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capsense slider using concentric circles | Cypress Semiconductor

capsense slider using concentric circles

Summary: 1 Reply, Latest post by bhwj on 27 Oct 2014 10:58 AM PDT
Verified Answers: 0
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arjan66's picture
1 post

Hi all,

I want to create a single capsense button which is only activated if the button is pressed in the middle.
I want to rule out a button press in case of wiping over the button (unintentional activation).

My idea is to create a slider which exists of concentric circles to detect a movement over the button using the 'centroid' value calculated by the processor (CY8C41xx series)
I have created the design below:

The circles are made of ITO on a foil. The foil ends in a 6mm wide tail with 5 contacts to use in combination with  an omron PCB connector.

The blue and green circles are used as slider segments for detection. The brown circle at the outside is used as shield electrode.

The segment in the middle is 10.3mm wide (approx. the size of a fingertip). The distance between the segments is 0.5mm. The total foil is 28x28 mm (brown segment without tail) The tail is 12mm long

The area of the 4 segements have about the same size.

Does anyone has experience with implementing sliders and if this idea of mine can be functional?
The capacitive foil will be covered with a 3mm thick acrylic overlay.

I am looking forward to your reply/comments/improvements/recommendations!


bhwj's picture
Cypress Employee
25 posts

Hello Arjan,

The method which you have suggested seems complicated. For your used case (where you want to reject wipe on the sensor) you can use simple menthod to detect swipes. In this method you use a guard sensor (see attached figure) around your button to detect swipes. The guard sensor can be placed at a distance of 2mm from the button sensor and the guard sensor will be triggered only when there is a swipe on the touch surface. If the guard sensor is triggered (when there is a swipe), you can reject the touch status of the button.

The method you suggested also works. I believe you are detecting the centroid variation to detect touch. In your case you will be using 2 more sensor and this will increase your power consumption when compared to the previous method.





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