Controlling 100 LEDs

HI Folks,

yesterday I stumbled about this:
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:

Maybe something like this… :wink:

I just stumbled across this:

IO60P16 Module

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

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.

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:

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.

This one would be easier plus it has current-limiting resistors already, but both will work.

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:

There are arduino examples out there (here’s one: 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:

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

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

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.


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.

@ 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…

@ 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:


@ Eric: they have a dutch version of the clock, see this page and wait until the image scrolls to the left (it’s the purple one)

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…

@ Wouter, cool