Light Pen Scanner vs. RS232

[Dean Landry]

Hello,

I recently purchased a scanner off ebay to read barcodes. Turns out it
is something called "Light Pen" instead of RS232. Does anyone know what
it's application is? I'm told by the manufacturer that it cannot read a
barcode and send the ASCII data to a PC. I'd love to find a way to make
this work If I can't, my friend who is building a robot might get an
early Christmas gift

Thanks,

Dean

 

There are a couple of different devices described under the name "light
pen" but it sounds like you have a dumb barcode scanner head, which has
a source of illumination (often an LED) and a phototransistor. The
output is simply the raw output of the phototransistor, which
fluctuates according to the albedo of whatever surface is under the
active area of the scan head.

You need to write a lot of realtime software to capture the incoming
baseband and decode it. You could do it all in a small microcontroller,
which could then give you the RS232 output you crave, but it is not at
all a plug-n-play sort of thing.

 

Wow. Interesting. Looks like this is a modern CCD/CMOS image sensor
type scanner that has been set up to emulate the old
LED+phototransistor arrangement. It would be useful with old terminals
that require the old type of dumb sensor. The advantage of this unit is
that it has consistent timing, unlike the dumb sensor which has
variable timing as you vary the swipe speed.
No you can't buy the micro you need off the shelf (TTBOMK).

 

[Jim Adney]

On Tue, 07 Dec 2004 15:11:44 GMT Dean Landry <dlandry@cs.dal.ca>
wrote:

Turns out it
is something called "Light Pen" instead of RS232. Does anyone know what
it's application is? I'm told by the manufacturer that it cannot read a
barcode and send the ASCII data to a PC.

Could it be one of the very old devices which were used to point to a
computer monitor screen and pick out a position on the screen by the
timing of the raster as it came past? These would have had only a
photo transistor in them, no light source.

Just a guess.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

If you search for the model and mfr you see that it's actually a narrow
shaver-style scan head, sold with several interface options, one of
which is RS232. Seems like this particular variant emulates the type of
dumb photoFET reader used to read barcodes e.g. in libraries. Weird
idea.

 

[Douglas Scot Gillman]

The forensic RL Polk is somewhere invloved with
a lady veterinarian out west.

The drag irons available should meet contrition
at the other end of the rainbow.


Dream on nacelles' wind, Caught in tepid Tome, an urge,
Gin in from the cold.

 

[Dean Landry]

larwe@larwe.com wrote:

There are a couple of different devices described under the name "light
pen" but it sounds like you have a dumb barcode scanner head, which has
a source of illumination (often an LED) and a phototransistor. The
output is simply the raw output of the phototransistor, which
fluctuates according to the albedo of whatever surface is under the
active area of the scan head.

You need to write a lot of realtime software to capture the incoming
baseband and decode it. You could do it all in a small microcontroller,
which could then give you the RS232 output you crave, but it is not at
all a plug-n-play sort of thing.

Is the microcontroller something that can be purchased? I can't figure
out what this particular scanner is useful for as-is. It is a
Metrologic MS951-15.