1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Looking for a sheet that resists

Discussion in 'Mathematics and Physics' started by jasonbe, Oct 30, 2008.

  1. jasonbe

    jasonbe New Member

    Joined:
    Sep 18, 2008
    Messages:
    346
    Likes:
    1
    Are there thin sheets of material on the market that have resistance levels - comparable to resistors, which vary in a well defined relation to units of distance?
     
  2. Willbe

    Willbe New Member

    Joined:
    Aug 16, 2008
    Messages:
    1,236
    Likes:
    7
    Location:
    MD
    "telo deltos" paper?

    Carbon paper?

    The resistance is spec'ed in ohms per square, believe it or not.
     
  3. Mikebits

    Mikebits Well-Known Member

    Joined:
    May 24, 2008
    Messages:
    6,214
    Likes:
    174
    Location:
    San Diego, Ca
    ONLINE
    Well hell, that makes sence. Never thunked of that :)
     
    Last edited: Oct 30, 2008
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. Hero999

    Hero999 Banned

    Joined:
    Apr 6, 2006
    Messages:
    14,902
    Likes:
    79
    Location:
    England

    Black anti-static polythene bags.
     
  6. jasonbe

    jasonbe New Member

    Joined:
    Sep 18, 2008
    Messages:
    346
    Likes:
    1
    Could you help me find some "telo deltos" paper? I tried to find an internet translation - and did an internet search, and couldn’t find any. I’ve used carbon paper before and never thought of its electrical properties. However, the carbon paper would be exposed to rubbing and I’m afraid that this might change the carbon paper's electrical properties. The black anti-static polythene bags might work, but something more rigid would be better. Something transparent would be the best.
     
    Last edited: Oct 31, 2008
  7. Willbe

    Willbe New Member

    Joined:
    Aug 16, 2008
    Messages:
    1,236
    Likes:
    7
    Location:
    MD
    Back in the 70s we needed to find the characteristic impedance of various shaped conductors. With this paper you paint the conductor shape on the paper with conductive ink and measure it with an ohmmeter. Using a scale factor gives you the impedance.
    BDM (Braddock, Dunn & McDonald) corp. knew where to get this paper, and the correct spelling. With computers this kind of thing is probably obsolete unless it has other uses.
    I hope this helps.
     
  8. jasonbe

    jasonbe New Member

    Joined:
    Sep 18, 2008
    Messages:
    346
    Likes:
    1
    It does. I’m going to check with BDM, if they are still in business. It might also be helpful if you could check the spelling or give me any other names that the paper might go by.
     
  9. jasonbe

    jasonbe New Member

    Joined:
    Sep 18, 2008
    Messages:
    346
    Likes:
    1
    Can anyone help me out with some engineering terms that might help me search the internet for rigid sheets – preferably transparent, or paint that has a well defined rate of resistance per unit distance?
     
  10. Willbe

    Willbe New Member

    Joined:
    Aug 16, 2008
    Messages:
    1,236
    Likes:
    7
    Location:
    MD
    ohms per square
    sheet resistivity
    sheet conductivity
    carbon
    conductive coating
    resistive coating
    flexible
    silvery
     
  11. crashsite

    crashsite Banned

    Joined:
    Nov 20, 2007
    Messages:
    725
    Likes:
    3
    Graphite Rub

    A "poor man's" solution is to grind up some graphite (or buy some graphite powder) and rub it into the surface of some paper. Depending on your application (precision positioning or just needing some varying resistance), it may or may not give consistent enough results.

    At one time, I had experimented with this but, the results weren't great. I didn't really try to refine the technique.
     
  12. MrAl

    MrAl Well-Known Member Most Helpful Member

    Joined:
    Sep 7, 2008
    Messages:
    11,032
    Likes:
    952
    Location:
    NJ
    Hi there,


    Just to note, i tried some "Wire Glue" a while back and although it was pretty neat
    stuff it did not have a well defined resistance as i think you are looking for.
    It was resistive alright, but it varied quite a bit with temperature and bending
    of the base insulator and stuff like that.

    Perhaps you can tell us what you are trying to do or build or whatever so that
    we might know of something else that would work...
     
  13. dknguyen

    dknguyen Well-Known Member

    Joined:
    May 6, 2006
    Messages:
    6,668
    Likes:
    64
    Still hung up on that game board idea are we?
    http://www.electro-tech-online.com/threads/structure-of-resistor-question.86145/
    http://www.electro-tech-online.com/...s-that-gives-them-resistive-properties.86422/

    Are you just going to keep asking the same question over and over until someone tells you what you want to hear? Normally, when people run into problems like this in a project it's one of two things:

    -It's impossible with current technology
    -They are going about it the wrong way

    There was oodles of respones with very in-depth discussion about why your implementation would not work the last few times you asked this question, as well as many alternatives.

