TTP 223 Touch Sensor - extending with wire

Other Hardware Sensors
1

Hi, I'm experimenting with this sensor with the ultimate aim of having reliable touch through 3mm acrylic.

I'm not sure if it's going to be stable enough for purpose yet and I am using trial and error at this stage.

Has anyone tried this? Got any advice as to type of wire, shielding, grounding, relationship between size of touch area and other factors. Anything really!

I've soldered some solid core copper wire to the small hole by the existing touch pad and made a 6cm circle out of it. Putting my hand near it makes the light come on, even through the acrylic.
But it seems a bit unstable - I get very different results depending on what is near the microcontroller, the sensor or the antenna. I've had less luck with larger circles.

Anyone got any secrets?

2

i made macros keyboard with such sensors. hot glued on 4mm glass plate and covered with 2 layer of semitransparent sticky foil.

3

Are you using a bare chip, or a ready-made board; eg,

If it's a ready-made board, it looks like you just get a digital output.

If a bare IC, you will have to find & study the chip's datasheet and any other available resources; eg, application notes, etc...

4

I’m using the board pictured above.

I’ve soldered a wire to the tiny hole by the touch pad and a ring of copper wire to that.

Also tried scraping away the surface of the touchpad and soldering straight to that. I’m not sure if there is any difference.

It’s working fine as far as it goes, but it does behave very differently depending on environmental factors I haven’t quite worked out yet.

How do I create a more stable environment?
Can I use some material as shielding? Between the LEDs and the extended sensor for example. Would earthing anything nearby help? How does the size of the copper ring affect things?

I’m trying to answer these questions using trial and error but some guidance in science or from someone else’s experience would be amazingly helpful!!!

5

Why didn't you just glue the circuit board onder the acrylic.

If you want to use a custom touch area, then cut the via between board touch pad and small solder pad underneath. Use a 4mm dril, and countersink a small hole by hand to break that through connection. Then solder a wire to the small pad underneath. Keep wire between board and custom touch pad short.
If you are on battery power (no earth/ground), things could get unreliable. To fix that you also need a ground plane around your custom touch pad. The ground plane must be connected to the ground pin of the touch board. See this page.
Leo..

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