TTP223 big touch area/item leads to unexpected behavior

[terraduino]

Hi,

I've some TTP223 soldered to PCBs which work pretty nice. I power these with 2 AA (~2.7V) or 3 AAA (~4V) battery packs. With a very small touch area of about 1 cm² the sensors activates in approx. 1mm distance. That's fine for some projects but now I want to trigger it through 1-2 cm thick wooden board.

To extent the distance, I soldered a wire to the PCB's copper area and tried different materials, e.g.    30x30cm aluminum foil, 10m copper wire curled up, 20x15cm metal grid.

Funny thing: when I attach one of these larger items, I cannot trigger the IC with getting near it or even touching it. Instead it gets triggered when I touch the battery pack.

Maybe anyone has an idea why this happens and how I can avoid this?

Thanks and best

[terraduino]

I still could not find a solution for this.
Are there other IC with similar logic like the TTP223 I could test?

Thanks & best

[tinman13kup]

There are many touch and proximity ic's out there. The question is whether you can deal with the smd chip and making the board for it.

I have some proximity chips in a sot23-6 package, which are not horrible to deal with, but are pretty small. These chips use resistors to change the sensitivity taking into account distance and size of the pad. I had a breadboard setup using 1/4" acrylic sheet with a 1/2" brass pad. I had the distance down to 1/4" from the surface, which allowed me to have a second sensor an inch away.

There are many other chips that can do much, much more , such as touch slide switches and such. Go to Digikey.com and look at them. Just make sure and do your homework to see if you can actually deal with the inputs/outputs/programming. Not everything is arduino compatable

[Wawa]

Try a metal sheet/plate/foil with holes that are 5-10mm bigger than the touch fields.
e.g. circular touch fields inside the holes are 25mm, and the holes are 32mm.
Glue the foil to the wood.

Connect the big sheet (with as many holes you want) to touch sensor ground, with short wiring.
Connect the circular touch fileds (e.g. 25mm washers) to the sensor inputs.

Keep sensor wiring short and away from that ground plane (reduces sensitivity).
Note that those chips calibrate on bootup, so disconnect/reconnect power if you make changes.

5mm wood should be possible, 10mm maybe.
10mm glass is not a problem (did that).
Leo..

[terraduino]

@tinman13kup
Thanks for the suggestion. I had some difficulties to find the best search term but I found MTCH112:
http://ww1.microchip.com/downloads/en/DeviceDoc/41668A.pdf

Looks like this is an option I could try.


@Wawa
Interesting suggestion, thank you.
Will take a while but I'll give it a try.

Best

[tinman13kup]

Just found my stash of proximity detectors. Mine happens to be the MTCH101T. I have a couple other more involved chips I have yet to try out, just waiting for the right project and motivation.

[terraduino]

@tinman13kup
Interesting IC, thanks.