Capacitive smart surface questions

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Anonymous
Not applicable

Hi,

   

I am building a device that allows objects to be recognized on a smart surface. We decided to stick with capacitive sensing.
See this for an example: https://www.tiggly.com/
The final design will be a modified version of the Magic Trackpad. https://www.ifixit.com/Teardown/Magic+Trackpad+Teardown/3395
It consists of a few blocks:
Sensor for Touch (10", 10 points) -> Controller -> Raspberrypi(outputs processed data - OBJ_ID at (X,Y) )+BT -> Tablet-> Application

   

 

   

I have a few questions:

   

-Is it realistic finish integrating the Controller and Digitizer into a working prototype in 1-2 months? I am a bachelor electronic engineering student
There is an option of buying a development kit with a screen or ready products but this is not really designing. Even with this option there is a lot of work to be done still, so i am worried about the timeline.
devkit: http://nl.farnell.com/microchip/dv102013/dev-brd-mtch6303-capacitive-multi/dp/2500452
example of controller: http://www.farnell.com/datasheets/1948343.pdf
example of Digitizer: http://www.ebay.de/itm/DIGITIZER-iPad-2-SCHWARZ-Touchscreen-Front-Glas-Touch-Frontscheibe-Display-LC...

   

-Do you know of Capacitive Touch controllers that are able to process Z-axis data/proximity/hover as well, and output a diameter of the touch or distance from the surface? I need this in order to differentiate between merely taking your hand off the object, and taking the object off the surface. Other ways of sensing this difference are welcome.

   

I am waiting for the Cypress datasheets.

   

- I am having difficulties with finding capacitive digitizer manufacturers that have them readily available at a good price:
http://nl.rs-online.com/web/p/touch-screen-sensors/7496849/ vs http://www.ebay.de/itm/DIGITIZER-iPad-2-SCHWARZ-Touchscreen-Front-Glas-Touch-Frontscheibe-Display-LC...
Where should i seek these screens? I found 3M, AMT, DMC but they are a lot more expensive than digitizers.

1 Solution
Yuva
Moderator
Moderator
Moderator
250 replies posted 250 sign-ins 100 solutions authored

Hi,

   

Welcome to Cypress Forum. We have trackpad design with self  cap (CSD), but with this multi-touch is not possible. For multi-touch mutual cap (CSX) is required. We have CSX for keypad and are currently developing this for trackpad. You may choose the one suitable for you.

   

You may refer to the following details

   

1. Kit -> http://www.cypress.com/documentation/development-kitsboards/cy8ckit-040-psoc-4000-pioneer-developmen...

   

2. Controller -> http://www.cypress.com/documentation/datasheets/psoc-4-psoc-4000-family-datasheet-programmable-syste...

   

You can also do the proximity sensing using this device. Refer to the following application note for details of using proximity.

   

http://www.cypress.com/documentation/application-notes/an92239-proximity-sensing-capsense

   

We don't have any details about the ITO screen (digitizer). You may have to contact third party vendor for this.

   

Regards,

   

Yuva.

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4 Replies
Yuva
Moderator
Moderator
Moderator
250 replies posted 250 sign-ins 100 solutions authored

Hi,

   

Welcome to Cypress Forum. We have trackpad design with self  cap (CSD), but with this multi-touch is not possible. For multi-touch mutual cap (CSX) is required. We have CSX for keypad and are currently developing this for trackpad. You may choose the one suitable for you.

   

You may refer to the following details

   

1. Kit -> http://www.cypress.com/documentation/development-kitsboards/cy8ckit-040-psoc-4000-pioneer-developmen...

   

2. Controller -> http://www.cypress.com/documentation/datasheets/psoc-4-psoc-4000-family-datasheet-programmable-syste...

   

You can also do the proximity sensing using this device. Refer to the following application note for details of using proximity.

   

http://www.cypress.com/documentation/application-notes/an92239-proximity-sensing-capsense

   

We don't have any details about the ITO screen (digitizer). You may have to contact third party vendor for this.

   

Regards,

   

Yuva.

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Anonymous
Not applicable

Currently, i am trying to see if using an off-the-shelve touch sensor, which outputs coordinates will be enough. Example: http://nl.rs-online.com/web/p/touch-screen-sensors/8186795/

   

In case i have to delve deeper into Z-axis or diameter of the touch, i will be integrating a controller with a sensor by myself. Example: http://www.microchip.com/design-centers/touch-input-sensing/gestic-technology/getting-started

   

How much time do you estimate that the integration of Plan B will take?

   

To go back to the objects, assume i have no access to Z-data or the diameter of the touch, thus i don't know if the object is approaching or departing. I only have binary: on/off state.

   

I have the issue of not being able to tell the difference between an object being off the surface, and it simply not having a human hand touching it. False state problem.

   

Therefore, i came up with the solution to make the object totally active. This can be done with either:

   
        
  • internal power and circuit; How does this work? http://www.frequency.com/video/arduino-plays-timberman-faster/183328492
  •     
  • external power and circuit (wireless charging)
  •     
  • attach a long wire, making the object capacitive itself. 10cm was enough for me. Why does this happen?
  •     
  • connect objects to ground. perhaps with a layer of conductive foil that is grounded on top of the sensor. this layer connects to the objects through the feet. But here my EMF knowledge stops and i need to experiment.
  •    
   

But this brings up the issue of only having 10 touch points, so very limited nr of objects simultaneously. I attempted to solve it in the following ways:

   
        
  1. Make the object switch: capacitive/non-capacitive/capacitive with a frequency determined by me. This eliminates the limit of object nr imposed by 10 touch points. See this paper for morehttp://www.cs.nccu.edu.tw/~jonesyu/papers/paper206_yu_v6.pdf
  2.     
  3. Make the object active only for 5 seconds after the human touches it. This eliminates the limits of object nr due to 10 touch points. But still lets us see a correct state change.
  4.     
  5. Fuse sensors in order to use one sensor underneath the touch that can tell me if the object is on the surface or not. If i use magnetism, i might have interference.
  6.    
   

So i am wondering if you knew of other ways to solve that problem, and if you know of ways to accomplish those 3 solutions.

   

 

   

I am currently research Wacom and more fundamental physics to understand what is happening. http://www.androidauthority.com/break-it-down-how-does-the-s-pen-work-154435/

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Anonymous
Not applicable

If i make the objects passive, so that they have their feet seen only upon touch, then i have a challenge.

   

I need to be able to differentiate between a false state change (touching the object) and placing or removing the object from the surface.

   

So for this i thought of a few solutions:

   

Z data (1cm is sufficient) of the object feet for data analysis. Hard to do but reliable to know if the object is approaching or departing. Do you know of any such chips? http://fastpokemap.us/download-fastpokemap/
Hand recognition, as the Gestic system is able to do. This tells me if the user moved his hand in a certain way, still error-prone.
Merge with magnetic switches below, adding one more sensing ability to the surface. but this interferes with the e-Field?
Some kind of timer in the object. So that it stays active for a while after touched. Following the count down you can know if it was left on the surface. 

   

I am reading into the physics fundamentals now.

   

Any other ideas? https://apps2apk.in/download-latest-free-4shared/

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Anonymous
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