Fluid/liquid level sensing solution ?

[scorpioz]

Sending a light beam through the liquid would be ok if the liquids weren't potentially opaque, like Bailey's Irish Cream. Also, the color of the liquid may give you problems. For instance, if you use a red LED and try to beam it through creme de menthe (which is oftentimes green) the red light could be optically filtered out.
JB

abt hyedenny's idea ==

well the idea would still work, we place the ir receiver to receive the signal from ir transmitter when the bottle is empty and to give a HIGH. Then we put the full bottle and ir is either blocked by the opaque liquid / refracted and does not reaching the receiver/ is weak because of coloration of liquid etc...in general will always be less than the signal that would be received if it is empty and a simple comparator circuit would do what we want. HOWEVER hyedenny the problem is that we would require to adjust the values everytime when we use different alcohol bottles. Because the bottles will also be colored/will have different thickness of glass etc.

Thinking about this now i think what i need to do is just place the ir transmitter and receiver at a small distance apart on a vertical bar that is originating for the bottle cap.
We set the comparator value by just find the value for air. (empty) and then put it in a liquid it will have some different value and once the bottle is empty the high could be noticed. the value of ir in air will be same for all the bottles as there is no glass /liquid/variable involved.

the only thing we would be looking for is any change at the receiving end. This just came to my mind as i was typing this post about how it is not possible.

Following up to this idea, i will go and search for ir transmitter and receiver. are they available premade and small and are they cheap ? hopefully ...will update if/when i find them.

possible concern, how big is the receiver and what about the power going into the receiver ...is/will it be safe to be having a receiver in liquid

thanx[/quote]

 

[hyedenny]

A emitter and detector both look like a clear LED. They cost about the same too. You can get them in different packages also.

https://www.fairchildsemi.com/products/opto/ir/index.html

 

[scorpioz]

hi

thanks that looks like what i wanted...

https://www.fairchildsemi.com/ds/MO/MOC70P3.pdf

points of concern...

[1] The distance is very small b/w the emitter and receiver. I think if there was a transparent liquid such as water present the receiver would still turn on ?

[2] I am not sure if this is right (i am trying to verify it right now) but do you think that the output will be variable ? Coz to me it seems that if certain amount of infra is received it will turn on the receiver...like receiver will either be LOW or HIGH. I would prefer to get variable voltage on the receiving end. That way i would check the voltage with air (say its 2.35V). Then i put the liquid in and i will get a value less than 2.35V ...and i will hook up the circuit to comparator. As soon as the value goes above so... 2.3V i would turn on the alarm for EMPTY bottle.

can anyone verify/inform me as to how it will work. If it only has a state of either ON or OFF then ...i would not be able to use it ... as it will be possible to receive the signal the thing is in water.. ??? I am not even sure if my concern is right. Will the receiver still turn on if both transmitter and receiver are in water..(the infra ray will not have a change in medium and there would be no refraction) but will the ir just get dispersed in water or will it still receive. The distance is very small i think and it will receive.

thanks

 

[scorpioz]

also before i go thru with this design can anyone tell me if it IS or IS NOT acceptable to be beaming this infra through a beverage which is to be consumed...?

 

[justDIY]

was the capacitive sensing chip abandoned due to high cost? (qt301)

that really seems to be the ideal, as in, doing what it's designed to do, solution... especially since it can give not only a full/empty reading, but also a linear repersentation of how much liquid remains

 

[scorpioz]

hi justdiy

the potential solution with QT301 was never tested...

**broken link removed**

the reason is that i am not sure how it works... I think you or someone else had pointed out not to be running current through the solution and I am not sure how the qt-301 chip actually works....it does need to send some burst signals and i am not sure what those signals are...

if you can please look at it and confirm to me that it is a safe solution than i can go through with that....

And i think our concern was that we would hv to program it for empty and full capacitance...but now i looked at the datasheet and it does not seem to be a problem....

Also with it everything will be measurable right ? (like colorless drinks/dark colored drinks etc...

the project is due the last week of april ..
we showed the current design and the only thing that the instructor said
was about electrodes and we told him we can use food grade stainless steel and he said thats ok use copper and in report mention that final product would use food safe electrodes...
but i thought the ir solution seems simple and possible.

thanks

 

[justDIY]

well - there is not a lot of time left then!

according to the qprox folks, the sensor can be external to the vessle or something like an insulated rod (ie, a piece of wire inside a plastic tube) placed into the liquid.

think of the sensor probe as one plate of a capacitor, and the liquid as the the dielectric, and then the earth as a another plate of the capacitor

so the sensor builds a charge on the probe (the pulses) and then times how long that charge takes to dissipate in relation to the earth. As the amount of liquid changes, the time to discharge that stored charge will increase or decrease (depending on the dielectric properities of the liquid).

qprox explains how to sense liquid levels using the qt301 right here:
**broken link removed**

there is also an older chip, which may or may not still be available, the QT310 which presents basic ON/OFF or what they call set-point sensing.

 

[The Mad Professor]

Sometimes the simplest solution is a switch.

A container has mass, and this changes depending upon the amount of material it contains wether it be liquid or solid. Resting the container upon a spring (or a similiar mechanical arrangement ) with a microswitch underneath works for a variety of industrial applications. Also has the added benefit of being non invasive ideal for food and beverage applications.

 

[justDIY]

Sometimes the simplest solution is a switch.

hey, yea, I like that idea

most booze bottles, despite being different shapes, should all be comprised out of similar amounts of glass, seeing as they all hold 750ml (at least in the States) ... I don't know about the density of one booze compared to another (for example a booze with a high water content would have higher density than some high-proof rot-gut) ... should be able to overcome that variable easy enough

 

[hyedenny]

"AllVoll" mentioned the weight switch early on in this string. Not very interesting, but definitely simple and accurate!

 

[scorpioz]

hey guys seems like the hardware guy is contend on using the current design because of time constraint. Still thanks for the help and looking at the support on these forums, I might actually do some DIY projects
(computer mods )

anyway...i will add pics of our project....and maybe some software screenshots...

I will also keep an eye on this for the last two weeks ...to be able to present more alternatives during presentation.

About the weight thing...here is the current design..the bottle are being hung upside down on coat hangers!! i dont knw where i can place the sensor etc...but neway the hardware guy is not going to change it neway. He did say he will try to mock up the ir led/receiver with descrete parts and if it works we can demo that on only 1 bottle.... 15 bottles will have the current design...

thanks for the feedback
-sz