Requesting help w/ RPi Project.

The RPi has 17 available IO pins. So driving 64 panels is going to be a challenge.

You could arrange them in an 8x8 matrix, but there is another potential problem. The amount of current you can draw from the IO pins of a Raspberry Pi is very limited, you may not be able drive 64 panels.

We need more information:

- What kind of light source are you going to use?

- How large/bright do these panels need to be?

- Are they each going to be a single colour or do you need them to change colour?

- Do you just want to turn them on and off or do you want to control the brightness?

- How far from the RPi will they be mounted?

- Is there any thing else the application needs to do beyond control the lights? 

If you want advice on any of the above that's fine, but some of these I suspect are already fixed by what you want to do.

- Derek

Derek Campbell wrote:

 

The RPi has 17 available IO pins. So driving 64 panels is going to be a challenge.

Look up the Microchip GPIO Expanders MCP23017 / MCP23S17, these are 16bit expanders and you can daisy chain 8 of them per i2c bus or SPI chip select. By my count that lets you have 256 IO pins using just 5 on the Pi.

As with any GPIO expanders, you're going to be limited in some way on the frequency you can update them, but as Peter didn't specify what his lights are we have no way of knowing if that's a problem.  Simple number of GPIO pins isn't a problem.

The lights in the panels are regular LED-Tubes, like one might find as a Christmas decoration. They should be individually controllable, and some kind of brightness control would be nice, but not necessary. The panels will be used as regular room lighting.

@selsinork: Yes, that is a possibility, but depending on exactly what Peter wants to do, that may not be the cheapest or best solution.

I did not want to be recommending IO expansion without knowing the requirements.

Let's see what he needs to do. :-)

@selsinork: Yes, that is a possibility, but depending on exactly what Peter wants to do, that may not be the cheapest or best solution.

I did not want to be recommending IO expansion without knowing the requirements.

Let's see what he needs to do. :-)

Derek Campbell wrote:

I did not want to be recommending IO expansion without knowing the requirements.

Well, as you observed, 64 into 17 doesn't go, so one way or another you're talking about expanding the number of outputs.  Beyond that is up to Peter.   Cheapest and 'best' don't necessarily end up being the same,  'best' may end up being not to use an RPi, but choose something more appropriate to the task ?

As I mentioned, by multiplexing you could fit it into 16 outputs, much like a seven segment display is driven.

As you suggest, I'll leave value judgements to the implementer.