[sdiy] super-nice LED interface ..

[The Old Crow]

  My guess is the 8x8 dot-matrix LED block is scanned in rows (see the 
start-up "lamp test" at the very beginning of the video) and uses eight 
sense amplifiers via a simple switch array that keeps the active row 
from saturating the sense amps.  So, a single instance of the sense 
action would be, light up a row, then "scan down" the adjacent unlit row 
or rows by sampling the sense amps with an 8-channel A/D (probably in a 
PIC or AVR part or some other uC).  Then store the values, change to the 
next row, sample...and so on.

  For noise immunity (ambient light), perhaps the lighted row is pulsed 
at some carrier rate, like..oh, 40KHz (like IR remotes) and the sampled 
signals are sifted for the carrier.  Some other bit-frobbery ensues, and 
the pretty LCD display of the repsonse is the result.

Crow
/**/

Ian Fritz wrote:

> Oh I see, it's a scanner?  Not quite clear on exactly how that thing 
> works.  If your finger was between two devices then there would be 
> strong coupling when one is an emitter and the other a detector.  But 
> if you move away towards one of the devices wouldn't the coupling get 
> weaker?
>
> At any rate the cartoon shows a whole set of alternating devices 
> emitting, so the scanning aspect isn't very clear to me.