hi,
i am looking to hopefully develop and idea into a tangible demo.
i am looking for a part which I dont know the proper name for.

I am looking for a pot or a small device that would give a resistance (preferable) or a voltage as it is pulled. i am looking some somehing that can handle anywhere from 50 to 200lbs.

i guess this should be a comercially availalbe part as probably all of the digital hanging scales should use something similar.

it would be ideal if the part:
was spring loaded - or returned to its resting place when no force was applied to it.
should be able to handle a dead weight of min 50lbs would. be nice it it. was 100lbs
if it has an "in-line" design it would be better

thanks for the help

 

A load cell?

 

A load cell?

I looked at load cells but from what I can see they record push weight sort of like a traditional scale, I a, looking for something that records pull force.

ill look again into load cells

 

Look for tension load cell.

 

Take a look at these guys:

https://www.transducertechniques.com/

They're good quality (though not as cheap as Chineese) products, and are made in the U.S.

 

There are also curvature sensors that can be set up to measure deflection of a rod, for instance, if you want to measure a force applied to the rod.

But yes, all you need is a tension load cell.

If it was me, I'd get a cheap bathroom scale and hang a harness off of it, so that a pull on the harness appears as weight on the scale. That's how we used to weigh our giant pumpkins back home. They're too big and awkward to place on a scale directly.

 

You might also consider a simple spring and an LVDT. If you are handy, you could even wind one yourself.

 

You might also consider a simple spring and an LVDT. If you are handy, you could even wind one yourself.

You could also have a spring and a length of rope going round a pulley connect to a pot as a DIY version, but OP wants off the shelf.

 

Interesting concept. If I wanted to do this I'd go to my bag of tricks (Junk box) and grab one of those sliding pots I scrapped out of an old treadmill. Put a light spring to return it to the zero point and use a small cable to connect it to the end of a spring that was rated to handle the weight load you want. Of course it would be everything BUT calibrated, and I don't know if spring tension is linear or logarithmic, but it would be an interesting learning process.

Use the slider pot as a voltage divider and use an Op-Amp to tailor the output.

Well, that's what I think I'd do if I wanted to do what you propose. Like I said, not "Accurate" but if you merely want a reference or comparison it should be fairly meaningful.

Oh, and those sliding pots from a treadmill, they're about 3 inches long, so it should allow you to have some sort of useful range - depending on the spring holding up the load.