0

Pressure Sensor Over An Area
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

Pressure Sensor Over An Area

by ArthurBaranovskiy on Wed Jul 11, 2018 2:58 pm

Hello,

I am looking for a pressure sensor over a "grid", where it can identify how much pressure is applied and where exactly. For example, we currently have a 4" x 3" rectangle, with twelve 1x1" sensors. However, this is very poor resolution, only 12 pixels.

I would like a pressure pad of some sort, such as this one:

https://www.adafruit.com/product/1075?g ... dAQAvD_BwE

However, I would like to be able to identify where on the grid the pressure is applied. Eventually, this sensor will be used to map out pressure readings over the course of an experiment or trial. Any advice would be appreciated. Sensor dimensions have to be about 5" by 4". I'm willing to make this sensor out of several others, if needed. Meaning out of 4 strips laid side by side, or several smaller squares set up next to each other.

Thank you
Last edited by ArthurBaranovskiy on Wed Jul 11, 2018 3:01 pm, edited 1 time in total.

ArthurBaranovskiy
 
Posts: 5
Joined: Wed Jul 11, 2018 2:52 pm

Re: Pressure Sensor Over An Area

by adafruit_support_bill on Wed Jul 11, 2018 3:01 pm


adafruit_support_bill
 
Posts: 70401
Joined: Sat Feb 07, 2009 10:11 am

Re: Pressure Sensor Over An Area

by ArthurBaranovskiy on Wed Jul 11, 2018 3:04 pm

adafruit_support_bill wrote:Here is one option: https://www.adafruit.com/product/1676


Thank you! This is almost perfect. However, I think that the pressure's exerted will be slightly more than a touchscreen can handle. I always thought of touchscreens as being much more delicate, and sensitive to touches, as opposed to continuous pressure of 10-50 PSI. However, I am looking at the screen you just posted, and am looking at pressure specs.

Thank you again :)

ArthurBaranovskiy
 
Posts: 5
Joined: Wed Jul 11, 2018 2:52 pm

Re: Pressure Sensor Over An Area

by adafruit_support_bill on Wed Jul 11, 2018 3:12 pm

Resistive touch screens are different from capacitive. They work by pressure and some are more sensitive than others.

This white-paper from Cypress goes into the details of how you can get pressure and position data from them:
http://www.cypress.com/file/134996/download

adafruit_support_bill
 
Posts: 70401
Joined: Sat Feb 07, 2009 10:11 am

Re: Pressure Sensor Over An Area

by ArthurBaranovskiy on Wed Jul 11, 2018 4:09 pm

adafruit_support_bill wrote:Resistive touch screens are different from capacitive. They work by pressure and some are more sensitive than others.

This white-paper from Cypress goes into the details of how you can get pressure and position data from them:
http://www.cypress.com/file/134996/download


Thank you for that article! It was very informative,and now I know the difference between capacitive and resistive touch screens. However, I don't believe the article mentioned anything about pressure amounts. It isn't enough simply to know exactly where the pressure is applied, we need to know how much. This will allow us to create a "map" of how much pressure is exerted over the area. A touchscreen responds to touch. This will not work for this application. There will be something resting on the sensor at all times, an expanding pouch, we just need to know how much pressure it exerts, and where exactly.

Thank you

ArthurBaranovskiy
 
Posts: 5
Joined: Wed Jul 11, 2018 2:52 pm

Re: Pressure Sensor Over An Area

by ArthurBaranovskiy on Wed Jul 11, 2018 4:19 pm

adafruit_support_bill wrote:Resistive touch screens are different from capacitive. They work by pressure and some are more sensitive than others.

This white-paper from Cypress goes into the details of how you can get pressure and position data from them:
http://www.cypress.com/file/134996/download


https://www.sparkfun.com/products/9376

This is almost exactly what I'm looking for. However, this sensor doesn't have spatial awareness (I won't know WHERE the pressure is being exerted) and its not terribly accurate.

Therefore, I need a Force Sensitive Pressure Sensor like the one from Sparkfun, with an XY coordinate system for orientation purposes, like the touchscreen you showed me.

ArthurBaranovskiy
 
Posts: 5
Joined: Wed Jul 11, 2018 2:52 pm

Re: Pressure Sensor Over An Area

by adafruit_support_bill on Wed Jul 11, 2018 4:22 pm

However, I don't believe the article mentioned anything about pressure amounts.

It is on page 2:
Resistive Touchscreen Measurement
Method
A touch can be defined by three parameters. The first and
second parameters are X-position and Y-position. The third
parameter relates to “touch pressure”
and allows the
touchscreen to differentiate between finger and stylus
contacts.

. . .

Finally, to obtain the touch pressure, we take two
measurements of the cross-layer resistance. VCC is applied
to a conductive bar on one of the layers while a conductive
bar on the other layer is grounded. We measure the
voltages on the unconnected bars, shown in depictions c
and d in Figure 3


However, it can only give you an overall pressure measurement. It will not give you a 'pressure map' showing the pressure distribution over the sensor area.

There are lots of research projects and experimental sensors in development. But I do not know of any commercially available products that will do what you want.

adafruit_support_bill
 
Posts: 70401
Joined: Sat Feb 07, 2009 10:11 am

Re: Pressure Sensor Over An Area

by ArthurBaranovskiy on Wed Jul 11, 2018 4:33 pm

adafruit_support_bill wrote:
However, I don't believe the article mentioned anything about pressure amounts.

It is on page 2:
Resistive Touchscreen Measurement
Method
A touch can be defined by three parameters. The first and
second parameters are X-position and Y-position. The third
parameter relates to “touch pressure”
and allows the
touchscreen to differentiate between finger and stylus
contacts.

. . .

Finally, to obtain the touch pressure, we take two
measurements of the cross-layer resistance. VCC is applied
to a conductive bar on one of the layers while a conductive
bar on the other layer is grounded. We measure the
voltages on the unconnected bars, shown in depictions c
and d in Figure 3


However, it can only give you an overall pressure measurement. It will not give you a 'pressure map' showing the pressure distribution over the sensor area.

There are lots of research projects and experimental sensors in development. But I do not know of any commercially available products that will do what you want.


Thank you for your time. You answered my question!

ArthurBaranovskiy
 
Posts: 5
Joined: Wed Jul 11, 2018 2:52 pm

Please be positive and constructive with your questions and comments.