Touch screen using range sensors

This touch screen relies on measurements from two range finders to track your finger as you press buttons. [James Alliban] put this together as his first Arduino project. We’re familiar with [James'] background because of his informative augmented reality business card. As the Arduino picks up data from the range finder it sends it to a Flash script that is running on the PC.

As we watched the video after the break a lot of questions came to mind. What kind of angle do these Ping sensors have? Will there be interference problems if they were placed perpendicular with each other? Would you get more accurate data if they were not both on the top of the screen? For now this is just a preliminary experiment, but we like the concept and may give it a try ourselves.

[Thanks Juan]

Comments

  1. biozz says:

    its almost annoyingly accurate for a sonar sensor

  2. Joe says:

    Over 20 years ago, I used a digitizer that was a long metal box with ultrasonic transducers at either end. You placed the box at the head of a table and the table became a large digitizer. It worked very well for CAD.

  3. Nice project, those sensors are very accurate in measurements and easy to use.
    They would have interference with each other but it depends on the timing, if you let the signal from one sensor to die out to make a second measurement, you won’t have any problems.

  4. Marco says:

    For some VR project with cheap ultrasound transceivers we had a best case resolution of 1mm. The real world results were of course a lot worse thanks to delayed echos and diffusion.

  5. George says:

    old news. saw this about a year ago

  6. bob says:

    Do it without the second rangefinder

  7. xSmurf says:

    This could be so much better using USB AVR and emulating an HID pointing device!

  8. biozz says:

    @bob a single range finder only works in one dimension

  9. Gottabethatguy says:

    If you had one sensor on top and the other on the bottom how would you triangulate the position?

  10. Eric says:

    This is very similar to this product, which I bought off Woot for about $40

    http://www.woot.com/blog/viewentry.aspx?id=12461

    The only difference is it makes use of a stylus emitting the ultrasonic frequencies rather than reflecting them off a finger or other object.

    Still for $40 it works surprisingly well.

  11. tech-on-pest says:

    would this work with 4 sensors at the 4 corners of the screen(to give full screen touch)?

  12. toss says:

    Theres an exhibit at the Carnegie Science Center that uses 15 of these to track on 3 dimensions. So a lot more can be done with this. Pretty interesting though.

  13. bob says:

    @biozz @gottabethatguy
    them there rangefinders are 2x (2x ultrasonic transducers). only 2 transducers are needed for 2d positioning, and theres four there. 1 transducer sends pulse, then waits for the reply, other one just waits for the reply. all is good.

  14. pall.e says:

    Hey I don’t know much about micro controllers and am still learning anything about electronics, but is there any reason you need the arduino on here? Is it possible to hook the sensors directly to the computer through a serial interface?

  15. Dizz says:

    It depends on wich sensor modules that are being used. some can speak rs232 (well moste likly seriall at ttl levels) so den you just ned a max232 or similar to connect to the computer. some send a analog signal coresponding to the distance so you nead an ad like well the line in on your soundcard.

    And some are stupid so you need to build your on circuit to amplify the signal and then connect it to an ad. and you also need time the pulses your self. then the asmplingrate of your ad and the precision of your timer decides how accurate you can be. but the speed of sound is known so you could calculate this.

  16. James says:

    @bob – what’s the time you’d have to switch over though. I mean if it’s <12" from object to sensor you'd have about 2 uS to switch the sender channel on the IC into sensor mode, significantly less if the sensor and finger were close together.

  17. Gottabethatguy says:

    @bob, I suppose that would be true had the system been built from scratch but since it was built using prebuilt modules, two are needed.

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