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Fluid/liquid level sensing solution ?

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scorpioz

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hi

to complete my electrical project I need to get some feedback from
the beverage containers.

I am only looking for -NOT EMPTY / EMPTY signal, meaning i do not want to know exact amount of liquid present.

I was researching and found QT114 IC but I was unable to order it because it was being sold in minimum 50 quantity and I am not even sure if it will work.

I need around 20 of these sensors. My alcohol dispesing machine is currently made so that the original alcohol bottles maybe used by inverting them and only putting a special cap on them. So I am looking for any solution that i can use that will work with any bottle ?
for example an IR transmitter and reciever will not work (i think) because of having different shade/thickness of glass/label position on bottles.

The cap that i am using, I can actually put some probe etc through it so that the inside of the bottle can be accessed.

Earlier I used a conduction method where I had two probes and 5V was attached to them and when there was liquid there was small current flow but when liquid flowed out the voltage changed /(on comparator) and high was received. However this was objected to by the teacher on the grounds that some beverages may not conduct ? / It might not be FDA approved to pass current through the beverage.

The idea i have used right now is to use two contact and have a floating steel ball, and when it comes down as liquid flow it connects the two contacts and current flows...(again i will hv to defend that it is safe to do so)

So any suggestions guys ?

IF we have to stick something through the bottles (right now for display we are using 20oz water bottles). I would do it as a last option, to make a hole on the side of bottle to put something like a float switch etc.

so what will work, i dont think ultrasonic would reflect off the surface ? and even if it does i would need microcontroller/ microcontrollers and program them to altert etc.?

so any suggestions /help
if you know any websites where I can buy QT114 IC from right now...i need 2-3 to check if it works and then around 20. (so site that are offering bulk are not an option)....Will the QT114 IC EVEN WORK ?
which ICs /sensor (infra/ultrasonic/proximity) would work ?

pleasssssssssse help

thanks in advance.
 
Well scorpioz,
earlier today, on another board, I recomended some one to look up the QT300, which is similar, but perhaps newer. I got mine from http://www.SAMPLE.co.kr but when I checked later, had trouble finding any components on his site. I think they are still in the store, but I recall they were a bit pricy, although I don't recall just how much. I think this is the best way for you to go here. I would think these sensors are available somewhere. Try futurlec.com, they may have something, and if not, you could become a member of Spark Fun's site, and make a recomendation that they carry this chip. (I would back you on that one, and may even suggest it to the boys over there, myself.)
Let us know how you make out, and the next time I bop off to the city, I'll check out sample's store, and at least get an idea of what he sells this chip for. There is also a chance I could find a cheaper source here, but my Korean is not too good, so I am somewhat limited.
Regards,
Robert
 
Hi,
The QT301 (similar to he QT114, but 8 bit instead of 16 bit) is available from DIGIKEY in quantities of 1.
 
how about a reed switch, on the outside of the bottle, near the cap.

inside the bottle, you put a small magnet coated in wax, so it floats and is food safe.

when the liquid level is low, the magnet will sink down near the cap, and the reed switch will sense it

could use a hall effect sensor too, whatever you can get ahold of.
 
I believe that a stud sensor works on a principle similar to the QT114. They are pretty cheap. Even if they work, would your instructor allow you to use one, or the guts from one?
 
hi

thanks for all the replies (quick ones at that too)
i read them and have been discussing the solutions proposed by you guys

qt301-d looks like a good one...i'll be ordering 2-3 of those and check it out how well it performs. About using the stud sensor, on the page it takes it just says that it use a small radar to sens the different capacitances and therefore when stud is found the capacitance changes. Why did you say will the teacher allow it or not ? I don't see anything that he can object to ?

thanks guys,
but until I am done with a working model keep it coming
i can use as many different ideas/sensors/approaches as possible.

thankx
- sz
 
scorpioz said:
About using the stud sensor, on the page it takes it just says that it use a small radar to sens the different capacitances and therefore when stud is found the capacitance changes. Why did you say will the teacher allow it or not ? I don't see anything that he can object to ?
I thought maybe you had to design a circuit.
I haven't used the type that uses radar, but the I know that ones that sense dielectric change are pretty effective, and seem like they might work in your application. The radar units might work as well. Or maybe neither would work.
Please let us know what solution you use.
 
