Help Working Out A Components List


Tobriand

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Heya!

I had an idea today that would be very cool for the shop where I work, and potentially not too pricey. Potentially. However, knowing nearly bugger all about electronics, I'm having trouble working out the specifics of what components I need. Effectively I'm trying to build an LED array, but with the LEDs very distant from eachother, and ideally in such a way so as to make each one modular - i.e. you can attach further LED-blocks later, and they'll work out their own identifier in the array. A CPU elsewhere then tells them when to light up and when not to. That chip probably won't be an issue - there's only one of it - but the one for the rest of the LED-blocks might be, since I can't see an array being fewer than, say, 400 units minimum. Which means, even if I'm going for a z80, I'm likely to need £600 of them lol.

I'm after a chip that can:
- Interpret a signal, ideally two, bearing 1-2 bytes of information (a number from 0-65536; probably will never go above 100 though)
- Add one to it
- Output the new signal in the same format as it came in.
- On receiving a separate signal, check to see if it is meant for it, and if so, light an LED
- On receiving a final signal, turn off the LED
- Remember the number it generates from the original signals indefinitely.

Ideally, it wouldn't be outputting the number it's come up with constantly, but only on a further trigger event, to save on power.

So... any ideas?
 
Not quite sure what you're trying to accomplish overall?

Anyway, if you're trying to set up a large array of LEDs which are "controlled" through some sort of serial protocol, then I'd imagine that rather than having each module auto-identify its location, it might be simpler (and cheaper?) to have a simple set of jumpers on the board to manually configure the address of the module (i.e. you could address up to 1024 with only 10 jumpers).

What's the purpose of "adding one" to the number being passed? If you must do this, counting can be done with a simple logic chip (or a number of them daisy-chained if more bits are required). Check out 74161 and 74163 - These are synchronous counters (4 bits only) with preset and reset - the "synchronous" part is important as this means that all bits are changed simultaneously (as opposed to a "ripple" counter where changes "ripple" through the bits meaning there can be a slight delay while the change propagates through all bits). The preset means they can be pre-loaded with a desired value and then a single "clock" pulse will add one to the count. These can be daisy-chained fairly simply so you could obtain 12-bits with only 3 chips. The chips cost approx £0.18 each for small quantities, no doubt larger numbers would be cheaper.

Remembering the number isn't that difficult, that could be done with logic also - 74116 is a dual 4-bit latch So you'd need a couple to handle 16-bits.

If you really *want* to have a Microcontroller doing the donkey work, PIC chips can be had for as little as $0.50 in 25+ quantities (PIC10F series) or $1.80 (PIC16F series) and as they can be implemented without external memory and in some cases without external oscillator they are extremely cost effective. They also come with a number of I/O pins (PIC16F685 @ $1.80 has 18 I/O pins for example). The Zilog Z8 is also an effective microcontroller (it can implement the i2c protocol fairly easily), but I couldn't find them available cheaper than PICs ;)

Without understanding a little more about what you're hoping to accomplish in general, it's hard to give more constructive advice - for instance, will the array have a limit in one dimension (i.e. width or height) ? This could be very significant.

Don't know if any of this helps?

Tony
 
Well, the idea is to make it possible to add to the array for different situations, so whilst it could have a limit (say, I can't see the original idea being more than 1byte, or possible two, in either direction), the chances of it actually reaching that limit should be slim, if only to allow for more to be added.

Thanks for the advice though - will look into theose components later. Now must head for work, though!
 
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