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need a touch switch — Parallax Forums

need a touch switch

dmehlingdmehling Posts: 25
edited 2007-09-09 21:11 in General Discussion
I have a disability that makes it difficult to activate different devices (as in pushing buttons, flipping switches), and am planning on using a microcontroller (basic stamp) to help activate these devices. That means they need to be touch activated. I am considering a few different options: the flexiforce pressure sensor, the QT113-D Touch Sensor, or the peizo vibra film tab. Which of these options would be the best?

Comments

  • D FaustD Faust Posts: 608
    edited 2007-09-01 00:16
    look at this: http://forums.parallax.com/showthread.php?p=589699 (LED touch sensor)

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  • UnsoundcodeUnsoundcode Posts: 1,532
    edited 2007-09-01 00:24
    Hi dmehling, I am sure the QT113 would work for you. Using the Stamp you can also configure things like debounce to allow for any unsteadiness in your hand/arm movement, or/and if needed a one touch to select with second touch to confirm switch to prevent accidental switching of devices.

    Testing several different kinds of touch sensors wouldn't be a bad idea, it would certainly be a great learning excersise

    regards

    Jeff T.
  • dmehlingdmehling Posts: 25
    edited 2007-09-02 17:52
    Thanks for the reply. I was pretty much thinking that that touch sensor would be the best option. Now at this point I need to I need to figure out how this thing should connect to my microcontroller. I read through the PDF files that I was able to download in regard to this sensor, but it was very vague about the actual wiring on a breadboard. I am still pretty new to robotics so I need some pretty basic explanation.
  • UnsoundcodeUnsoundcode Posts: 1,532
    edited 2007-09-03 00:34
    Hi, the following link has the datasheet , documentation and source code. The voltage and current requirements of this thing are low so you would be able to run it from the Stamp regulator's +5v and 0v supply. The documentation has very clear and simple schematics and discusses sensitivity adjustment. It only requires a few additional common components and looks like an ideal project for a beginner. If you ever run into difficulty this forum has an abundence of resources.

    http://www.parallax.com/detail.asp?product_id=604-00038

    regards
    Jeff T.
  • dmehlingdmehling Posts: 25
    edited 2007-09-03 17:57
    I found the hookup diagram for the basic stamp, and I think I can figure this out. Do you think I could use this sensor with the basic stamp 1 project board, or do I need a different development board?
  • UnsoundcodeUnsoundcode Posts: 1,532
    edited 2007-09-03 22:21
    If you have the Basic Stamp 1 project board that would be ideal for prototyping your project. You would have to think carefully when the time came to to use the output(s). Each pin can source 20mA and sink 25mA the total across all I/O pins not to exceed source 40mA and sink 50mA using the on board regulator. So normally you would use a component like a transistor, opto isolator or solid state relay to switch devices of higher voltage / current.

    In the mean time connect your touch sensor and write a program to do what you want and test the outputs with a LED. When you get past that stage you can start to design the·switching elements of your project.

    Jeff T.
  • dmehlingdmehling Posts: 25
    edited 2007-09-04 17:39
    On second thought I don't think that development board will work for my purposes. I am wanting the microcontroller to rotate a small servo every time it senses input from the touch sensor. The servo I will be using needs at least 100 mA. I want the development board to supply all of the current I need for this project so I don't have to mess with additional components like relays. Do you know if the super carrier development board can supply that much current? It says that it has a 6-30 V regulator but I don't know what that tells me about the current.

    Also, do I need to make all of the connections for the touch sensor shown in the schematic, or are some of them optional?

    Thanks for your continued advice with this project. You have no idea how much you have helped me.
  • D FaustD Faust Posts: 608
    edited 2007-09-04 18:34
    I think that they are·500·mA regulators.· You could search for the part number.(Found in schematic)

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  • UnsoundcodeUnsoundcode Posts: 1,532
    edited 2007-09-04 18:53
    Hi, the BS1 development board has connections for a servo I believe. So you can drive a servo without a relay.

    The power·for the servo is not taken from the Stamp regulator but from the supply to the regulator.

    The Stamp is used to control the servo and can deal with it without problem.

    Your supply to the servo needs to be 6-7 volts dc maximum·and be capable of supplying the current you require

    The control for the servo is a pulsed 0-5 volts controlled from the BS1 module

    Jeff T.
  • D FaustD Faust Posts: 608
    edited 2007-09-04 21:09
    You'll probably want a boe-bot battery pack.

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  • dmehlingdmehling Posts: 25
    edited 2007-09-09 20:33
    After looking at the data sheet once again, I noticed that it said the sensor needs about 600 mA of supply current. In looking at all of the development boards I could use for the basic stamp, none of them can provide that high of a current. Is this a correct assessment, or am I misunderstanding something? If that is true, then how will I be able to supply the necessary amount of current?
  • D FaustD Faust Posts: 608
    edited 2007-09-09 20:45
    You could add some extra regulators in parallel to boost the output. Basically, two more regulators
    with the ground pins connected, input pins connected, and output pins connected.· Or you could try to find a different regulator with a higher current rating.

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  • UnsoundcodeUnsoundcode Posts: 1,532
    edited 2007-09-09 20:47
    Hi dmehling, you may have misread the data sheet, the data sheet says 600 microamps or 0.6 milliamp. Your original suggestion of using the BS1 project board will do everything you need for this project.

    Jeff T.
  • dmehlingdmehling Posts: 25
    edited 2007-09-09 21:11
    Thanks for pointing that out. When it said 600 µa, I was thinking 600 mA. Having taken Greek, I should have noticed that.
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