I will post which IC i used and how well it works (if i get it to work :eek: )

right now I have ordered another IC ..the number of which I dont remember off the top of my head, but it was not QTxxx it was some other IC i found online...

About designing circuit not really, the project we proposed was an alcohol/beverage dispenser. We have succesfully tested our software and simple hardware to dispense (using solenoids to open and close vacuum lines going into the bottle.)

So one important part of the project is to have a warning/prompt/alert or something on the software screen that can say bottle cannot be dispensed because it is empty.

If no such feedback is made, then the software operator will not know if drink was actually dispensed or not (and the software soft counters would be misleading because there would be no actual dispensing).

The project was our own proposal, so we can flex on using any type of setup/software/ics etc.

As i stated above right now we are making it so that original alcohol bottle can be used by only placing our cap. If however the empty sensor gives us too much trouble we might just go ahead and buy big square empty tanks and drill the level sensors (like float sensors) in it. Or use infra sensor as we would know what value will be received if its empty.

hopefully we can find some solution to do it without changing our whole idea.

project is due around first week of May 06 :(

Thanks for the support.
I am also looking at QT-301 chip incase our current one does not work.
 
Have you thought of using the weight of a full container versus the weight of an empty container as your trigger? Such a scheme should be easy to construct and blend nicely with the electronics of your project.
 
hi guys

just to update you, we got the following IC to work perfectly for our needs.

https://www.allelectronics.com/cgi-bin/item/L4620/search/LIQUID_LEVEL_ALARM_IC_.html

L4620,

It is hooked up almost like shown in the data sheet only difference being that the pins 2/3 are together with a pot going to ground. it is operating at 50hz right now and it is programmable using external R/C components.

Yet to be integrated with rest of the software etc, the ic works well and once the bottle runs out of water it turns a blinking led on.

my next ic would hv been qt301 or similar but now it works so...no need

thanx for all the help

oh about the last post about using weight/ that is going to be very very hard as we do not know the shape/weight of alcohol bottle and a low density liquid would present problems. As I said in the begining we are currently using the original alcohol bottles / meaning they maybe big small thickness of glass can be different, shade of glass can be different and label placement on the bottle is also unknown (variable) ...so pretty much IR is out of question/weight dependent sensor also.

thanx for the feedback though.
 
The L4620 is an integrated circuit, designed for the liquid level control in automotive applications. The liquid level is indicated by an attenuation between transmitted and received signal across a sensor tip in the liquid.

Metal probes, inside a food product?! I can tell you that would never pass a health inspection... unless you're using food grade stainless steel ... and I think the effects of the current running through the probes would still cause ion migration, leeching who knows what into the liquid. Not to mention having electrical probes inside a potentially INFLAMMABLE bottle of alcohol... that should make any fire inspector very happy.

Please, go back to the drawing board and come up with a real solution, which is capacitive discharge based sensing :)
 
justDIY said:
Please, go back to the drawing board and come up with a real solution ...
Before you say something like that, maybe you should read the post just prior to yours. It says...
scorpioz said:
... just to update you, we got the following IC to work perfectly for our needs.
JB
 
I stand behind what I've said

first, the major problem ... electrical probes inside a sealed container with an inflammable liquid (OP mentions alcohol several times). sure its low voltage, but can anyone be 100% sure some sort of surge could not make it through, to the probes, igniting the liquid and causing an explosion that could lead to injury or loss of life.

second, a minor problem ... the probes are using AC, to avoid electroplating and deteriation of the probes, however, some ions will still migrate from the probes into the liquid ... be it water or alcohol, it will be contaminated by this. who wants their scotch on the rocks contaminated by heavy metals?

