Touch sensing through metal - Page 1
Forum section: electronics / projects

author: Corporate666
author_rank: Unknown
timestamp: July 26, 2013, 11:25:18 pm
content: Anyone got any experience with this? I seem to remember a company that was making some kind of sensor that detected micro flexing of the metal as you touched the surface... but my google-fu is weak and I can't find it now.I know you can do simple detection of a touch, but this application would require a slider and a couple of buttons.Anyone remember the technology I am thinking of?

author: skipjackrc4
author_rank: Regular Contributor
timestamp: July 27, 2013, 12:15:34 am
content: Metal-over-cap? Microchip has something to do that, I believe.

author: C
author_rank: Super Contributor
timestamp: July 27, 2013, 01:22:21 am
content: no experiencebut these may helpa strain gage comes to mind first.Force sensing resistormicromachining sensorsC

author: fcb
author_rank: Super Contributor
timestamp: July 27, 2013, 11:15:29 am
content: Bang & Olufsen used capacitive sensing through <1mm of metal on BeoCenter 2You need something like aluminium, instead of copper. Google Qprox, projected touch capacitance. And as the OP said - look at Microchip (and MSP430) websites.I wouldn't bother with using strain-gauges unless you need a precise measure of finger pressure.

author: SeanB
author_rank: Super Contributor
timestamp: July 27, 2013, 03:03:36 pm
content: I have one of those to strip, the glass front panels were broken, so it was scrapped.

author: Corporate666
author_rank: Unknown
timestamp: July 27, 2013, 04:23:25 pm
content: I did end up finding some documents from Microchip... I swear there was another company doing that but I think Microchip might have bought them out.http://www.microchip.com/pagehandler/en-us/technology/mtouchbuttons/technology/metal-over-cap.htmlHas anyone used the Microchip method and aware of any of the pitfalls? From searching online, most of the references to Microchip's approach lead back to Microchip app notes and data sheets, so it sort of looks like it isn't very popular on the market.

author: nctnico
author_rank: Super Contributor
timestamp: July 27, 2013, 08:07:23 pm
content: I did a touch sensor design using standard piezo elements. It did take some signal processing to figure out which button is pushed when multiple sensors are mounted on the same front. An ARM controller with sufficient oversampling made the hardware dead simple. I think you should be able to create a slider but it will take some software development effort to figure out what the position is.

author: Jon Chandler
author_rank: Frequent Contributor
timestamp: July 27, 2013, 08:09:56 pm
content: Microchip is the only solution I have seen. I don't recall ever seeing a metallic touch panel in the wild.

author: lgbeno
author_rank: Frequent Contributor
timestamp: July 27, 2013, 08:15:49 pm
content: I believe it was microchip inductive touch like everyone else is saying by it never took off like cap touch.Sent from my iPhone using Tapatalk 2

author: echen1024
author_rank: Super Contributor
timestamp: July 27, 2013, 08:32:11 pm
content: You might as well just overlay a Resistive touch panel over the piece of metal. Otherwise listen to the others. I remember reading about the Microchip application a while back.

author: nctnico
author_rank: Super Contributor
timestamp: July 28, 2013, 04:36:19 pm
content: Cypress also has a lot of capacitive touch chips. According to a supplier of capacitive touch foils the Cypress chips are the best on the market and they have auto-tuning.

author: Corporate666
author_rank: Unknown
timestamp: July 28, 2013, 06:03:52 pm
content: Yeah we have been using Cypress Capsense for a few years now - I know they were providing the solution for Apple, at least they were years ago for the iPhone/iPod. I just had an application for an ultra modern looking consumer device and a clean smooth metal bezel would have looked perfect, and I remembered reading about touch through metal. Looks like it's either piezo or capacitive... the former being expensive, the latter being tricky to get right.I don't want to get a lot of units in the field only to start having issues, so I think we'll just cut a hole in the panel, put a PCB in there and use capsense. Oh well... such is life.