Tension Sensor Selection

Hi everyone! I’m very new to arduino and have a question that someone here may be able to help with.

I study mechanical engineering and am working on a project. I’ve run into the following issue that I think someone on this sub might be able to help with:

A very thin wire (similar to fishing line) will be unwinding from a spindle in my system through use of a pull force on one end and a stepper motor on the spindle itself. Throughout this process, I will need to measure the tension on the wire continuously.

I know a tiny bit about load cells from my instrumentation design course and I know this is the route I should probably take. My dilemma is that I don’t know where to start with sensor selection or system integration with arduino. I have found a few tension sensors online that come with a load cell mounted to a few small pulleys/wheels that the wire can guide through, but they are way outside of my budget and most are too large for my application.

Has anyone worked with something similar using Arduino in the past? Any advice, would be greatly appreciated! In the meantime, the research continues.

"Measure tension on a unwinding wire" is a hopelessly vague description of the problem.

Why not post a diagram of the mechanical arrangement, with some ideas about where and how the "tension" is to be measured?

I'd just buy a load cell and HX711 breakout board. You can get them very cheap on eBay or Aliexpress. The load cells are available in a variety of load ratings so you should pick the one which is suitable for your application. You just need to rig something up to attach the line to the load cell. You can get a suitable pulley on eBay/Aliexpress and the hardware to mount it to the load cell. They come with mounting holes, or you can drill other holes if you like. You just need to avoid drilling through the wires of the sensor part of the load cell, but it's obvious where that is and there's plenty of metal to work with away from the wires..

There is a HX711 Arduino library that will make it very easy to work with your load cell.

Remember you don't have to measure the tension on the line itself. Action = Reaction. So you can measure the tension on the hold-down bolts on the motor+gearbox and get the line tension from that, minus of course the weight of the motor and gearbox.

Sparkfun sells a nice S-shaped tension device that's good up to 200kg and gets resolution down to better than 1 gram using their HX711 breakout. It's too large and heavy for mounting on the end of fishing line, so it's best to screw that down to the mount and screw the motor on top of it. (Or bottom, we don't know which direction you're pulling.)