The OP also suggests they knew electrodes in a solution would not be safe

scorpioz said:
However this was objected to by the teacher on the grounds that some beverages may not conduct ? / It might not be FDA approved to pass current through the beverage.
The idea i have used right now is to use two contact and have a floating steel ball, and when it comes down as liquid flow it connects the two contacts and current flows...(again i will hv to defend that it is safe to do so)
 
I'm not disputing any of the points you've made about hazards, etc. However, when the o/p said that the chip he has works "perfectly for our needs" it seems to me that the discussion pretty much ends there. It's evident to me that this is a project for school, proving his concept and earning him a grade in design class. I don't get the feeling that it's something they're planning to market, thereby requiring approval of federal, state and local authorities. When a project (or portion thereof) of mine works the way I want it to, I move on. I don't go back and redesign it if I don't have to.
JB
 
hi

first off yeah i thought i was done with this posting neway...
yes we can use food grade steel conductors in the liquid....

About the second problem here is why I went with it...
after researching quite alot ...i found some small sensors..they are shaped like a bolt ..i dont remember which website/link i saw them from. In its data sheet said that the sensor has two contacts separeted by some plastic (think of a headphone jack), and they were using an ac voltage to pass throught it and measure the changes. I do maintain your point of view on the issues but in the data sheet it ssggests alot of uses...including stating that its safe for Beverages/ (it does NOT mention alcohols or inflamable liquids as exceptions and personally when i hear the word beverage i think alcohols? ), it also said it is safe for medical fluid sensing (i am thinking that if it is safe to use it in medical fluid sensing like blood/medicine then it is definitely safe for use with alcohol?)

Also in some extra advertising if you may/ it showed the probe (again think headphone jack) with the +v and -v appearing on it and they had four successive pictures and the +v and -v were switching between the two probes. This they said helped to neutralize any kind of ionization that may take place.

like u correctly quoted me in your reply regarding instructor questioned us during our presentation last time we presented it (we were using DC)...the only thing i can do is print the data sheet out for the other one and present that as proof that it is allowed to do so..?

p.s. the deadline is approaching (last week of april) so if u have any suggestions that might be applicable to quickly resolve this issue (without having to go back to the drawingboard) they are most welcome.

another p.s. I am actually not personally responsible for this fluid sensor issue (any hardware infact)...I am doing the software..but I just looked up some ICs to help out the other guy in my project...coz i did not quite like his DIY stuff... (putting steel ball in the bottle...then making it float using closed straw piece and then finding out it hits the contact only <20% of the time was not as comforting as this current solution. And even though we will be graded mainly as a group, member can get different grades, i might suffer a grade if the project messes up in the hardware also even though i am not doing the hardware at all.

thanks for the feedback...
 
oh and there was some mention about the ions that are discharged in one cycle are neutralized in the other cycle or something like that..
 
Hi,
Congrats on your circuit. The idea of any ionization being "neutralized" by the use of AC current is wrong though. Any dissociation that occurs on one pole of the probe will just occur on the other pole when the AC cycle is reversed. Also, the fear of any alchoholic beverage (or gasoline for that matter) igniting from passing these kinds of currents through it is absurd. One could immerse mains voltage probes into barrel strength bourbon and the only thing youd lose is your wager that it would ignite. Pure ethyl alcohol is a nonionic compound, and the rest of the volume of booze is mostly water, which barely conducts.
 
hmm, well i searched moe yesterday and i found a very good solution,

**broken link removed**

it is a bolt shaped form and has an IR transmitter and receiver placed in it and it is reflecting off the angled walls and according to the website it changes states when liquid is present coz ir is dispersed etc :S ?...

neway the only downside to all these solutions is that they cost $50+ for one and i need 16, and i am not really wanting to put so much money for this project, specially since right after i am done with the stuff it is useless to me.

So if any can find any type of sensor solution which is

1. can be mounted from bottom... (not side/top)
2. is food safe
3. is small
4. is cheap

the ir sensor above can be mounted from bottom, is food safe and small but is not cheap.

then please do post...i am keeping an eye on this forum to benefit from any ideas that are being posted.

thanx
 
thats a great idea!! Cool... You might be able to make one that operates on the same principle taking advantage of the refractive index of liquids. Maybe aiming a LED at an angle through the bottle at the neck to a detector on the other side. When liquid is there, the light would be bent at a different angle than if no liquid was there.
 
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
 
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