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Sensor

TumblerTumbler Posts: 323
edited 2008-12-12 05:21 in General Discussion
Hello,

I want to measure the volume water in a tank.
I have tried some methods (see picture)
But i want to know if there is another solution to get this work wih only 2 wires.
What i want is a value from 0 (empty) to 100 (full).
I have seen an article with the ping))) but i want to use the ping for it [noparse]:)[/noparse]

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Comments

  • remmi870remmi870 Posts: 79
    edited 2008-12-08 09:59
    they do make fuel tank sensors that have a steel pipe that a float rides on and it reads back resistance in the wire, this resistance can be used to feed back your level via gauge or into the bs2. just google it, if you are looking to use your own meathod or "homebrew" sensor, then i would look into maby using a potentiometer and a strip of metal twisted, you attach the float to the twisted piece of metal and as the water goes up or down, it will spinn the piece of metal (kinda like a archamedies screw) and change the resistance, same concept. the only other option is to use a floating arm with a potentiometer. I guess you need to clarify how you plan to send the signal.
  • Carl HayesCarl Hayes Posts: 841
    edited 2008-12-08 15:03
    Another way would be to use a pressure sensor at the bottom. How deep is the tank? The depth would determine the presssure at the bottom.

    Yet another way would be to use a potentiometer with a float mounted on an arm. The float rises, turning the shaft of a potentiometer (or moving a linear pot directly), and the resistance changes. Many automotive fuel gauges work that way.

    Another way would be to use, say, an ultrasonic distance-measuring device to measure the distance from the top of the tank to the surface of the liquid.

    Another way would be to reflect a collimated light beam from the surface of the liquid at a row of photoresistors on the far wall. Seeing which photoresistor was illuminated would allow you to know the approximate depth.

    If the liquid is transparent but colored, another way would be to put a mirror on the bottom and shine a light onto the mirror, which would reflect it back to a photodetector mounted next to the light source at the top. The light would go down through the liquid, bounce off the mirror, and come back up to the photodetector. Its intensity would be a measure of the depth. The shallower the liquid, the brighter the returning beam. I once designed a colorimeter that way. It measured, not the depth, but the color density of the liquid, which was diluted human blood -- we were actually measuring the hemoglobin concentration (the darker the liquid, the greater the hemoglobin concentration).

    You could, instead, use a load cell to measure the weight of the liquid. You could design your own, using a spring and a linear potentiometer.

    A little brainstorming would probably lead to ten or twenty additional approaches.

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2008-12-08 15:09
    This thread is off topic (not BASIC Stamp related) and is being moved to the Sandbox Forum.

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    Chris Savage
    Parallax Engineering
  • LeonLeon Posts: 7,620
    edited 2008-12-08 18:43
    You could use a manometer with a float and detect the float height with optical sensors.

    Leon

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    Suzuki SV1000S motorcycle
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2008-12-09 04:16
    Tumbler,

    How big is your tank?· ... A capacitive sensor·usually works well.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • TumblerTumbler Posts: 323
    edited 2008-12-09 05:35
    The tank: about 25 x 15 x 20(height) cm
    The water amount is +- 10 cm, and thats the maximum.

    I need it to automate a humifier.

    Beau, a capacitive sensor?

    I will try the idea of Remmi (with the potentiometer strip) ·later this week.
    ·
  • Carl HayesCarl Hayes Posts: 841
    edited 2008-12-09 18:56
    If your underlying problem is to keep the tank from running dry, you could use a float valve with no electronics at all. Every automotive carburetor has one, and so does almost every flush toilet. The ones used in Scotsman ice makers are simple, self-contained, and not very large, and come in an assembly with a small reservoir. But the ones used in flush toilets can be bought in every home-supply store such as Home Depot or Lowe's or Scotty's.

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    · -- Carl, nn5i@arrl.net
  • BeanBean Posts: 8,129
    edited 2008-12-09 19:12
    This is just a wild thought, but I wonder if you could measure the volume of air in the tank by detecting it's audio resonance frequency ?
    A small speaker and condensor mic, measure what frequency is the loudest. That should be the resonance frequency and you should be able to determine the fluid level from that. More water, high resonance frequency, less water, lower resonance frequency.

    Do you think that would work ?

    Bean.

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    "The welfare of the people in particular has always been the alibi of tyrants." ~ Camus
    www.iElectronicDesigns.com

    ·
  • Carl HayesCarl Hayes Posts: 841
    edited 2008-12-09 19:29
    Bean (Hitt Consulting) said...
    This is just a wild thought, but I wonder if you could measure the volume of air in the tank by detecting it's audio resonance frequency ?
    A small speaker and condensor mic, measure what frequency is the loudest. That should be the resonance frequency and you should be able to determine the fluid level from that. More water, high resonance frequency, less water, lower resonance frequency.

    Do you think that would work ?

    Bean.

    Not a bad idea, if you can separate the various resonances (one for width, one for length, one for depth, etc.).

    The way to measure it would not be the loudest sound, though.· Much better to measure the peak impedance at the transducer.· Depending on the Q of the cavity, there will be a greater or lesser peak in the impedance at resonance.· It takes many fewer parts to measure this than to measure the loudness of a sound.

    But I still think that if all one wants to do is keep a tank from running dry, a simple float valve would be easier.· Or one could just invert a bottle with its neck opening at the level one desires to keep.· When the liquid surface gets below the bottle's mouth, it goes glug and lets a little air into the bottle, and a little water comes out.· This is the method used in many water coolers (the ones with a 5-gallon bottle turned upside down and resting on top).

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    · -- Carl, nn5i@arrl.net

    Post Edited (Carl Hayes) : 12/9/2008 9:17:48 PM GMT
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2008-12-09 19:43
    If the idea is to keep the tank filled to a certain level, a pressure-operated toilet fill valve is a simple solution that can be obtained from any local hardware store. Fill level is determined by a screw adjustment, and there are no floats or ball cocks to mess with. Plus, they work even when the power goes out!

    -Phil
  • Carl HayesCarl Hayes Posts: 841
    edited 2008-12-10 17:19
    Bean (Hitt Consulting) said...
    This is just a wild thought, but I wonder if you could measure the volume of air in the tank by detecting it's audio resonance frequency ?
    A small speaker and condensor mic, measure what frequency is the loudest. That should be the resonance frequency and you should be able to determine the fluid level from that. More water, high resonance frequency, less water, lower resonance frequency.

    Do you think that would work ?

    Bean.

    A couple other thoughts:·

    (1) not only does the impedance of the speaker peak at resonance of the system to which it is attached·(speaker and cavity, in this case), but it also changes character,·from capacitive (just above resonance) to inductive (anywhere below resonance).· You could design an oscillator that would run at·resonance (using the speaker as a resonator, or tank), and·put a counter on it.

    (2) but·any of these schemes would be noisy.· Ouch.

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    · -- Carl, nn5i@arrl.net
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2008-12-11 07:32
    Tumbler,

    "Beau, a capacitive sensor?" -· Yes, check this thread out ...

    http://www.parallax.com/Portals/0/Downloads/docs/cols/nv/vol1/col/nv27.pdf

    [noparse][[/noparse]Beau Schwabe feeling old] ...WOW, was that project really 11 years ago [noparse][[/noparse]/Beau Schwabe feeling old]

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • TumblerTumbler Posts: 323
    edited 2008-12-12 05:21
    Hey *Old* Beau tongue.gif

    Looks intresting...

    But if it's gunna work with only 10 cm high waterlevel ?
    I will test it in the weekend or so.
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