"Stanley Schaefer" wrote in message
...

On Feb 21, 11:29 pm, "RogerN" wrote:
I'm wanting to make a display for load cells, good looking ones on eBay
seem
snip

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

I have a couple of Arduino boards and an AD7730? chip for weigh scales, it
has 24 bit A/D converter IIRC. I like this idea because I can save
calibration for different load cells to eeprom. So I could use the same
Arduino scale display for a reloading scale, plug in a different load cell
and have a 10,000 lb crane scale. Arduino already has a built in function
to scale and offset readings. The down side of this is I need to get it all
mounted in a case and set up for battery operation for the crane scale duty,
not too bad though.

I found some big game scales online in the $30 range for 300lb digital or
440 pound dial, I will probably get one of those for tensioning my guy wires
for the antenna tower. According to the rules of thumb for my 1/8" wire
rope I need to tension the guy wires to 170lbs.

I saw some videos on youtube of calibrating some of the chinese scales, some
let you specify the weight you are calibrating at, not sure how well it
would work with a different load cell and a much larger full scale number.

RogerN