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Controlling 100 LEDs


#1

HI Folks,

yesterday I stumbled about this: http://qlocktwo.com/
Its a total awesome clock!
But I saw the price tag with about 850€, this fine piece of art is way too expensive…
So I thought this should be no problem for my Spider board.
But sadly there arent enough IOs.

How can I solve this?
Are there any modules expanding my IO Ports?

Maybe I dont need IOs only some Outputs to turn on and of the LED…

Any help appreciated :slight_smile:
Thanks :slight_smile:


#2

Maybe something like this… :wink:

http://www.ghielectronics.com/catalog/product/361


#3

I just stumbled across this:

IO60P16 Module
http://www.ghielectronics.com/catalog/product/363

So basically I buy two of them,
wire the LEDs up,
write some Code and Im done…
Right?


#4

That would work also. I like the chainable nature of the MaxO module, though.

EDIT: Beware that both of these modules are brand new and drivers do not exist for them yet.


#5

:slight_smile:
You must have read my mind.
I was just checking out Gadgeteer Source to browse through the new drivers :slight_smile:

Maybe I am able to write those drivers by myself…
Right after I understood how to use those shiftregisters :wink:


#6

That’s certainly an option. I suspect, though, that we’ll get a new SDK in a few weeks that will contain these drivers if you want to wait.

You’ll also have to figure out SPI if you’ve never used it before.


#7

This one would be easier plus it has current-limiting resistors already, but both will work. http://www.ghielectronics.com/catalog/product/361


#8

Awesome clock! Believe me, the time you spend on the driver will be peanuts compared to the time you will spend on converting the current time to a readable sentence :slight_smile:


#9

There are arduino examples out there (here’s one: http://www.instructables.com/id/Sleek-word-clock/ Page 7 has the code), so i don’t think he’ll need a lot of time coding :wink:

Wonder if I should make one in dutch :smiley:


#10

http://makeprojects.com/Project/Small-Word-Clock/2135/1

This guy took a more interesting approach to spreading out the words…


#11

@ Eric: I really want to make one in dutch. The only thing I need is a little time :slight_smile:


#12

Can you really drive those without a constant current driver? FWIW, there are LED driver chips out there, but they typically support only 16 LEDs per chip.

Is 10mA per pin sufficient? That would be about 1/2 what a typical LED uses, right? Even at that, 100 LEDs at 10mA per LED = 1000mA, assuming you’re not using any sort of switching or multiplexing scheme.

Is that calculation correct? 1A is pretty significant draw – more than USB would provide.

I haven’t played with the maxio board. Looks really cool.

Pete


#13

MAX7219 (two of them) gives you plenty of LEDs. Remember, if it can be run from an Arduino, it can probably be run from a single Gadgeteer socket.

You shouldn’t have enough LEDs on at any given time to run into current issues.


#14

@ Pete: for the clock, only a small number is on all the time, so that will not be the issue

I do wonder how they power the wall clock…


#15

@ Wouter, @ godefroi

Good point. When I see 100 LEDs, I tend to think they’ll all be lit. But you’re right.

As long as he’s not doing a 5x20 inverse digital clock or something :wink:

Pete


#16

@ Eric: they have a dutch version of the clock, see this page http://qlocktwo.com/info.php?lang=en and wait until the image scrolls to the left (it’s the purple one)


#17

Really?
I thought of time to sentence conversion in less than 2 hours…
Writing tests: 45 min
Making them green: 1h

The conversion between the sentence and which led has to be lit up is a piece of cake…

SPI and Shiftregisters give me much more headache…


#18

@ Wouter, cool