Gus,

Some questions that might help define the optimum solution might be:

Is this for indoors or outdoors?
If outdoors, does it require being lightning proof? rain or snow proof?
Is this for low ambient light or full sunlight?
Is this a one off or will many be produced?
Is this cost sensitive?
Do you have a rough budgetary cost estimate?
As an antenna structure will this annoy all the hams in the next county?


On 6/1/2010 12:36 PM, YES NOPE9 wrote:
> I am considering building an LED array to hang on the side of a tower.
> LEDs would be attached to a lightweight grid.  The grid spacing is to
> be determined.  Initially the LEDs will be white for night viewing.
>
> The array may end up being 50 by 30 feet ( height / width )
>
> I was considering using a chip such as the DS2408 which provides
> one wire communication support and 8 I/O pins.
>
> Then I thought that it might make sense to use a PIC MCU instead.
> The idea would then be a low cost PIC with 8 GPIO and some kind
> of multi-drop or pass-through communications.
>
> Power to the MCUs and LEDs might be on separate feeds.
>
> JAL seems like a good language to use.
>
> The number of LEDs to be individually controlled would be in
> the range of 1500 to 6000.  Updating all the LEDs once per
> second would be cool.
>
> #1   What would be the best communications scheme and method
> of identifying each MCU uniquely ?   Would it be better to use
> fixed IDs or dynamically assigned IDs ?
>
> #2  Would it be a good idea to find a PIC MCU with a built-in
> supply regulator ?   The distribution of power to MCUs and LEDs
> is an interesting one.  Should I use high voltage / high
> frequency AC to distribute the power ?  This would mean smaller
> copper wires and transformers.
>
> #3  Since I want as little "stuff" hanging on the grid as
> possible I imagine the MCU should have a built -in oscillator.
>
>
> #4  A low cost way to drive the LEDs ( which are not chosen yet )
> might be a FET per LED.    I am trying to think of a clever way
> to control the LED current.  One idea was to produce *10 volts
> peak AC from the output of a step-down transformer , put a diode
> in series , an inductor in series , the LED and the FET to common.
> I could switch the FET for a given time and then switch it off.
> The total amount of current would depend on the on-time.
> Maybe it would make more sense to use a resistor in series rather
> than the inductor.
>
> ( * The 10 volts is chosen to give a starting point to the design )
>
> #5  The ability to remotely load new code into the MCUs  could
> be useful.  It would not have to be a fast process.
>
> When I was using the Microchip MCU parametric search, I did not see
> a filter for on-board power regulator.  Did I miss something
> obvious ?
>
>
> OR can all this be bought off the shelf ?
>
> Gus
>
>

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