On Feb 21, 11:29*pm, "RogerN" wrote:
I'm wanting to make a display for load cells, good looking ones on eBay seem
to start around $150. *This is a bit hard to justify for tinkering around,
especially since the load cell I want also costs around $150. *As I
understand it, most digital scales work with some sort of strain gauge load
cells. *This leads to the idea of getting a cheap scale (bathroom, fishing
scale, food scale) for $20 or so and using the display and electronics to
read whatever load cell I want. *In order to do this I would need to be able
to recalibrate the scale. *I don't mind simple X10 or X100 display (example,
display shows 200 for 2000 or 20,000 lbs) but I don't want to need a
calculator to scale and offset the reading for units conversion.

Anyone here done anything like this? *Know of any cheapie scales that can be
recalibrated to different weights with other load cells? *If this isn't easy
to do I'll probably just get a load cell amplifier board and use the scale
and offset pots to get the reading on my voltmeter, maybe something like
1.000 Volts = 10,000 lbs or whatever depending on the load cell.

My most immediate use will be to tension the guy wires on the antenna tower
I'm preparing to put up and later hopefully to do tests on construction of a
homemade crane. *I'd like to verify/test my force calculations to keep the
design factor correct.

RogerN

Without a lot of messing about, you're kind of chasing your tail on
converting non-documented equipment. Me, I'd probably start with one
of the embedded microcontroller boards for dummies that uses Basic,
has A to D converters on board and display options. That's if you
want to get a job done. If you just want to fiddle-fart around with
something that'll be obsolete next week, hit the dollar store and pick
up a digital bathroom scale. I think you'll find the innards are
laser-trimmed and one giant blob with no pinouts. Since the model
you'll buy will never be seen again once the shipping container is
emptied, any work you put in on converting same won't ever apply to
anything else.

Raw strain gauges are what's used on a job like you want, epoxy them
on and measure the resistance change. Figure the strain from that.
They were doing that at John Deere 40 years back, before there were
any digital doodads. Cheap enough to be one-time use items.

If you just gotta have load cells, there are a number of surplus
outfits that have had various load ranges in the 10-20 buck range.

Stan