22 May
2012
22 May
'12
2:16 p.m.
On 22/05/2012 19:44, Tony Duell wrote:
Mine
seems to be clever enough to stop without damaging the feed holes....
Hi I have a
high speed reader to but I've had troubleswith rubber bands. Th=
ey leave gunk on the tapes andlayers stick together. On a high speed reader=
=2C itrips the tape before one has a chance to stop it. Mine is a parallel =
A
procket-fed optical reader will wreck the feed holes if this occurs, a
capstan/pinch rolelr one will normally just stall the tape with little
damage. But I think I'd seaprte the layers by hand first just to be sure. one and I just
connected it to theprinter port ( guess that dates my laptop=
). A simpleprogram reads the data and puts it into files. On making a read=
er=2C the ideas of using a pile ofphotodiodes to read a punch card doesn't =
makemuch sense. It might be better to have a LED lightat each hole position=
Cards
are a pian becuase there is no equivalent of the sprockeet track
and there canb be totally blank columns. I think the commercial reader I
have (A Documation M200) takes a siming refernece from the leading edge
of the card and resyncs on evry column of holes it finds. It's still not
pleasant.
I haev a small mechancial card reader. This has an array of 40*12 contact
switches. You put a card in (only half of it), a solenoid fires and
liftes the card agianst hte scwitches. Where there are holes in the card,
the sensor wires pass through said holes, allowing the switches to remain
closed.
YEars ago I built an RS232 interface for it. You have to put the card in
one way round to read the first 40 columns, then turn it over, put the
other end in to read the last 40 columns. And yse I did revese the scan
direction so that the data comes out in the right order.
These days even I would probably do that with a microcontroller. Back
then I did it with a board of TTL.
-tony