Is there any sensor that detect a pulling? I would like to connect a sensor to a string of fabric and get a continuous data from it. Something similar to a force sensitive resistor but instead of force applying to the sensor , a pulling is applied
Thanks
We need a more information.
Draw a diagram showing the components and mechanical bits and pieces.
Not sure. You can take a look at String Tension Tester: https://www.vernier.com/experiment/ep-ev3-4_string-tension-tester/
The idea is that the ardunino will be attached on a banister of a third floor building and 5 strings of fabric will be hang from it to the ground (around 10 meter longs)
at the end of those fabrics, just above the ground (in a height an average men can rich with is hand) a sensor will be attached to the fabric to detect when a person is pulling the fabric and the amount of force is applied.
the pulling of the fabrics (and the sensor attached to them) will in return play audio files and control the amplitude of those files.
You need to tell how the fabric is attached to something, so that something can move a bit and your sensor can detect the slight movement(force).
the sensor should be attached to the fabric - meaning the fabric will be wrapped the sensor.
a 10 meter 24AWG will be attached to the sensor and the fabric will be wrapped around that cable and the sensor.
is something like this could work?
If you want to measure the force, then you need a loadcell.
In the Netherlands we have a special word "unster" or "veerunster" for a device with a hook that can measure how much kilograms are hanging on the hook. For example to weigh a bag of flower in a windmill. In English it is called a spring scale.
If you buy a cheap electronic spring scale on Aliexpress/Amazon, then you will find a loadcell inside. It is cheap and accurate.
Pulling or pushing are both okay for a loadcell, but a pulling force to the opposite part of the fork turns into a pushing force.
Can you draw a picture with the fabric and the measurement device ?
Usually, a load cell as used in a weight sensor is used to detect a pulling or pushing force. That may be more precision/cost than you need though.
Something that may work in this application is a String Potentiometer. Basically it consists of a rotary potentiometer with a spring that will return it to the zero point. A string is wrapped around the shaft somehow and when the string is pulled, the resistance of the potentiometer changes. That resistance can be measured with an arduino. The nice thing about this approach is that it can be low cost and the size is limited mainly by how large a potentiometer you use.
What is the maximum force needed to measure?
Why not use a linear pot with a spring in parallel with it .
When you pull the fabric the spring extends and the pot moves
I would put a load-cell sensor at the TOP of the fabric. No need to run wires the length of the fabric.
If you just need pull/not pull indicating:
One limit switch per fabric.
Pull fabric, switch closes.
IME, linear pots are much noisier and less accurate than rotary ones. Also, they can be hard to find in linear taper: log taper is much more common.
Search "S type load cell".
properly called a Cable-Extension Position Transducer. more commonly called a yo-yo gage. not cheap. basically a janitors cable key ring with a potentioneter attached
Put something like this on a fixed mount, place a bar on the platform, suspend the fabric from the bar.
Forget load cells and knit your own sensor. In this project I used a Kitting Nancy to make a length of French knitting into a pull sensor. I used a normal thread along with conductive threads and elastic threads to make this.
Published
in The MagPi magazine No. 72 August 2018. Free PDF download of this issue is available.
I called the project Stretch Armstrong, after the TV presenter, classic music DJ and singer, Alexander Armstrong, whose picture you see being stretchered.
This look great! Can you elaborate on what I'm seeing? you connected two alligator clips to the two sides of the knitting? what is exactly or how is the sensor is reading the data from the two sides of the knitting?
I need more then pull/not pull indicating.
I need also detect that a pulling is accrue to trigger an audio file but also to have a continuous data from the pulling to control other parameters in the audio file (for the moment the volume of the audio file)
You can use a simple microswitch or reed switch and magnet to detect movement; and a spring to convert the pull force to movement.
