I have a hobby project that I am working on and I am trying to find a
bathroom-type scale that can hook up to a computer via serial port
and/or usb.  I would like to find one of each if I could.

The operation can be rather simple, a user steps on the scale and the
weight is transmitted over the wire.  Maybe some simple commands to
reset the scale.

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Request for Question Clarification by maniac-ga on 21 Feb 2005 19:44 PST

Hello Ericb01,

You mention this is a hobby project. What kind of price are you
looking for and/or how comfortable would you be at modifying hardware?

A scale with RS-232 (serial) interface runs about $800. This is
obviously a professional model, suitable for a medical office.

The alternative would be to use a load cell interface but this would
require some "hardware hacking" to put together.

Would an answer describing one (or both) of these solutions be OK? If
not, please describe the limits you are looking for.

  --Maniac

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Clarification of Question by ericb01-ga on 21 Feb 2005 20:43 PST

Hi Maniac,

As hobby project, I was definitely thinking $100-200 range.  $800 is
definitely out of the budget.  My solution would be a "plug-n-play"
type (USB/RS232).  No soldering or wiring necessary. I can tolerate
+/- 1 pound accuracy.

I'm not very comfortable doing hardware hacking so that would probably
not be an option either.

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Request for Question Clarification by maniac-ga on 22 Feb 2005 17:41 PST

Hello Ericb01,

Hmm. I did some more searching and a premade bathroom scale with a
computer interface is pretty rare and pretty high priced.

The best approach you may want to consider (yes - it requires some
wiring) is to purchase a load cell to USB interface like
  http://www.massload.com/computerweighing.html
(alas - no price available on line) which converts the load cell
output (found in a digital scale) to a USB interface. Some wiring /
calibration would be needed for this solution. If you have a friend
that has some electrical or electronics [preferred] experience, they
should be able to hook it up for you.

There appear to be several of these types of devices, try a search like
  "usb interface" "load cell"
for providers. The price of this kind of interface SHOULD be in the
range you quoted ($100 to $200) but I cannot tell for sure. A USB
mouse is available for a few dollars, but that has a custom chip /
high volume. I am aware of several USB 2.0 breadboard interfaces at
about $100 (much more expensive than USB 1.x), that is certainly a
possibility as well.

Good luck with your work. Another researcher may also have different
sources of information to help as well.

  --Maniac