using a draw wire sensor and cost

Discussion in 'The Projects Forum' started by sully1071, Feb 17, 2012.

  1. sully1071

    Thread Starter New Member

    Nov 8, 2011
    Im carrying out a project where i need to find velocity and acceleration of a horizontal motion, the movement of the sensor is limited so an LVDT cant be used. Im looking at using a draw wire? But im not familiar with them.

    Can you use a draw wire to calsulate velocity and acceleration?

    Any help is appreciated..
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    Might be able to help if we knew what a draw wire is??
  3. luvv


    May 26, 2011
    From what i can find its just a rotary encoder w/ a pulley attached.

    Looks like it could be used to do what you wanted tho they look a bit pricey.

    Don't know what sort of accuracy you need but there are plenty of homebrew encoder ideas out there.

    Think the issue would be software to interpret and graph the data.

    It would seam a person could just use a hall effect sensor to send pulses to a PIC where they could be counted and graphed .

    Then it's just a matter of diameter of the pulley vs. RPM for velocity.

    And pulse width for acceleration.

    Think there is some engine dyno software out there that is specially suited for dealing w/ that kind of data but it Can't be discussed here.

    Just my 2 cents ...

  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
    Tell us more about sensor movement, & definition of VLDT. A series of beam break detectors is cheap & can be supplied to a PIC or via hardware
  5. hgmjr

    Retired Moderator

    Jan 28, 2005
    Here is some information at wikipedia on draw wire or string potentiometer.

    It may work for your application. We would need more details to advise you properly.

  6. Bernard

    AAC Fanatic!

    Aug 7, 2008
    Thanks, hgmjr,you killed two birds with one stone. I designed & built a " draw wire " back in 1958, & did not know that was what it was called. Was part of gama ray well logging unit; measuring wheel was one ft in circumference driving a chart recorder. Probe was lowered & raised with an electric wench holding 2500 ft of 1/4 in cable.
  7. Ron H

    AAC Fanatic!

    Apr 14, 2005
    Electric wench.

    Sorry, Bernard, I couldn't resist.:D
  8. Bernard

    AAC Fanatic!

    Aug 7, 2008
    I'm afraid that she would have upset gama ray readings.