Capacitive Touch Switches

[andys]

i haven't got a finished project to show as I'm still working on various ways of achieving what I'm after, but I've been playing with these little devices TTP223 Mini Red Capacitive Touch Switch Button Self-lock/No-lock Module Arduino | eBay
and wanted to bring them to the attention of anyone who isn't aware of their existence, as I was.
They're dirt cheap but very versatile, being able to set the switch so it's either high or low on power up, and can be set to be latching or non latching with a simple solder bridge on the board. They can't handle much current so you'll need to use a relay, and it needs feeding 5v so you'll need to include a little regulator in the circuit, but they're tiny and cheap too.
So what's the big advantage? Simple, they will work when attached to the back of a switch blank and be completely invisible! They sense your finger touching the surface in front. No more aftermarket switch drilled through, you could use any blank, or in fact any plastic/textile surface in the van as a switch, maybe even print it's purpose and position on the front. You may need some sort of feedback to tell you if it's on or off, eg an led, if it's not going to turn on something obvious like a light, but they're perfect for anyone who wants to keep things stealth and factory looking.
You may be interested you may be not but I've been impressed by how well they work and thought they were worth bringing up.

 

[Fish]

Lovely may have a need for these in Phase 3.

 

[andys]

Don’t suppose anyone else has had a fiddle with these, I’m not having much success? I’ve tried wiring them up as latching with startup state off and they work perfectly on the bench, but as soon as I try and mount them behind something, the pressure of the surface touching them seems to keep them on permanently. I’ve tried mounting them behind a variety of non conducting materials (though the only one that matters is the plastic of the switch blanks) including acrylic, acetate even wood veneer, and they all make the switch stay on. I’ve varied the adhesive and even done a press fit with no adhesive at all and I get the same results.

it’s really frustrating because they’re exactly what I need, the led that illuminates during the ON state is even visible through the switch blank in the dark so wouldn’t even need a separate indicator LED. They’re only pence so I’ve ordered another batch in case mine were faulty but just wondered if anyone with more electronic knowledge than me could shed any light on what’s going on.

 

[Pete C]

I will buy a few and have a play. Is it possible to mount them just off the touch surface ?

Pete

 

[mmi]

Don’t suppose anyone else has had a fiddle with these, I’m not having much success? I’ve tried wiring them up as latching with startup state off and they work perfectly on the bench, but as soon as I try and mount them behind something, the pressure of the surface touching them seems to keep them on permanently. I’ve tried mounting them behind a variety of non conducting materials (though the only one that matters is the plastic of the switch blanks) including acrylic, acetate even wood veneer, and they all make the switch stay on. I’ve varied the adhesive and even done a press fit with no adhesive at all and I get the same results.

it’s really frustrating because they’re exactly what I need, the led that illuminates during the ON state is even visible through the switch blank in the dark so wouldn’t even need a separate indicator LED. They’re only pence so I’ve ordered another batch in case mine were faulty but just wondered if anyone with more electronic knowledge than me could shed any light on what’s going on.

Actually yes. I got inspired by your first post and ordered quite a few. Different supplier though --> AliExpress Anyways, they look the same?
I tried them of course "stand-alone" to verify "the sensitivity", heat build-up, etc. Of course hoping could use them outside of spec at 12V(16V) but as expected it's a definite no-go.

I set up a prototype by hiding the gadget inside a blank switch cover on T6 dash. Put it just behind front plate of the cover. But didn't actually implement any real function yet so no long term experiences - just playing with it to get the feeling how it works: on/off, doubletriggering, mistriggers, etc.

Left the experimenting with impression that it works actually quite well, the installation desensities it a bit so needs a "firm full finger" touch on the surface. So using the other buttons unlikely triggers this one. To operate the switch with gloves on then seems to be a no-go.

However, the material in front of this switch seems to a kind of critical. I'm pretty sure that less is better, and probably no glue on the sensor side. Sensitivitywise can't be thick either.

To make it look nice I'm wondering how to engrave my own symbol on the surface to get "the OEM look" on the switch from LED behind .

EDIT: Clean out of the link.

 

[andys]

Actually yes. I got inspired by your first post and ordered quite a few. Different supplier though --> US $0.65 5% OFF|10PCS/LOT NEW TTP223 Touch button Module Capacitor type Single Channel Self Locking Touch switch sensor-in Integrated Circuits from Electronic Components & Supplies on AliExpress - 11.11_Double 11_Singles' Day Anyways, they look the same?
I tried them of course "stand-alone" to verify "the sensitivity", heat build-up, etc. Of course hoping could use them outside of spec at 12V(16V) but as expected it's a definite no-go.

I set up a prototype by hiding the gadget inside a blank switch cover on T6 dash. Put it just behind front plate of the cover. But didn't actually implement any real function yet so no long term experiences - just playing with it to get the feeling how it works: on/off, doubletriggering, mistriggers, etc.
View attachment 53727
Left the experimenting with impression that it works actually quite well, the installation desensities it a bit so needs a "firm full finger" touch on the surface. So using the other buttons unlikely triggers this one. To operate the switch with gloves on then seems to be a no-go.

However, the material in front of this switch seems to a kind of critical. I'm pretty sure that less is better, and probably no glue on the sensor side. Sensitivitywise can't be thick either.

To make it look nice I'm wondering how to engrave my own symbol on the surface to get "the OEM look" on the switch from LED behind .

Sounds like we’ve been trying the same things. I had thought of getting customised water-slide transfers for the function, they seem to be available thanks to toy restorers. Be a pity if they can’t be made to work, they would be a very neat way of adding non standard switches

 

[andys]

I will buy a few and have a play. Is it possible to mount them just off the touch surface ?

Pete

Please do, the hive mind might crack it

 

[Pete C]

Ok, got some of these and had a play. In the photo below, I have used the lid of a standard plastic food container, and the switch is stuck to this with some foam double sided tape that I had lying around. The tape is about 2mm thick.

It all works fine so far. I'm going to see if I can get hold of some proper switch blanks to test them out a bit more.

Pete

View attachment 54231

 

[andys]

Ok, got some of these and had a play. In the photo below, I have used the lid of a standard plastic food container, and the switch is stuck to this with some foam double sided tape that I had lying around. The tape is about 2mm thick.

It all works fine so far. I'm going to see if I can get hold of some proper switch blanks to test them out a bit more.

Pete

View attachment 54231

View attachment 54232

Hmm thanks, I wonder if my original ones were faulty. By coincidence the 10 new ones I ordered from ebay arrived today so I'll have another go soon

 

[Pete C]

I doubled up the foam tape, and they stopped working - clearly 4mm gap is too big.
Sensitivity does not appear to be voltage dependant.

Pete

 

[Pete C]

A bit more. I stuck 2 of these (same tape) behind a CBE blank, and they work fine.

Pete