In proximity sensing, can sensors with shielded electrodes be made of flexible materials?

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user_4653071
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I used Cy8CKIT-040 and Cy8CKIT-024 for proximity induction, but since 024 is a hard PCB, I now want to make the sensor (including the shielded electrode) a flexible material so that it can be used in more applications.

Is this idea feasible?

Are there any other ways besides using FPC, a flexible circuit board?

best regards!

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1 Solution

I think I misunderstood your previous explanation.

You can implement the proximity sensor on a flex PCB (top layer) and shield electrode in the bottom layer. The shield electrode in the bottom layer will help in reducing the cp of the proximity sensor (thereby increasing distance) as well reduce the effect of grounded objects.

We have a similar design that implements prox sensor and shield electrode in a flex PCB.

https://www.cypress.com/documentation/development-kitsboards/cy8ckit-041-41xx-psoc-4100s-capsense-pi... . Download the design files and look for the flex PCB layout.

CY8CKIT-041-41XX Design Files.zip

Regards,

Bragadeesh

Regards,
Bragadeesh

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22 Replies
VenkataD_41
Moderator
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750 replies posted 500 replies posted 250 solutions authored

Hi,

Yes. You can make flexible proximity sensors. Please note that in case of flexible sensors do not use hatched ground just underneath the proximity sensors. Otherwise the parasitic capacitance of the sensors will be high (since the distance between the sensors and the ground hatch is less in case of flex PCB).

You can also use ITO material on flexible films to design proximity sensors. Please refer page number 90 secton 3.8.16 of the following application note:

https://www.cypress.com/file/41076/download

Also, please note that you neeed to make 3-4 designs and each design should be manually tuned to optimize the performance.

Hope this information helps !

Thanks

Ganesh

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thank u for ur response!

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Is that to say shield electrode cannot work when I wanna use a FPC?is it right?

well,is it possible to use flexible electrode materials(like flex PCB) and shielded electrodes at the same time?i have to use a shield electrode because i need to achieve a long proximity-distance.

best regards!

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Is that to say shield electrode cannot work when I wanna use a FPC?is it right?

No. Shield will work with FPC. Infact we recommend you to use hatched shield instead of hatched ground underneath the CapSense sensors.

well,is it possible to use flexible electrode materials(like flex PCB) and shielded electrodes at the same time?i have to use a shield electrode because i need to achieve a long proximity-distance.

Yes. You can use shield with Flex PCBs.

Thanks

Ganesh

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okay.thank u!

is flex PCB with shield  better or worse than PCB with shield (just as CY8CKIT-024) in terms  of  achieving large distance?

in addition,other than the flex PCB, are there any other materials that can be used to make flexible electrodes  with shield electrode?

for example,ITO on flexible films u mentioned above?

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is flex PCB with shield  better or worse than PCB with shield (just as CY8CKIT-024) in terms  of  achieving large distance?

In short the difference is minimal. Suppose if you design a similar size and shape of sensors with flex PCB and standard PCB, the flex PCB works slightly better in terms of shielding since shield hatch is closer to the sensors.

in addition,other than the flex PCB, are there any other materials that can be used to make flexible electrodes  with shield electrode?

for example,ITO on flexible films u mentioned above?

You can use any material which is insulator and put sensors on them. You can even use no material which is a simple wire with air as the insulated material.

Thanks

Ganesh

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In short the difference is minimal. Suppose if you design a similar size and shape of sensors with flex PCB and standard PCB, the flex PCB works slightly better in terms of shielding since shield hatch is closer to the sensors.

well,if i use FPCB,these guidelines for standard PCB  are also suitable for FPCB?

pastedImage_4.png

You can use any material which is insulator and put sensors on them.

in general,the sensor and shield are copper or ITO, both the 2 material are hard.so ,just put the sensor wire loop and shield pattern/electrode on top of a flexible insulator?it can be flexible?

You can even use no material which is a simple wire with air as the insulated material.

i need a shield electrode/hatch pattern,but a simple wire cannot meet the requirement ,isn't it?

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Hi,

1. well,if i use FPCB,these guidelines for standard PCB  are also suitable for FPCB?

Yes, all these guidelines still apply.

2. First we would like to understand the application/ design to suggest you the best pattern. Please provide us images of your application/ design for better understanding.

