Shop OBEX P1 Docs P2 Docs Learn Events
Help with reading POTS bs2sx — Parallax Forums

Help with reading POTS bs2sx

dufflingduffling Posts: 73
edited 2005-03-17 15:20 in BASIC Stamp
Im reading a POT using RCTIME , but i find the reading jumps around a bit as its taking the measurments ,

will reading a POT thru an ADC such as the ADC 0831 be a better approach?

if anyone has a link to a good place i can see some code or digarams using this chip it would help a lot..

thanks.
·

Comments

  • BorisBoris Posts: 81
    edited 2005-03-16 13:58
    Don't mean to sound mean but have you looked at the datasheet for this component?
    http://cache.national.com/ds/AD/ADC0831.pdf
    It should have just about everything you need to work with it.
    Readings using RCTIME just w/out ever touching the POT? How bad are these fluctuations?
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2005-03-16 15:43
    duffling,

    It is normal to have some fluctuation.....If your fluctuation increases as you move the POT,
    then it sounds like just a noisy POT as the wiper moves across the resistive element. This
    can vary with the quality, age, temperature, humidity, and manufacturer of the POT.... And
    I'm sure I missed a few.... One thing you can do to "smooth" out a noisy POT is to place an
    additional capacitor in parallel with the resistive element of the POT.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Beau Schwabe - Mask Designer III

    National Semiconductor Corporation
    (Communication Interface Division)
    500 Pinnacle Court, Suite 525
    Mail Stop GA1
    Norcross,GA 30071
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-03-16 19:15
    Depending on how your POT is connected to the pin for RCTIME, you can have weird readings, especially at the upper and lower ranges of the POT, due to the way RCTIME works.· Perhaps an ADC would be a better solution, but will use 3 pins instead of 1.



    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage

    Parallax Tech Support
    csavage@parallax.com
  • dufflingduffling Posts: 73
    edited 2005-03-17 06:07
    Great , actually i did read the data sheet for the ADC , i was just wondering if it will smooth out my POT fluctuations

    my Pot is returning values from 0 up to about 4000 , and its jumping +-600 at times ..... cheap pot? ,not sure
    but your suggestions are most helpful ..

    thanks again.
    ·
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-03-17 14:18
    If your values are jumping around that much I would indeed suspect a bad pot.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Jon Williams
    Applications Engineer, Parallax
    Dallas, TX· USA
  • KenMKenM Posts: 657
    edited 2005-03-17 15:20
    I also suspect the same that Jon Mentioned.

    One suggestion that might help isolate the problem is to remove the pot after you are getting the erratic readings. Measure the resistance, replace the pot with a resistor value that is close to the pot reading.

    Do you still get erratic readings. With a fixed resistor the readings will not be 'rock solid' but close to it.
Sign In or Register to comment.