    To summarize what he is asking for people who aren't up to speed: He wants a resistive playing board with multiple conductive/resistive playing pieces. Placing the playing pieces on the board is supposed to change the resistance in that particular area of the board, and thus change the resistance seen by 3 contacts connected to the edges of the board. By measuring the change in resistance (or current flow) between these 3 contacts, he wants to monitor the position of all playing pieces on the board. Furthermore, he wants it to be transparent so he can overlay a "graphical map" of sorts onto the board.
     
    Last edited: May 24, 2009
  14. jasonbe

    jasonbe New Member

    Joined:
    Sep 18, 2008
    Messages:
    346
    Likes:
    1
    I might not try to delete the post until someone comes up with an idea or has specialized knowledge relating to the question that makes completion of this project a priority, and then even then I probably won't delete the post. I found the last two responses interesting. I think that the way that this site is indexed, some posts could belong in more than one forum.
     
    Last edited: May 27, 2009
  15. jasonbe

    jasonbe New Member

    Joined:
    Sep 18, 2008
    Messages:
    346
    Likes:
    1
    Did you learn about graphite from a list?
     
  16. jasonbe

    jasonbe New Member

    Joined:
    Sep 18, 2008
    Messages:
    346
    Likes:
    1
    I'm looking for a thin sheet of material that has a resistance level that varies as a function of distance up to a foot or so comparable to the resistance offered by a variable resistor.
     
  17. blueroomelectronics

    blueroomelectronics Well-Known Member

    Joined:
    Jan 21, 2007
    Messages:
    12,536
    Likes:
    168
    Location:
    Toronto, Canada
    Yes but you want it in two dimensions. X-Y
     
  18. jasonbe

    jasonbe New Member

    Joined:
    Sep 18, 2008
    Messages:
    346
    Likes:
    1
    Are you suggesting that some sheets might have a thickness or other characteristic that will make it so that for some reason or another resistance in two dimensions might not consistently vary as a function of distance? I can't say that such sheets are not popular because I am not familiar with the market. However, I am also aware of no natural phenomenon that excludes material from having a certain resistance levels - including the ones that I'm interested in. Hopefully, someone will be able to direct me to something premade - or some things that are readily available and easily assembled.
     
  19. dknguyen

    dknguyen Well-Known Member

    Joined:
    May 6, 2006
    Messages:
    6,668
    Likes:
    64
    You're still ignoring the fact that you can't keep track of more than one piece. Keeping track of one piece is already hard enough due to the minimal changes in resistance (and may not be implementable if you can't find a sheet of material with the tolerances you need).

    But keeping track of multiple pieces is impossibile, even theoretically. Each set of resistances measured does not correspond to a unique set of positions on the board. It only works with one piece per board.
     
    Last edited: May 27, 2009
  20. jasonbe

    jasonbe New Member

    Joined:
    Sep 18, 2008
    Messages:
    346
    Likes:
    1
    I was thinking about how many possible locations might be identifiable for a given number of game pieces, and how this number of locations could be reduced if how pieces were drug rather than disconnectedly relocated was analyzed - or if the signals communicating locations were timed. I think that a part resembling a sheet could make this project worthwhile, however the resistive properties do not have to be inherent in the sheet – these properties could be an attribute of something else such as the coatings that were suggested earlier.
     
    Last edited: May 27, 2009
  21. dknguyen

    dknguyen Well-Known Member

    Joined:
    May 6, 2006
    Messages:
    6,668
    Likes:
    64
    Varying the way you measure resistance between the contacts still doesn't resolve the fact that multiple pieces can be positioned multiple ways to get the same resistance reading becayse all playing pieces still influence each measurement all at once.

    Neither does recording the resistance and position of playing pieces in various combinations because all playing pieces still influence each measurement all at once. By the way, there's no difference between dragging a piece across the board while taking measurements or placing it on the board at a slightly different location each time. You can only take discrete measurements at discrete locations, whether or not the playing pieces are moving continuously across the board. Besides, you wouldn't be able to drag it anyways since you would need to let the piece sit still to get an measurement of it's position before measuring the resistance. It's still going to produce a discrete reading either way. The only difference is how far apart on the board each measurement is being taken, and making the distance very small or very large does not solve the core problem:

    All playing pieces still influence each measurement all at once. If you can't find a way around this, it's not going to work.

    Might I also point out that if you did try to record all position-resistances for just 2 playing pieces and you divided the board up in a measly 10x10 grid or 100 locations, there would be 9900 possible combinations all of which you would have to move through? Increase the number of playing pieces or sectors by any amount and that combination will sky rocket even more. Of course, none of this would change the fact that more than one position is going to give you the same resistance readings.
     
    Last edited: May 27, 2009

Share This Page