Digital counter and data logger

Discussion in 'The Projects Forum' started by ayorabi, Apr 28, 2014.

  1. ayorabi

    Thread Starter New Member

    Apr 28, 2014

    I am currently working on a device that measures water level in

    wells. Basically the water level movement is translated to the

    surface via a rope. On the surface the rope is wound on and off a

    reel as the water level changes. To measure and log the reel

    rotation and subsequently the water level movement, I thought I can

    add certain objects on the perimeter of the reel and install a

    digital counter the counts the number of these objects that are

    passing in front of it as the reel is rotating. The counter must

    also recognize the direction of the rotation, and I should be able

    to log the output of the counter to a memory card against a time


    I found many devices in the market that does that and much more,

    however I'm really looking at cutting down the cost as much as

    possible. Therefore I'm seeking your advice on the best way I can

    build/buy this circuit. I would also appreciate an indication on the

    cost associated with your suggestion.

    Many thanks in advance,
  2. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Counting has issues. You need to get the count direction right, and you also need to index against some start or end location every time it is turned on (which might be hard to do in a water tank).

    You are better off with an absolute position sensor, not a relative one (like a counter).

    You can wrap the rope around a potentiometer shaft and measure the pot voltage. Or around the shaft of an absolute position encoder. But that is more expensive.

    For measuring wells you can use an off the shelf ultrasonic distance measuring module.

    Or if you are fixed on the idea of dropping a rope and float down wells with all the reeling effort etc, maybe you could hook a rope and pulley up to a mechanical rotary counter?

    Or a $4 bicycle computer that counts distance, which already comes with magnet and sensor, and display. :)
  3. MrChips


    Oct 2, 2009
    or you could measure the water level with a chain, rope, dipstick, ruler, barometer, stopwatch, thermometer, etc., etc. Choose your method, as in The Barometer Story.
  4. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    Depends on what your cost limit is. Installing an of-the-shelf quadrature encoder on the reel and a datalogger could be under $100.

  5. wayneh


    Sep 9, 2010
    Can we assume (only) battery power is available?
    How much data will be collected between dumps; how long does it need to run and what is the sampling frequency?
    What form do you want the data in - USB thumb drive, hard drive, strip chart, etc.?

    A graduated rope, like a tape measure, is a viable option. I've used something like it. You could even use a webcam to put the rope online and you could read it from anywhere as often as you like.

    The length of a rope varies with moisture and other variables, so precision is a problem.