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Thread: Teensy 3.0 / 3.1 - Using the touch inputs

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    Teensy 3.0 / 3.1 - Using the touch inputs

    Hi

    Can anyone advise where I may find some information on using the Teensy 3.0 / 3.1 touch inputs.

    I am interested in making a custom keypad and it would be useful to have some guidance.

    Is it possible to combine the inputs to achieve more than 12 buttons. I was kind of thinking you may be able to use a PCB design similar in appearance to that used in a traditional keypad PCB. That is electrically isolated concentric circles allowing 2 or more pins to be touched simultaneously on one pad.

    Also can the inputs be covered or do you need to actually touch the metal pad?

    Thanks
    Ex
    Last edited by Experimentalist; 02-12-2014 at 03:47 AM.

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    Senior Member+ MichaelMeissner's Avatar
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    Here is an old post where Paul S. explained the touchRead functions: http://forum.pjrc.com/threads/23703-touchRead-and-I2C

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    Much obliged, will read now

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    Just read it and that is all about using a shield with an I2C interface. I want to use the native touch functionality. Do you know where I can find info on the touchread? I couldn't see anything on the Arduino web site

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    Right, I evidently had the wrong article bookmarked. I did a google search and found this: http://njhurst.com/blog/01356576041. This was the discussion that referenced it: http://forum.pjrc.com/threads/35-Tou...ers-rotary-etc

    Sorry about the initial post.

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    Quote Originally Posted by MichaelMeissner View Post
    Sorry about the initial post.
    Very kind of you to take the time in the first place, thanks for the update :0)

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    I don't need touch input for my current project but I'm definitely interested in playing with this. Is there any guide available about how those touch inputs should be designed, hardware-wise? I just see "here's some copper, ah and there as well, we can make sense of that with black magic!", but that's about it.

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    I recall a recent article on this in Circuit Cellar magazine.
    It used an oldish microprocessor without specialized touch input - so some of the firmware in the article is replaced with (better) hardware, on the K20 chips. Seems like most new Cortex M3 and up have touch inputs, so there are app notes to be had. I suppose this is for fancy appliances like washing machines.

    My Bosch kitchen range has a touch control panel. Recently, half of it quit working (left side buttons).
    I removed the back of the range, etc., and found that the PC board had come loose from the front panel mounting. The 1/2 in. sq. pads on the PCB were thus 1/2 inch from the panel. Bosch just used thin double-sided foam to mount the board. I found some hopefully better really sticky tape (3M). My cure was after paying $100 for a tech to come and "fix" it. He just stuck it back on and of course it fell off again a few days later.

    The heat does affect the adhesive.

    This PCB is like 12 in. long, has several high-pin-count chips, fancy vacuum fluorescent display.
    Last edited by stevech; 02-12-2014 at 05:48 PM.

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    Quote Originally Posted by christoph View Post
    I don't need touch input for my current project but I'm definitely interested in playing with this. Is there any guide available about how those touch inputs should be designed, hardware-wise? I just see "here's some copper, ah and there as well, we can make sense of that with black magic!", but that's about it.
    When I played with it, the important thing was to make sure you and the Teensy share grounds. If the Teensy is battery operated, you need to touch a ground wire. Presumably the same would be true if your shoes act as an insulator.

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    Assuming the principles apply as well to my kitchen range's controls, seems to matter not what shoes we do/do not have, and the floor is wooden.
    Not true in the case of my range, but I've seen some that have two adjacent pads and the finger capacitance couples between the two, rather than only to ground.

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    I just discovered an appnote by freescale that describes the design process. As I understand it, it might be possible to create sliders and such with a piece of cardboard and sticky copper foil!? That's cool, maybe we could even create a touch ball or some other 3D touch input device.

    Unfortunately, the most prominent feature of that appnote is the ugly typography and that lowers my TL;DR threshold significantly.

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    Quote Originally Posted by christoph View Post
    As I understand it, it might be possible to create sliders and such with a piece of cardboard and sticky copper foil!?
    See earlier post above, courtesy of Michael Meissner, where someone has done nearly that, same principal. Here is the link again:

    Quote Originally Posted by MichaelMeissner View Post
    I did a google search and found this: http://njhurst.com/blog/01356576041

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    Ah now I see it! When I first read the blog entry I didn't realize the simplicity of the slider. OTOH, it gives funny readings and seems to require a common human/device ground, but it's certainly a good start.

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    Quote Originally Posted by christoph View Post
    New link ..............

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