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Cap Touch Sensor IC suggestions? — Parallax Forums

Cap Touch Sensor IC suggestions?

T ChapT Chap Posts: 4,081
edited 2022-05-27 15:51 in General Discussion

Hello all. Years ago I used QT60160, QT1040, QT1081, etc and other variants. At some point I switched over to all LCD touch screens using New Haven 4.3 ($80 each) but they have obsoleted all the versions I use and wont have replacements till the end of the year. I need to come up with a touch screen really fast and the familiar QT parts are all obsolete or zero stock. I searched Digikey and found this part today that has lots of stock:

https://www.digikey.com/en/products/detail/lumissil-microsystems/IS31SE5111A-ZNLS3-TR/14308368

https://www.lumissil.com/assets/pdf/core/IS31SE5111_DS.pdf

On the surface it looks like a good alternative, 15 inputs, you can set many parameters included gain, threshold, it has a built in MCU that I dont need, I'll drive it with P1 via I2C.

Wondering if anyone has used this and has an opinion. It requires making a PCB, ordering stainless stencil etc and machine setup to test it so its a job. Any thoughts or alternates welcome!

The images show an old stripped down keypad I am going to redo. You can see I am backlighting each number on the keypad with a rear mount gullwing LED. This old layout required two parts to the pad.

Comments

  • What about a Nextron screen

  • T ChapT Chap Posts: 4,081

    I'm needing small keypads, 3"x3" or 3"x5" sizes.

    Thanks

  • The Propeller can drive touchpads by itself, without needing an external chip. The Quickstart board has touchpads. There's software for them here:

    https://www.parallax.com/package/propeller-quickstart-touch-buttons-led-spin-demo-code/

    -Phil

  • ercoerco Posts: 20,158

    These modules are cheap and work well, but they are small and work best with tiny fingers. https://www.ebay.com/itm/233946609184

  • I did some code for that touch in Bs2

  • TTP229

  • T ChapT Chap Posts: 4,081

    @"Phil Pilgrim (PhiPi)" said:
    The Propeller can drive touchpads by itself, without needing an external chip. The Quickstart board has touchpads. There's software for them here:

    https://www.parallax.com/package/propeller-quickstart-touch-buttons-led-spin-demo-code/

    -Phil

    Nice! I can test that easily today. Thanks. Will see how it goes.

  • T ChapT Chap Posts: 4,081

    @erco said:
    These modules are cheap and work well, but they are small and work best with tiny fingers. https://www.ebay.com/itm/233946609184

    Thanks for the link, but I have to make my own. Each key is backlit with a graphic overlay. Each button has to have a hole in in for light. There is no way to buy an off the shelf PCB for this. Will be testing the P1 touch idea since it is on the board already.

  • T ChapT Chap Posts: 4,081
    edited 2022-05-29 14:08

    I make a vinyl graphic and attach a 10mil polycarb velvet texture overlay(adhesive backed) on top. The graphic has lots of custom features specific to the application. It requires a custom PCB with backlights to turn on underneath as needed. The 10mil polycarb + vinyl works great on the older QT parts, even 1/8" glass worked great with double sided tape attaching the glass to a PCB. Sensitivity was easy to adjust on QT1081 with the caps. On the 60160 you could set gain, threshold, etc per pad so that problematic pads could be adjusted to work well.

    The TTP229 looks nice, similar to the one I mentioned earlier. There seems to be little or no stock easily found of the part.

  • ercoerco Posts: 20,158

    I had almost forgotten that I made this video about the 8-button version, which has on-board LEDs for each touch pad. And triggering from the backside is a nice option.

  • T ChapT Chap Posts: 4,081

    This is the final layout for the PCBs getting built. I used the Lumissil (old) part SE5111 for now, but added pads for their newest SE5117 that will be available soon that is much more advanced. The pad board will have a 1/8" spacer board to create separation. The USB, Touch and LED boards stack up on top of the main board. Their is a polycarb overlay that covers the pad board and the numbers and graphics are backlit from the LED's through 1/4" holes.

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