0
\$\begingroup\$

First off, I know nothing about electrical engineering. So please bare with me.

I'm designing a faceplate for a moto360 smart watch that has a small area that overlays the bottom edge of the screen. Set into that area is 3 buttons made from a clear orange resin that act as a stylus.

These buttons correspond to tabs programmed into the on screen watch face. Pressing these buttons should trigger the software to switch to the corresponding tab and cause a patch of the screen that is hidden by the plate to turn bright white just below the contact point. This illuminates the clear resin button, giving the illusion of a tiny LED.

As you may have guessed, I didn't realize that simply adding a drop of rubber from an old stylus to the bottom of the button wouldn't be enough to trigger it.

I've done some reading and I feel confident enough to know why. Basically, not enough of a draw to pull any electrons from the screen? (Not really the point of this post either way.)

Anyways, my question is, is there a type of affordable space age material that I could attach to the bottom of the 2mm diameter button that would work? Or maybe some kind of clear conductive resin or additive that my caster could use?

Here is a picture of the tiny tiny button assembly as currently planned. The orange pieces are the clear resin and slide into the green pla section. The black dots represent the now useless stylus material.

http://puu.sh/iwnnB/b586ae5189.jpg

This is a very rough picture of how the final plate should look when assembled. This is not an item I have made, but it is a decent representation of how the item should sit around the watch.

https://goo.gl/photos/E2dc9jmBQumnRcdcA

\$\endgroup\$
1
\$\begingroup\$

It depends on the kind of touchscreen it is. At this point, I think most technology is based on capacitance, and not multi-layer resistance. If this is the case, you might want to look into how those touch-screen capable gloves work. These are gloves that have a finger and a thumb covered in some material that works with modern touchscreens.

There is also apocryphal evidence that a hotdog, cold out of the fridge, works on these screens. Make of that what you will.

\$\endgroup\$
0
\$\begingroup\$

At a guess, what you want to do is simply not possible. As a check, try this: make a stylus out of metal (preferably not aluminum - copper would be better) which ends in a point which is about the same area as the area of your buttons where they contact the face plate. See if using that stylus activates the touch area on some existing app. I suspect it won't, and I can't explain why without getting into questions of capacitive coupling which you won't understand.

If a conductive material producing a small contact area doesn't work, there is no way you can get your buttons to work.

\$\endgroup\$
  • \$\begingroup\$ Maybe a conductive resin is the way to go then? Now I just gotta figure where to go for info on that. lol I kinda just stumbled upon this one. \$\endgroup\$ – GoGoCharlie Jun 21 '15 at 9:40
  • \$\begingroup\$ No, what I mean is you need to try it. If it doesn't work, going to conductive resin is not going to help. And I strongly suspect it won't work, although I could be wrong. \$\endgroup\$ – WhatRoughBeast Jun 21 '15 at 18:57
  • \$\begingroup\$ It's definitely possible in general to have things that activate a capacitive touch screen. There have been several products (game controller/joystick styled) that attach to the surface of the screen. I don't know how they work, and it may not be able to be as small or transparent as OP wants, but the general idea is definitely possible. (I think there may be a conductive path to the user's hand involved.) \$\endgroup\$ – Kevin Reid Sep 29 '15 at 14:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.