24 May
2012
24 May
'12
12:25 p.m.
On Thu, May 24, 2012 at 3:01 PM, Dave McGuire <mcguire at neurotica.com> wrote:
Most likely. The design from Byte happens to take advantage of
asymmetry in the phototransistors (at least in the parts they had at
the time) by installing the sprocket sensor in an orientation that
gets light on it later, to give the data holes a little extra time
over the data phototransistors before the latch fires.
Now that I have a liquid-resin 3D printer to play with, and with upper
surfaces that are parallel to the exposure plate having a natural
smooth finish, I was contemplating making a printed shape that is
essentially a 2"-long block with a 1"-wide "groove" and a line of 9
holes to install phototransistors under. Unfortunately, at around
$1/g of resin, it's probably cheaper to send a part like that out to a
machine shop and have it milled out of Delrin.
-ethan
What would be
needed would be a guide for the tape, and a block with holes
drilled for the photocells, including a photocell aligned for the sprocket
holes. ?Just pull the tape past that block of photocells. ?When, and only
when, you get light through the sprocket hole, then look at the other hole
positions.
?Um. ?Is that not what the design that's been floating around (the one
with the 555s) does?