We do not want the proximity sensor to move if that is what you are asking for. To make it around any curved surface, flex is suited. But still it should be fixed and should not move. Please explain the application to us.

Regards,

Bragadeesh

Regards,
Bragadeesh
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thanks!

We do not want the proximity sensor to move if that is what you are asking for. To make it around any curved surface, flex is suited. But still it should be fixed and should not move. Please explain the application to us.

Does that mean the sensor can't be applied to moving objects?can u explain why ?

***************************

I wanna design a sensor which could achieve 25cm-proximity-sensing distance and i hope the sensor can be applied to curved objects. and even I've thought about using this sensor on mobile robots to help them perceive objects

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Hi,

You may not be able to perceive the objects using proximity sensor. Proximity sensor is intended to be used to detect conductive grounded objects from a distance. Would you be able to share a video of your target application?

Regards,

Bragadeesh

Regards,
Bragadeesh
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yeah,i know that.I can make the target detector be a ground conductor.Is that possible?

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pastedImage_0.png

The general effect is something like this

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I think I misunderstood your previous explanation.

You can implement the proximity sensor on a flex PCB (top layer) and shield electrode in the bottom layer. The shield electrode in the bottom layer will help in reducing the cp of the proximity sensor (thereby increasing distance) as well reduce the effect of grounded objects.

We have a similar design that implements prox sensor and shield electrode in a flex PCB.

https://www.cypress.com/documentation/development-kitsboards/cy8ckit-041-41xx-psoc-4100s-capsense-pi... . Download the design files and look for the flex PCB layout.

CY8CKIT-041-41XX Design Files.zip

Regards,

Bragadeesh

Regards,
Bragadeesh
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thank u so much!

We have a similar design that implements prox sensor and shield electrode in a flex PCB.

I've looked at this product before, but it doesn't seem to have a shield  electrode.

It has a diagonal of 9cm, but it can only achieve a prox-sensing  distance of 5cm.

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We recommend you to have a proximity sensor with diagonal equal to the proximity distance required.

On this kit, the hatch (shield pattern) can be connected to the shield pin, P3[5] or to ground by a three-pad 0 ohm resistor (R75 and R76). By default, R75 is mounted on the kit, which connects the hatch to the shield pin.

The hatch below is connected to shield only.

pastedImage_0.png

Regards,

Bragadeesh

Regards,
Bragadeesh
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pastedImage_0.png

That is to say, the example projects Cypress's website give doesn't have a driver for this shielding, right?

Can I manually re-drive this shield myself?

pastedImage_1.png

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Shielding is not a separate driver and is implemented by the CapSense component it self. To enable the shield electrode, you need to enable the shield electrode in the CSD settings tab of the Advanced settings in capsense component.

Shield electrode is included as part of the below code example. Could you please clarify your question

https://www.cypress.com/documentation/code-examples/ce214023-capsense-proximity-sensing

pastedImage_1.png

Regards,

Bragadeesh

Regards,
Bragadeesh
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My question is that the diagonal length of this sensor is 9cm, but it can only achieve a prox sensing distance of 5cm.

is that because there is not a ALP filter?

another,the perfomance of the FPCB is far worse than PCB(CY8CKIT-024),which can achieve 12cm-prox-sensing distance.why?

pastedImage_0.png

in above picture, CY8CKIT-024 combines with CY8CKIT-041-41XX,can it achieve a prox distance of 12cm?how to achieve it?

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Cp per sq inch of flex PCB is greater when compared to FR4 PCB. Note that sensitivity of the proximity sensor is inversely proportional to the Cp of the sensor. That is why you would observe less prox distance in a Flex PCB compared to FR4 PCB.

You could even use a wire as prox sensor as suggested earlier to increase sensitivity.

Regards,

Bragadeesh

Regards,
Bragadeesh
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but it cant add a shield electrode while using a wire?

best regards

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Hi,

You can place a flex PCB with shield separately at the bottom of the proximity electrode.

Regards,

Bragadeesh

Regards,
Bragadeesh
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thanks.

i watched this video,but it doesn't work.

I want to use flexible electrodes to achieve a large proximity-distance.

both flexible electrode and long distance are vital.

best regards

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