I'm curious about which device I can use, as well as how to code it, to measure the change in capacitance that occurs when pressing copper tape with a polymer insulator in between. Ultimately, I want to arrange the lines in a 2x2 grid so that when pressure is applied at an intersection, I can detect exactly where it’s happening. The goal is to use this detection as a remote control mechanism to operate an RC car.
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You said capacitive, but I think you are referring to touch pins.
Check the Hardware section on this site and start looking at the board specs to see if it supports touch sensor. I would start with the NANO.
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I'm not sure what is your goal.
First, you mean pressure from a finger? Or what else?
Next, if you talk about a "capacitive" sensor, please note it won't be triggered by pressure, but capacitance changes (i.e. you don't need two copper layers to do that, you just need 4 separate "pads").
If you really mean to be able to detect a pressure (either with a finger or a stick) over a sensor, it is usually made by a variable resistance layer, aka " Velostat".
But if you just need 4 detecion points why not using 4 already-made pressure sensors (and relative connection/driver and code)?
Just as an example:
If this can't help you, I thin you better give us more details about the project and/or requirements...
PS: if you post on "Arduino UNO R3" forum, you assume you already think to use such device.. 
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That is possible but requires a lot of custom electronics.
You might consider two of these sliders
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Hello. I want to differentiate between a simple touch and actual pressure so that the sensor only activates when the applied force exceeds a certain threshold. Rather than merely measuring the capacitive changes due to a finger’s proximity, I’m interested in monitoring how the dielectric properties of the polymer insulator change under pressure. Therefore, I believe placing electrodes both above and below the insulator is the correct approach.
While using a film pressure sensor like Velostat is one option, my goal is to directly measure how the polymer’s dielectric constant changes with pressure, ensuring that the sensor only responds above a certain (critical) pressure. This way, light touches or minor contacts won’t trigger the sensor, and it will only activate when a more substantial force is applied.
Hence, I’d like to know if it’s feasible to detect pressure by placing electrodes on both sides of the polymer and monitoring the change in capacitance. Also, I’d appreciate any advice on which Arduino device or sensing circuit would work best for this method, as well as any libraries or example code I might reference.
Really thank for your advice!
Thank you for the advice! I understand that a lot of custom electronics will be required. However, I’m aiming to detect force above a certain threshold rather than just simple touch, so I’m exploring methods for measuring changes in a polymer’s dielectric properties under pressure rather than using a capacitive slider sensor.
Specifically, I plan to place electrodes above and below an insulator and measure the resulting change in capacitance as pressure is applied. I’m looking for any recommendations on the circuitry or sensor modules needed for this, as well as any relevant resources or examples. If you have any ideas or prior experience, I would appreciate hearing about them!
Too technical for me and outside my experience so I will bow out.
Hello,
I am currently arranging a 2x2 grid of copper electrodes to detect pressure at each intersection by measuring how the polymer’s thickness changes under force, which in turn affects its capacitance. My goal is to identify which of the four points—(0,0), (0,1), (1,0), or (1,1)—is being pressed.
I have tried using a touch sensor like the MPR121, but it seems to be optimized for touch detection rather than measuring the capacitance changes caused by actual pressure (i.e., changes in the polymer’s thickness). Ideally, I’d like to distinguish between simple touch-based capacitive changes and the true pressure-induced changes in the polymer.
If you have any suggestions for the appropriate electronics, sensor modules, or reference materials to facilitate measuring pressure-induced capacitance changes in this setup, I would greatly appreciate your advice.
Thank you!
It is not clear what you actually want to do, but force sensitive resistors are popular for pressure sensing applications. FSRs are not useful for accurate measurements of pressure, force or weight.
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I have merged your cross-posts @dabin_shin.
Cross-posting is against the Arduino forum rules. The reason is that duplicate posts can waste the time of the people trying to help. Someone might spend a lot of time investigating and writing a detailed answer on one topic, without knowing that someone else already did the same in the other topic.
Repeated cross-posting can result in a suspension from the forum.
In the future, please only create one topic for each distinct subject matter. This is basic forum etiquette, as explained in the "How to get the best out of this forum" guide. It contains a lot of other useful information. Please read it.
Thanks in advance for your cooperation.
I think you can do what you want with the MPR121 by modifying the Adafruit library.
If that's not possible and you never mind spending time learning, the UNO R4, which is equipped with a Capacitive Touch Sensing Unit (CTSU), is one option.
I'd introduce you to this thread:
In the video at post #34 in the thread, a touch electrode configured as shown in the following picture is used to read the capacitance between the finger and the copper electrode in an analog manner to control the servo position.
The Renesas support page has detailed documentations about the CTSU for the UNO R4, i.e. Renesas RA4M1, so you can learn about it.
Ok, so IMO my advise is to use Velostat, so its resistance will be used to determine the applied pressure, and the code will do the job setting a trigger level to the required applied force.
If for any reason you need to use that polymer/capacitance approach, I'm sorry but I can't help you more because I have never had experience with such kind of sensors.
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