Haptic Pad Electromagnetics project

Discussion in 'The Projects Forum' started by mikeysela, Dec 25, 2010.

  1. mikeysela

    Thread Starter Member

    Jul 24, 2010
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    1
    Hey guys,
    I am working on a project in which I will energize a series of electromagnets embedded underneath the surface of a mouse pad at the appropriate time depending on information from a PC to an Arduino, which in turn will energize one or more electromagnets at the appropriate time. The energized electromagnet will attract an iron core that will be placed in the centre of an optical mouse.
    Attached below is a simple schematic showing only the circuit for 1 electromagnet (I will have a total of 25 of them placed in a particular orientation on the pad).

    Component Data Sheets:

    MOSFET: http://www.fairchildsemi.com/ds/BS/BS170.pdf
    Diode: http://www.nteinc.com/specs/original/1N4001_07.pdf
    Electromagnet: http://www.cn-hcn.com/en/product_show.asp?id=171

    As you can see, the electromagnet is rated for 3W at 25N/2.5Kg holding force.
    For the PC-to-Arduino stage, I plan on coding some kind of simple GUI on Visual Basic that will transmit real time data to the Ardunio, which I will analyze in the Arduino end and energize the electromagnets accordingly. From there, that energized electromagnet will attract the mouse and the mouse will move to that particular location on the mouse pad.


    Questions for you:
    1. Are my choices of components good for this electromagnet spec? Does this circuit need any alterations? I could not find the current requirement for them, but I am pretty sure I will be using the 12V supply but I can change this.
    2. Is Visual Basic a good choice for the PC end of things to communicate with an Arduino in order to send it real time data? OR maybe I should use Processing since it is specifically designed for arduino?
    3. One of the biggest challenges I can see here is not knowing the mouse’s position on mouse pad at any given time. This means that the proper data can be transmitted on a OnMouseHover command (just an example) in the GUI, which will cause a certain electromagnet to be energized. However, the actual physical mouse position on the pad may be too far from that particular electromagnet and will feel no attractive forces. How can I accommodate for this and somehow map the physical location of the mouse to the virtual location.

    I would appreciate further input if I missed anything guys and appreciate all help. Thanks very much.
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    By having the magnets arranged and activated by rows and columns, and with proper attention to the timing of those row by row and column by column activations.

    The ones which produce a 'movement' in the mouse will be the correct location. Making the resolution dependent on the size and number of electromagnetic grid points.

    You need to keep something like the roller ball in the mouse, for a way to signal the outside world that it has moved. knowing where you are in the magnet sequence and comparing that to when you get a movement response from the mouse tells you your present location, your distance from the target location and which way to sequence the magnets to move you there.


    Another way - like describing where you are on a chess board.
     
  3. wayneh

    Expert

    Sep 9, 2010
    12,100
    3,036
    Before I got very far with this, I'd confirm that the proposed magnet can actually pull a mouse across the anticipated magnet-to-magnet distance. I'm skeptical that you can do that. The field may be strong at the face of the magnet's core, and might be able to pull from a reasonable distance parallel to the field lines (eg. from above the pad down onto the pad), but the field dissipates hugely in the same plane, perpendicular to the field lines.
     
  4. mikeysela

    Thread Starter Member

    Jul 24, 2010
    87
    1
    The reason was that that was the original concept design and the electromagnets have already been paid for. I have about 25 of them top spread over an 8 by 8 mouse pad. Is that not enough for resolution? Also, why am i dosing electromagnets with duty cycles? I was just going to turn them on to cause an attraction and then off to stop the attraction and turn the next one on to continue the attraction to the next magnet.
     
  5. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    64 of them for the 8x8 inch mouse pad would be better

    (for 1" resolution)
     
  6. mikeysela

    Thread Starter Member

    Jul 24, 2010
    87
    1
    Unfortunately, the ones I purchased are not very cheap and I could only afford the 25..can I still get decent results?
     
  7. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    (kermit2 shrugs his shoulders)

    Depends mostly on your perseverance I suppose, and upon your choice of approaches. maybe you could figure out something to fill in the holes. Hall effect sensors perhaps.

    Do you GOOGLE much?
     
  8. wayneh

    Expert

    Sep 9, 2010
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    I believe only experimental data can answer that. Critical question to answer: How far can my magnet be from my mouse, and still reliably pull it in?

    I wonder if you used a magnet in your mouse instead of dead iron, if that wouldn't help. You could reverse polarize the electromagnet currently under the mouse and maybe this would help "throw" the mouse onto the new position.
     
  9. mikeysela

    Thread Starter Member

    Jul 24, 2010
    87
    1
    What are you trying to say here? Yea i google, why?
     
  10. mikeysela

    Thread Starter Member

    Jul 24, 2010
    87
    1
    Again, this is ok, but I would have to know the mouse's position on the mouse pad at all times for me to know exactly with electromagnet to energize, correct? This sounds very difficult to me.

    I can do some more experimenting with putting a magnet inside instead of dead iron i suppose, I just do not have the electromags yet, that is the only challenge.

    Thanks very much.
     
    Last edited: Dec 26, 2010
  11. Wendy

    Moderator

    Mar 24, 2008
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    To look at prior art. You may find answers for questions you haven't asked yet.
     
    Last edited: Dec 26, 2010
  12. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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  13. mikeysela

    Thread Starter Member

    Jul 24, 2010
    87
    1
    I apologize Kermit, i guess i just did not get your humor and i thought u were having a sarcastic go at me. Regardless, I appreciate the link and your advice so I apologize for misinterpreting your response.

    M
     
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