measuring jug for the blind

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

hi chris. i was given this topic 'innovations for special people' for my project.i picked up this idea from this product,

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.

product,

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

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:

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

.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

Yeah, but will it be accurate when measuring out liquid nitrogen? BFt

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

Yukio YANO

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

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

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.

Good Luck,

• * * Christopher

Temecula CA.USA