tips to solve a problem (singular)

Hi guys. I need help! :confused: I have to realize in the simplest possible way,a touch system. I have to create needs to be flexible, simple, and not expensive

in practice I have to build a strip able to understand where I'm touching to me it just measures the x-axis.

I do not think such a thing exists in the market. (for the length of the object to be create and for the shapes)

for now my idea was:

1) put two parallel conducting strips (they do not touch each other) 2) connect to each strip a pin of Arduino 3) when the finger is pressed on both strips it closes the circuit 4) calculate the impedance of the circuit and calculate X-Axis

I have tried with A0(AnalogRead) + 13(DigitalWrite HIGH) but the problem is that: the finger has a high resistance and makes difficult the trick.

I read that Arduino might already have some library can do to my case: Capacitive Sensing Library

or better to use something like this? TLC555

I hope someone has some advice for me :'(

I would start with the Capacitive Sensing Library. I can not see any application for a timer here, if your TLC555 is a different beast, please provide a link.

Your hope to get any usable x-position by your one sensor setup is too optimistic IMHO.

Here you go: https://www.sparkfun.com/products/8679

It exists; there's several different sizes available.

You can even go force-sensitive (no, not The Force) to measure pressure instead of position.

I feel like I've also seen capacitive sensing strips that tell you position, even without having to apply pressure to it. Not sure where though....

MorganS: Here you go: https://www.sparkfun.com/products/8679

It exists; there's several different sizes available.

You can even go force-sensitive (no, not The Force) to measure pressure instead of position.

great! But I am unfortunate because I can not use it. the structure on which I have to work is non-linear, almost like a "S" but very interesting..

Whandall: I would start with the Capacitive Sensing Library. I can not see any application for a timer here, if your TLC555 is a different beast, please provide a link.

Your hope to get any usable x-position by your one sensor setup is too optimistic IMHO.

TLC555 It is a component of this object: http://makezine.com/projects/drawdio-musical-pencil/ the project when changing resistance changes the sound, I would do a variant. I admit that I do not have perfect knowledge to easily understand the system

I tried the Capacitive Sensing Library, what I can do now is very similar to creating a button, but from here to be able to have a value on the X axis, I need to improve my knowledge. some advice?

if I need anything is not an issue.. for now I prefer some simplification thanks to some hardware. :)

A non-linear X-axis? That's a new one.

Tappo: the project when changing resistance changes the sound, I would do a variant.

With what resistance? BTW. the 'music system' does not use any spatial information.

MorganS:
A non-linear X-axis? That’s a new one.


It is not for a scientific application.
then I am ready to find some inaccuracies of scale

Whandall:
With what resistance? BTW. the ‘music system’ does not use any spatial information.

reminding me that he had seen this object, I thought that under appropriate changes could do to my case

it has a sound change according to the distance between hand and pen.
Taking it all as input I can mathematically work with Arduino and calculate the distance.
(of course it is very approximated and varies with the surface)

Tappo: it has a sound change according to the distance between hand and pen.

As far as I understood it changes the sound according to the resistance of your hand shorting some wires. No touch, no sound.

Whandall:
As far as I understood it changes the sound according to the resistance of your hand shorting some wires. No touch, no sound.

yes yes I have tried to simplify the explanation…

you say that we can read this value also in Arduino?
if even with this TLC555…

But the resistance varies with pressure, moisture, calluses, etc.

How about a series of fingers on a PCB? Each one is connected separately. Placed apart so that your finger covers 3 of them at a time. Using capacitance to sense whether or not your finger is there, and placing it either at the trace with the most capacitance, or weighted to get in-between values.

That's how I do this kind of thing.

Note: you are NOT using resistance. There should be an insulating layer between your finger and the traces.

polymorph: But the resistance varies with pressure, moisture, calluses, etc.

the effect varies person to person and from an infinity of events but I would love to test this solution.. but first I have to full understand the system

polymorph: How about a series of fingers on a PCB? Each one is connected separately. Placed apart so that your finger covers 3 of them at a time. Using capacitance to sense whether or not your finger is there, and placing it either at the trace with the most capacitance, or weighted to get in-between values.

thanks for the advice.. the surface to be covered is at least one meter .. too much work for the Finger

Why was this important dimension not included in the first request for help?

Agreed. Why not say at the start?

What kind of resolution? What do you mean "too much work for the Finger"? What kind of resolution? What is this for?

You can't just put your finger across two parallel strips of copper and "calculate the resistance". Your finger is a major part of the resistance, the copper nearly nothing at all. So even slight changes in finger contact resistance make this an impossible task.

Tell us what you are doing, how large it is, what kind of resolution and speed this requires.