Latest Project: homebrew paper tape reader - test-drb@ccmp.vtda.org

11 Dec 1998

Richard A. Cini, Jr. said:
...
     I saw a project in one of my old Bytes for a
hand-pulled paper tape
reader. Very simple - 9 photodiodes, a light, a latch, a pulse-stretcher,
and some guide posts.
    Well, here's the parts I have lying around: a BasicStamp-II, two R/C
servos modified for constant running, a few switches, and photodiodes.
    If I get this thing working over the Christmas holiday, I'll post a
construction article.
    Any recommendations for rubber pinch rollers? I'm thinking rubber
stoppers from a plumbing supply shop. These are pre-drilled and come with a
washer, bolt, and wing nut. 
FWIW, I have a "store bought" manual tape reader about the size of a small
candy bar. The circuit board inside has the row of detectors (9 in all),
and two hex TTL bus driver ICs, and that's it. On the outside, a piece of
black
tape with 9 holes punched in it, covers the detectors. Over this is a strip
of clear plastic supported by four very short nylon stand-offs. I insert
the paper tape under the plastic and between the stand-offs. That's all thats
needed to keep the paper tape alined and flat against the detectors. Room 
light is used to detect the holes. The output is 9 bit parallel, which I
connect to a VIC-20 user port with the spocket hole output going to the
interrupt line for that port. Unfortunately writing the software to read 
tapes is one of those projects that I have no gotten back to.
  As far as lighting goes, the Heath H-10 uses a neat trick. In it they
use a automobile tail light bulb which has a filament about an inch long.
They position the bulb so that the filament is directly over, alined with,
and parallel to the row of detectors. This gives uniform illumenation to all
the detectors.

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Doug Coward	           
Press Start Inc.          
Sunnyvale,CA    
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