Making capacative touch buttons - Page 1
Forum section: electronics / general

author: king.oslo
author_rank: Frequent Contributor
timestamp: May 15, 2012, 09:20:54 am
content: I found this an interesting way to save $$$ on push buttons on my next project. An idea: could be integrated into a pcb front panel. I thought it was handy.Check it out:http://tuomasnylund.fi/drupal6/content/capacitive-touch-sensing-avr-and-single-adc-pin

author: Rerouter
author_rank: Super Contributor
timestamp: May 15, 2012, 09:48:16 am
content: with the golden question being how sensitive this approach is, say to pick up a finger through a plastic front panel, and how some desing methods like fitting a led pwm or flat out, in the middle would effect it, i assume all of it could be optimised around, but my curiousity always holds these type questions incase,

author: steve_w
author_rank: Regular Contributor
timestamp: May 15, 2012, 10:09:11 am
content: Nice work on that; It would be interesting to see how reliable it is.The major micro makers have put a lot into custom capacitive switch solutions so i don't think its that simple. However the video was quite well done and looked good. Are the micro makers inventing expensive solutions to sell more product?I don't know.regardsSteve W

author: Psi
author_rank: Super Contributor
timestamp: May 15, 2012, 11:40:54 am
content: The ATMega32 used there doesn't seem to have the "QTouch library support" line in the datasheet.Some AVRs have it supported on the micro. Though i think it's more a library thing than a hardware thing.I have the qualcomm touch dev kit around here somewhere. It works fine with around 4mm of plastic in between (comes with that).

author: free_electron
author_rank: Super Contributor
timestamp: May 15, 2012, 01:19:24 pm
content: Most microcomtroller makers have released software libraries that you can simply load on any of their cpu's and do this. As for the electrode design : altium has a built in tool that works with the atmel linraries. Simple tell it that if you want a slider,spinner,key or matrix and it generates the electrode shapes for you in the size you want.

author: T4P
author_rank: Super Contributor
timestamp: May 15, 2012, 03:37:34 pm
content: ST has demonstrated a capacitive library for the STM32 Cortex series before, it's in the STM32 libraries you can download for the STM32F4 ( not the disco, just the chip alone )

author: Bored@Work
author_rank: Super Contributor
timestamp: May 15, 2012, 07:29:04 pm
content: Another way to save on pushbuttons and still get a professional looking front panelhttp://www.ebay.com/itm/165x86x0-8mm-20-Key-Matrix-Membrane-Switch-Keypad-Keyboard-DC-12V-/280878730423

author: free_electron
author_rank: Super Contributor
timestamp: May 15, 2012, 10:39:50 pm
content: if you are after reall COOL switches : 1 address: MEC , Ballerup , Denmark ...www.mec.dk. Now those are COOL especially their navigation buttons !another thing i frequently do : get a sturdy foil printed ,make holes in the aluminum backplate and simply poke the guys below through the holes:then overlay them with the foil.Code:FOIL ============================================ALU //// PP //// PP //// PP //// PP ////SW SW SW SWPCB --------------------------------------------------PP is the 'cap'.SW is the switch body.You simply use standoffs to mount the PCB so that the top of the switch capts is level with the aluminum plate. The foil covers everything. You'll have a nice 'click' sound and tactile feedback. and the foil makes everything waterproof. you can get really sturdy foils that can be printed with a laserprinter. ( backside printing ) . then apply spray-on-glue to aluminum and apply foil. done. the foil is transparent by itself so you can even do things like LCD windows.