree!).

I haven't run the numbers, but my gut says you might be right :)

Peter, if I understood you correctly, so far you've been talking about a
central unit with some hundred communication+supply drivers for the nodes
(one per node) plus the nodes themselves. Are you sure that the cost of the
extra pair of wire is not offset by the extra PCB plus the extra components
on /both/ sides (node and central)? You want two-way communication, and
just stringing all nodes in parallel at the central probably needs RF or
audio communication. The simpler voltage level thing won't work well --
imagine the currents you need to draw to make the voltage drop. In order to
use this, you have to have individual drivers at the central, or at least
in clusters.

Depending on your requirements, there may also be the possibility to use
some 5 or 10 sub-centrals, controlling 10 or 20 LEDs each. These can then
be connected to the central with more wires (separate supply and comms). 

Gerhard

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