16 Mar
2013
16 Mar
'13
2:46 p.m.
The HP 9320-2051 cards have timing marks. That really
helps vs an
IBM Hollerith card that uses a constant-rate feed mechanism and
Indeed, those timing marks will help a lot.
timing from the front edge to locate the data. One
idea is to have
a microcontroller (Arduino with nootropic design Video Experimenter
shield or a Raspberry Pi with a USB web cam, etc) positioned such
that it sees a vertical slice of the card, filtered through a red gel to
obscure the printed background, and when two timing ticks are visible
(detected via either camera image decoding or perhaps a pair of spaced
phototransistors to a "trigger" input), snap a tall, narrow frame that
represents one column and look for the dark spots in the right places
and turn that into an ASCII character and emit it out the serial port
(both the Arduino and the Raspberry Pi can do this).
<Shakes head>
I don't have the HP mark sense reader on my 9830 (I wish I did...), but I
would guess it used a dozen or so phototrasnsitors as sensorts and a few
hundred transsitors (iniside ICs) at most to process the signals. You are
replacing this with somethign with a few million optical sensors and a
few million transsitors. And thsi is progress?
<sahkes head again>
-tony