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Help with robot using capacitive touch — Parallax Forums

Help with robot using capacitive touch

xanaduxanadu Posts: 3,347
edited 2014-01-10 13:32 in Robotics
I have this really cool project, completely finished, sitting on a desk for a month now, and I really want to post it here but...

All I need to do is figure out how to "touch" an iPhone screen (capacitive) with ________ and a servo. So mechanically everything is there except the material to make the screen think a human is touching it.

From what I know about capacitive touch screens, your bodies resistance is transferred though the stylus. In this case nobody will be holding anything, it's just a servo moving, tapping a soft button on the screen. Unfortunately the button cannot be mapped to a regular good ol tactile button.

Would there be some way to fake this resistance issue?

Comments

  • xanaduxanadu Posts: 3,347
    edited 2014-01-09 13:04
    Okay I think I found some better search terms, I searched for servo and capacitive touch and found this - http://electronics.stackexchange.com/questions/60070/how-do-i-make-a-micro-controller-act-as-a-finger-on-a-touch-screen

    I will try that, looks like I can even ditch the servo if that works. Neato.
  • xanaduxanadu Posts: 3,347
    edited 2014-01-09 13:19
    Wow, nice I guess I asked a minute too soon.

    If you want to emulate a finger press you can put a piece of foil (or anything conductive) and short it to the USB ports ground. Works like a charm. Less moving parts. I will probably use a transistor to control the foil.

    Now I can say I foiled my phone :)
  • jdoleckijdolecki Posts: 726
    edited 2014-01-09 15:20
    Don't they already have gloves that will work on a screen while your finger stays warm?
  • xanaduxanadu Posts: 3,347
    edited 2014-01-09 15:54
    jdolecki wrote: »
    Don't they already have gloves that will work on a screen while your finger stays warm?

    Yes, those gloves probably rely on your hand being in them to work though.
  • xanaduxanadu Posts: 3,347
    edited 2014-01-09 16:03
    Also, if you need to do this, you cannot run a wire from the screen to anything unless it is a very short ~3" run. Just the length of a wire will set off the sensor, even if you aren't touching the wire. I discovered this by clipping a 12" clip lead to the foil attached to the screen, it essentially just holds down the button.

    So what I did was this:

    attachment.php?attachmentid=106052&d=1389311997

    2N2222, the source would be the same ground as the phone is using. To "press" the button I'm using Parallax Touch sensor, I can't find a link to this one, but it's like this - http://parallax.com/product/30056 with shorter leads. I'm only using it because it looks a lot better than tin foil and I also have a bunch of them laying around. Energize the gate and voila, button press.
    IMG_0112.JPG
    800 x 450 - 65K
  • ercoerco Posts: 20,255
    edited 2014-01-09 16:07
    You're going to build an iPhone into a project just to bypass the capacitive screen? Seems kinda pricey. :)

    I added capacitive sensing to my bot for exactly three cents: http://www.youtube.com/watch?v=3e92B8JNNns
  • xanaduxanadu Posts: 3,347
    edited 2014-01-09 17:17
    I saw that video the day you posted it, wicked.

    I'm making Panographic Time Lapse (panolapse) rig. You can use any camera, but i have an iPhone 4 laying around doing nothing - and it does pano with ease. The BS2 will handle the rest.

    I didn't know Panolapse was so popular until about halfway through the project. I kinda thought I was pioneering something at first. Anyway it's a nice break to work with the BS2 and not have to worry about regular robot factors.

    I will post it in the projects pretty soon :) I'm debating on waiting until I have an actual panolapse to show.

    I'm using the BS2 because there will also be a video for people who don't know what a microcontroller can do for them.
  • xanaduxanadu Posts: 3,347
    edited 2014-01-09 17:20
    erco wrote: »
    You're going to build an iPhone into a project just to bypass the capacitive screen? Seems kinda pricey. :)

    I added capacitive sensing to my bot for exactly three cents: http://www.youtube.com/watch?v=3e92B8JNNns

    At first I just saw "three cents" and a link and assumed I was getting a touch screen on eBay haha.
  • kwinnkwinn Posts: 8,697
    edited 2014-01-09 20:05
    erco wrote: »
    You're going to build an iPhone into a project just to bypass the capacitive screen? Seems kinda pricey. :)

    I added capacitive sensing to my bot for exactly three cents: http://www.youtube.com/watch?v=3e92B8JNNns

    Great idea. It would cost me $0.15 since we no longer have pennies in circulation.
  • ercoerco Posts: 20,255
    edited 2014-01-10 08:31
    kwinn wrote: »
    we no longer have pennies in circulation.

    I did not know that: http://news.yahoo.com/canada-phase-penny-begins-195833349.html;_ylt=A0SO81VfH9BSOQ0AdYxXNyoA;_ylu=X3oDMTEzYzA0MzVpBHNlYwNzcgRwb3MDMQRjb2xvA2dxMQR2dGlkA1ZJUDI4Ml8x

    In similar fashion (per that article), I did not know the "American zinc lobby" could exert so much force on our government and economy!

    Where's the American plywood lobby when I plead my case for robot chasses?
  • kwinnkwinn Posts: 8,697
    edited 2014-01-10 13:32
    erco wrote: »
    I did not know that: http://news.yahoo.com/canada-phase-penny-begins-195833349.html;_ylt=A0SO81VfH9BSOQ0AdYxXNyoA;_ylu=X3oDMTEzYzA0MzVpBHNlYwNzcgRwb3MDMQRjb2xvA2dxMQR2dGlkA1ZJUDI4Ml8x

    In similar fashion (per that article), I did not know the "American zinc lobby" could exert so much force on our government and economy!

    Where's the American plywood lobby when I plead my case for robot chasses?

    It's the good old "to heck with you as long as I'm OK" principle at work. The "American zinc lobby" couldn't care less about the economy in general as long as they are doing well.
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