HP-41 Wand: scanning from monitor?


Do you think the HP-41 wand scans a bar code from a monitor instead from paper? It's just an idea. If the idea promises some success I would try to modify the user code compiler to output the bar code in a window.



I'm almost certain that it won't work, but you can check it on
http://rwiker.github.com/hp41barcode/ .


I am very certain that it will not work on a CRT monitor, however it may work on a LCD Monitor since many bar code scanners have been able to read successfully from LCD monitors or from mobile LCD devices.


It's about an LCD only.

Right now I do not have a wand (that's why I'm asking). If the chance is high that it works I'd try to get one.



Michael, I would like to support your efforts. I can loan you my HP-41 barcode reader wand or can do some testing for you using specific bar codes on LCD PC monitors that I have. You can also send me an e-mail to discuss this further if you would like. Regards.


I'll try again a response...

I really appriate your offer. I live in Germany and it is very expensive to ship a package from the US to Germany and back. For the first steps it would be very helpful if you could do some tests for me (when I have something testable).

Thx a lot!


Didn't work for me - LCD monitor, different scale sizes, to not avail. Just one data point, by all means you go ahead and try as well.


Probably those barcode scanners which read successfully from LCD monitors/screens are using a camera and doing image processing.

IIRC the 41c wand is a simple phototransistor or photodiode set up to sense reflected light (white space) or its absence (the bars). I suspect that this design would not be happy with the flickering light emitted from a CRT or even the higher-frequency flickering light from the LCD backlight (either cold-cathode fluorescent or PWM LEDs).

But it might work... And perhaps could be modified to work.

It might be easier to start with a new approach. For example, two photodiodes could be aligned to two areas on the display and those areas could alternate light and dark. One could be a clock, the other data. Then the higher-frequency noise could be ignored because the clock would give the frequency of interest and the data could be checked in sync with the clock. (Think a one way optical I2C or SPI.)


Or maybe connect a red LED to the PC and control it in the right sequence while holding the wand over it?


Hi all,

The LED pointing to a Wand tip approach (or the other way around if you prefer) certainly works. I tested it a few years ago and managed to simulate some keyboard entries from the Wand.

Just the Wand switch must remain pressed along the whole transmission process.

Also have doubts that CRT or LCD screens can do the job... (too flickery IMHO) but it's just a hobby, so better give it a try and let us know! ;-)

Cheers from Caribbean Sea.



ho ho this brings back old memories.

it was back in 1983 or 1984 when I was trying to see how to get data into my HP-41C without actually typing it in when I investigated using the Wand as an input device (without going through the process of printing the barcode and scanning it manually).

So I used Blue Tac to anchor my wand over the "CAPS LOCK" LED on my BBC microcomputer and then wrote a program to flash the LED simulating various types of barcode. I remember being able to download entire programs, compiled using modified versions of the programs included in the HP Book "Creating your own Barcode" (available on the MoHPC DVD).

The Blue Tac also prevented stray light from confusing the sensor.

The only problem was that I had to press the key on the wand before sending each bar code.

I then came across the data sheet of the
HEDS-3000 Wand
(a version of the Wand designed for connection to other computers) and realized that the HP-41 Wand was a HEDS-3000 connected to the special connector with the ROM and interface.
(more info on the HEDS-3000 are in the Jan.1981 HP Journal)

So I disassembled the connector and disconnected the cable. I then added connectors to both ends so that I could use the Wand as before.

Alternatively I could disconnect the interface connector and connect the Wand cable to the user port of the BBC (essentially a parallel port) and use the Wand as an input device of my BBC (I remember writing a program to read some barcode from BYTE magazine in HP-41 format). I also used the Wand to read BBC programs distributed in barcode format by the BBC-User magazine.

I also connected the interface connector of the Wand to the BBC so that I could use the BBC to send data and programs to the HP-41. I do not recall actually doing anything with that. It could be because I didn't have the time or I somehow was too scared to connect my precious HP-41C directly to another computer ( I remember the HEDS data sheet suggested using a transient voltage suppression device - Transzorb - between the HEDS and the computer and I didn't have these parts at the time).


Edited: 16 Feb 2012, 10:52 a.m.

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