14 Jul
2003
14 Jul
'03
7:07 p.m.
On Jul 14, 11:53, Fred Cisin wrote:
What about an under $10 one for a
MICROCOMPUTER/PERSONAL COMPUTER?
I will lay claim to the dubious honor of inventing that. (even though
it was so obvious that MANY people must have done so)
In 1983, I wanted a digitizer for blackboards. As a "proof of
concept", I attached a one foot long piece of clear plastic (a
ruler) to the shaft of a potentiometer. At the other end of it
I attached another potentiometer, with another foot long piece
of clear plastic attached to the shaft of that one. That made
for an upper arm hinged at the edge of the board with a
potentiometer, and a forearm hinged at the end of that with a
potentiometer at the "elbow".
There was a very similar device around in the early 1980s; I can't
remember what it was called but it hooked up to one of the machines at
the college I worked in then, so it must have been for a BBC Micro
(around 1983) or an Apple ][ or PET (about 1982). Its operational area
was about an A4 sheet.
--
Pete Peter Turnbull
Network Manager
University of York
15 Jul
15 Jul
6:24 a.m.
Peter Turnbull wrote:
On Jul 14, 11:53, Fred Cisin wrote:
Anybody else try depositing carbon ( either pencil lead or other
substances )
on a flat surface and work out the math to get X-Y?
Jim Davis.
What about an under $10 one for a
MICROCOMPUTER/PERSONAL COMPUTER?
I will lay claim to the dubious honor of inventing that. (even though
it was so obvious that MANY people must have done so)
In 1983, I wanted a digitizer for blackboards. As a "proof of
concept", I attached a one foot long piece of clear plastic (a
ruler) to the shaft of a potentiometer. At the other end of it
I attached another potentiometer, with another foot long piece
of clear plastic attached to the shaft of that one. That made
for an upper arm hinged at the edge of the board with a
potentiometer, and a forearm hinged at the end of that with a
potentiometer at the "elbow".
There was a very similar device around in the early 1980s; I can't
remember what it was called but it hooked up to one of the machines at
the college I worked in then, so it must have been for a BBC Micro
(around 1983) or an Apple ][ or PET (about 1982). Its operational area
was about an A4 sheet.
8:52 a.m.
Anybody else try depositing carbon ( either pencil
lead or other substances )
on a flat surface and work out the math to get X-Y?
More like everybody.
The math is not hard at all. With two sample points, you read
two voltages, from that mathematically get two circle radii, intersect
them and get at most two points. Sample three points and get just
the one point with a degree of redundancy to it. I would take the samples
by chopping back and forth from the different sampling points.
Others may have other methods, I don't claim to know them all.
Try finding a premanufactured carbon surface, or antistatic plastic
that is partially conductive. Trouble with carbon contact is that once
you put paper on top of it you've insulated it, so it is to be used as
mouse substitute only. An electromagmetic digitizer can take a
paper above it just fine.
John A.
4:03 p.m.
In 1983, I
wanted a digitizer for blackboards. As a "proof of
concept", I attached a one foot long piece of clear plastic (a
ruler) to the shaft of a potentiometer. At the other end of it
I attached another potentiometer, with another foot long piece
of clear plastic attached to the shaft of that one. That made
for an upper arm hinged at the edge of the board with a
potentiometer, and a forearm hinged at the end of that with a
potentiometer at the "elbow".
There was a very similar device around in the early 1980s; I can't
remember what it was called but it hooked up to one of the machines at
the college I worked in then, so it must have been for a BBC Micro
(around 1983) or an Apple ][ or PET (about 1982). Its operational area
was about an A4 sheet.
7850
days inactive
7851
days old
3 comments
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allain＠panix.com -
ard＠p850ug1.demon.co.uk -
jpdavis＠gorge.net -
pete＠dunnington.u-net.com