Is it reliable to put a single button sensor under the LCD or OLED display?

Hallo Victoria,

thanks for the good question.

The performance depends on the display construction, means if there is a metal or GND layer in between.

Idon't have any test with the electrodes behind OLED/LCD.

In passive case, I think should not be a problem, but if the display is activated this could cause a problem.

In case you have the display already, could you please make a short test (using e.g. the TI EVM) with a copper foil placed under the display and test the performance using the CapTIvate Design Center.

I will check also internally for additional information and will let you know.

What do you mean by (if the display controller would be far enough from the sensor), how far is that?

Are you going to use the MSP430 controller for CapTIvate and the control of the display?

Thanks

Regards

Kostas

Hello,

thank you for your prompt reply!

Kostas Aslanidis said:

In case you have the display already, could you please make a short test (using e.g. the TI EVM) with a copper foil placed under the display and test the performance using the CapTIvate Design Center.

I would, but I'm analysing so far, so I have no display to test yet.

Kostas Aslanidis said:

I will check also internally for additional information and will let you know.

Thank you!

Kostas Aslanidis said:

What do you mean by (if the display controller would be far enough from the sensor), how far is that? Are you going to use the MSP430 controller for CapTIvate and the control of the display?

Up to 5 centimeters, but it won't be MSP430 controller. I'm going to use separate MCU. MSP430 controller I'm going to use only for touch input interface only.

Actually, now I realized that the display driver on the display module (not the controller) can interfere with the sensor (I guess most of the available display modules will have its driver PCB tied to the display glass layer).

I will try to get some display samples to test in few weeks, but maybe the ITO way will be more reliable in the end.

Regards

Victoria

Hi Victoria,

ITO would be one possible solution.

Another solution could be, in case you are going to use a pcb to mount the display, to add the sensor on the pcb around the display. In this case you can make use of the proximity detection function when a finger or hand is cumming very close to the display (RED line). 

This solution would also help to be independent of the different display models.

Can you tell more about the application?

Best regards

Kostas

Hello,

Kostas Aslanidis said:

Another solution could be, in case you are going to use a pcb to mount the display, to add the sensor on the pcb around the display. In this case you can make use of the proximity detection function when a finger or hand is cumming very close to the display (RED line).

I cannot see the image (it seems to be broken somehow). However, I'm not looking for proximity detection rather than touch detection (see below my application).

Kostas Aslanidis said:

Can you tell more about the application?

I would like to make "button bar" that can show different icons. So essentially a few displays (placed on a PCB with some small spacing in between) in a size of a finger each with its own touch detection.

Best regards

Victoria

Hello Kostas,

that looks promising. I will test both ways, PCB sensor by your suggestion and ITO and post here results with specific display model.

Thank you very much for your support!