[dorkbotpdx-blabber] another LED array question

[Mykle Hansen]

On Dec 15, 2008, at 3:47 PMMonday, Mr.T wrote:

> if you don't mind clocking them at a mere 15 MHz you can cascade all  
> 5 of
> them and only use 4 pins of your arduino

aha!  a smart person!  i'll be stalking you later.  =)

i think i get the concept, actually ... this will be my
first time with shift registers, so bear with me.  is it
true that with the right cascading pin connections between
chips (shown in the datasheet, i think) somehow all
N chips turn into one great big linear 12x24xN array, and
i only have to shove 288xN bits down the serial link
every time i want to update anything?  it seems like that's
what i'm reading: i just rewrite the whole shebang every time
i want to make a change, rather than addressing each pin
individually with an address+value.  unless i'm getting
this wrong.  but i can do that, sure.  at 15 mhz, that's
still something over 10000 updates per second.


On Dec 15, 2008, at 2:19 PMMonday, Greg Grunest wrote:

> Yeah, that is an awesome chip too.  I also noticed the SMT only  
> packaging
> which is kind of a drawback.  Has anyone hand soldered one of those  
> chips
> with a thermal pad and been successful?

i gotta say, the 24-channel chip is pretty nicely suited to this
project.  i guess i just gotta get real with my long-overdue
PCB-design learning curve.

qestion for jason/don/everybody: is it likely, assuming i can pull
off a 1-sided pcb design correctly, that i would be able to
get good enough resolution using the chemicals-in-the-sink
method that i can use SMT or DAP or QFM chips?  assuming i can
muster the jedi-skills of microsoldering, would i even be
able to get the teeny pads and traces right?

my other anxiety is how to heat-sink them.

> The 8-bit version that comes in dip packaging has a ton of
> potential.  I'm going to have to order a couple and see if they  
> drive hobby
> servos.  That would ROCK if you could drive 16 servos with two of  
> them all
> from a serial line on the Arduino.

when you say "the 8-bit version that comes in dip" do you mean
the TLC5917, in "16PDIP"?

the other thing my project needs is some stiff, poseable
4-wire leads terminated in some connector that i can just plug
the 4 leads of an RGB right into.  if the wire is poseable,
then the PCB could look more or less like anything.

-m-

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