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measuring jug for the blind

Discussion in 'Electronic Basics' started by mimet66, Mar 11, 2007.

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  1. mimet66

    mimet66 Guest

    hi all!
    my project is to build a measuring jug for the blind.this jug can sense
    certain water level for example at 250ml,500ml etc using some kind of a
    sensor.i'm thinking of using an existing kettle with little floating thing
    that tells the water level.but i don't know what suitable sensor to use to
    detect this floating thing.i'm thinking of using infrared sensor.when the
    floating thing passes the sensor at certain level,it will make sound.
     
  2. Chris

    Chris Guest

    Liquid level can easily be determined by attaching a float to a dancer
    arm, have the dancer arm turn a potentiometer with a reference voltage
    applied, or by connecting it as a rheostat, applying a reference
    current, and then reading the voltage.

    If you want to visually detect the position of a floating object,
    you'd probably need an array of LEDs in a line, and float level would
    be dependent on which was the highest one that was off.

    You could also use ultrasonics to determine the distance of the water
    level from the ultrasonic transducer.

    However, each of these has a basic flaw -- it's difficult to have
    something in the jug without being able to clean it. Much more
    trouble than it's worth.

    As a practical matter, this is usually either done by weight, or by
    tapping the jug and listening for the tone (which will rise as the jug
    becomes more full).

    If this is a school project, you might want to describe in some detail
    what the class requirements are. It's possible you could hone this up
    into something that might get a good grade.

    But as a practical matter, I'd guess there isn't a lot of potential
    here.

    Good luck
    Chris
     
  3. mimet66

    mimet66 Guest

    hi chris.
    i was given this topic 'innovations for special people' for my project.i
    picked up this idea from this product,
    http://www.cobolt.co.uk/cobs/product.asp?dept_id=2&pf_id=Jug

    i prefer using the visually detect the position of a floating object
    method.my kettle has this floating object at the side to indicate water
    level.so i have to put sensors on the outside of the floating indicator.i
    think this method does not need any device at the inside of the jug.

    how about the electro-optic type sensor?is it expensive.i found it on this
    site.
    http://www.gemssensors.com/content.aspx?id=282
     
  4. Chris

    Chris Guest

    This little ASCII diagram shows the idea behind the Gems opto sensor
    you link (view in fixed font or M$ Notepad):

    |
    | Photo
    | | Trans.|
    | | LED - -|
    | | ->|- \ ^ |
    | | | --- |
    | | | | |
    | | V | |
    | | | ^ |
    | | | | |
    | | | | |
    | | | ^ |
    | | V | |
    | \ | | /
    | \ | |/
    | \'-->--'
    | \ /
    | \ /
    | \
    (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

    The LED sends light down to the apex of the cone. If there's no
    liquid on the plastic, nearly all of the light will reflect off the
    inner surface of the cone, and bounce back to the phototransistor as
    shown (kind of -- sorry, this is a newsgroup ;-). However, any liquid
    will change the optical characteristic, causing most of the light to
    go through the clear plastic cone into the liquid. Hence, level
    detect.

    Now, in order to use this scheme, you'll need several of these
    sensors. In addition, these are not rated as food-safe, which means
    you can't sterilize the surface without damaging it. Gems makes some
    other sensors which will do the job, but they're significantly more
    expensive.

    If you're trying to do opto level detection on the cheap, you'll
    probably be best off with multiple LEDs and multiple photoransistors.
    You can look through a clear jug that way. By turning on one and only
    one LED at a time, and only looking at the phototransistor output
    directly opposite, you can get a clear idea if something is
    obstructing the view. And all of the LEDs plus all of the
    phototransistors shouldn't cost more than one of these Gems switches.

    Looking at the device you linked in the Cobolt catalogue:

    http://www.cobolt.co.uk/Catalogue2006.pdf

    I get the feeling that it's actually a scale. Note that you have to
    calibrate it for different types of liquids, and it's also capable of
    measuring solids with user-defined functions. This seems to be the
    easiest way to "skin the cat", and I'm fairly sure it's the method
    they use.

    If you wanted to do this, you'd have to build a scale around a
    removeable jug in such a manner that it was watertight, the jug would
    rest freely on the scale base when it was resting, and also that the
    jug would be removeable for easy cleaning. Not so difficult to put
    together, if you've got access to a microcontroller development kit.
    Also, the "talking" function could be done with one of the ISD talking
    chips without too much difficulty.

    Now for the hard part -- fess up. This is a school project, no?
    You'll get better advice if you can be clear about what you need.

    By the way, it's almost midnight in this time zone -- if you need a
    response, I'll try to post again in about 6 or 7 hours.

    Good night
    Chris
     
  5. Yukio YANO

    Yukio YANO Guest

    ..my kettle has this floating object at the side to indicate water
    This is supposed to for a BLIND individual !!!

    The Answer is a Top Loaded Balance or Weight Scale with an Audio
    Read-out with a Tare mode

    With a Maximum of 5 Kg./10 pounds, sensitive to 5gm./0.1 ounce

    In Use: You would Tare or Zero the Scales to the weight of the Jug or
    container then fill until it sounds right, then confirm the "Fill" by
    re-weighing the container and measure the weight by "Hearing the
    Readout". Or just pour the liquid being measured into the jug and listen
    to the Read-out as the liquid is being dispensed .

    Yukio YANO
     
  6. With a Maximum of 5 Kg./10 pounds, sensitive to 5gm./0.1 ounce

    Yeah, but will it be accurate when measuring out liquid nitrogen?
    BFt
     
  7. Yukio YANO

    Yukio YANO Guest

    I don't see any problems, Yes I have used Liquid Nitrogen on several
    instruments for several years.

    Yukio YANO
     
  8. Grey

    Grey Guest

    I have seen commercial units for this exact purpose. The unit is in a small
    box/enclosure which hangs over the side of a cup with two wires. Water
    conatct, closes circuit, buzzer rings. I good design would be to have AC
    voltage on the probes to prevent plating with time. Similar units are used
    for bath tubs, sinks etc.

    Graham
     
  9. Rich Grise

    Rich Grise Guest

    How about a float with a stick on top, through a hole in the top of the
    jug, (a la hydrometer) that the blind person can "sense" by simply feeling
    it?

    Admittedly, it's not very electronic or hi-tech, but shouldn't the first
    question be, "What works?"

    Good Luck!
    Rich
     
  10. christopher

    christopher Guest

    Hello,

    I found this piezo-resonant fluid level sensor in a technology
    magazine I received today and remembered your post. It could give you
    ideas even if you don't buy one.

    http://www.gemsmedicalsolutions.com/template.aspx?id=36

    Good Luck,

    * * *
    Christopher

    Temecula CA.USA
    http://www.oldtemecula.com
     
  11. jasen

    jasen Guest

    It may be possible to cause air to blow across a "penny-whistle"
    that's tuned by the water level instead of a manual plunger.
    the pitch of the sound will indicate the water level.

    A filling tube that extends to the bottom of the jug may be all
    that's needed, if it's rigid enough you should get the "bottleneck filling"
    sound as water is added, again the pitch of the sound will indicate the
    water level.

    Another option would be regulating the flow rate of the water so that the
    user merely has to count eg. five seconds for each cup.

    I find I can judge the level of fluid in a spray can fairly well just by
    sloshing it

    Bye.
    Jasen
     
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