For an Arduino project I am in need of a sensor(valve type functionality) that can achieve the following - it would open when a liter bottle or container is empty and close when it is filled up to be released at other end. The same process would repeat again and again.
The issue that I am facing is that all electronics valves cannot be placed inside water - is there an alternative for same?
valusoft 
"cannot be placed inside water"... I think you need to explain this. Are you saying that you cannot use a valve?
More importantly... is this yet another thread about your same project? If it is, and it sure looks like it, I am inclined to delete this and ask you to continue in your most recent thread. My head is spinning...
Ross
Moderator.
Yes, I have some other threads but this one is not related to them.
The one liter capacity bottle / container would be placed inside a water tank - so electronic valves that I am aware off needs to be placed inside water. I understand that the coil of these electronics valves would get damaged if they are placed under water.
valusoft Please draw what you mean. I still do not understand how the bottle is inside a full water tank...
awneil 
Oh no - not another thread on this topic!
At the very least, you really do need to reference all the other threads:
https://www.avrfreaks.net/forum/f...
https://www.avrfreaks.net/forum/electronic-water-dispenser
I need to measure a specific qty of water for discharge.
The design that I have though of is to make outlet tap connected to a bottle / container of 1 liter capacity inside the tank. Now when tank is filled the water the bottle also. Now I close the bottles input pipe (via electronic valve) and open up the valve at the side of tap. This is for the functionality that exactly one liter of water drains out the tap only. Now these 2 electronic valves works complimentary such that the discharge amount is always 1 liter.
I am unable to keep this one liter container outside the water level cause I want it to be filled due to gravity force (no pumps).
Yes, as per the solution stated out there - I was told to look for a design technique.
valusoft Sorry... that is gobblydegook to me without a drawing. Or show us your teacher's homework assignment paper. Maybe his words are clearer.
Goodnight.
awneil How about you have a 1-litre measuring vessel; you fill that, and then just discharge that known volume of water.
All you need to do that is 2 valves and one sensor to tell you when the measuring vessel is full:
Yes that's exactly I need to achieve. But then this is supposed to be automated or rather to be controlled by a controller. I need to keep the container inside the tank - so which valves I can use inside water? Wouldn't the electronics valve get damaged if kept inside water?
Is there any alternative apart for electronic valves?
Thanks in advance
Can you explain *exactly* what you are trying to achieve?
Would something like this work...? Open valve 1, close valve 1, open valve 2, close valve 2, repeat.
valusoft Brian,
Will you need to allow some mechanism to prevent air being trapped in the 1 litre pipe with valve 2 closed... I think.
Night all.
Ross
awneil I need to keep the container inside the tank
Why?
so which valves I can use inside water?
You obviously need valves designed to control water!
Wouldn't the electronics valve get damaged if kept inside water?
See above - part of your design is select parts suitable to the application!
Is there any alternative apart for electronic valves?
What do you mean by "electronic valves"?
The valves themselves don't need electronics - they just need to be electrically controlled.
microcarl 
This must be a Common Core version of physics, science or embedded controls design.
1. Why would you put the control valve in the inside of the supply tank?
2, Why would you put the one liter bottle inside the supply tank?
3. If the one liter bottle is inside of the supply tank, how do you connect & disconnect the fill fitting and then remove it from the supply tank?
Doing field service work for years, in the bottling & canning industries, I have seen bottles filled with carbonated liquid and beer (yes, Ross, your favorite beverage) up to 1,000 bottles per minute. I have seen cans of vegetable soup filled at about 300 cans per minute. Never have I seen where the fill valves or containers being filled while placed inside of the supply tank!
I'm thinking, some rethinking of the problem and a proper solution is in order here!!!
awneil
- 1 valve to fill the measuring vessel;
- 1 valve to discharge the measuring vessel to the "customer";
- 1 sensor to tell when the measuring vessel is full - a simple float switch should do?
Like this, perhaps:
awneil With just the 1 level sensor, it's up to the "customer" to maintain the delivery until the complete litre has been received; if they choose to stop short, that's their own problem!
You might, instead, want to have two level detectors:
awneil 1. Why would you put the control valve in the inside of the supply tank?
Indeed!
prakash_prasad wrote:
so which valves I can use inside water?
You obviously need valves designed to control water!
Something like this, perhaps:
awneil Such things are commonly used in washing machines, vending machines, etc, etc - should not be hard to find...
Another fine thread dedicated to the DOHHH?? moment
Something like this, perhaps:
http://www.adafruit.com/product/997
The valve has a gasket arrangement inside, so there is a minimum pressure requirement of 0.02 Mpa (3 PSI).
More importantly:
These solenoids are not rated for food safety or use with anything but water.
So if the application is to dispense drinking water, I wouldn't recommend them.
I'd originally wanted to use them to dispense hot water onto a tray of dry ice for a fog effect from within a prop for a corporate event, but the gravity-fed reservoir just didn't provide sufficient pressure to cause the full volume of water to be dispensed in the required time. I eventually went with a toilet tank flap valve and a servo to pull it open. WHOOSH!
Although that probably wouldn't be suitable for the OP... I'm sure a bit of searching would reveal a similar but more suitable valve.
EDIT: like this one:
http://www.adafruit.com/products/996
Unlike the plastic solenoid valve, this one does not have a gasket, so there is no minimum pressure requirement.
...
These solenoids are not rated for food safety by any official standards. However, they are made of cast brass, with a rubber gasket made of NBR (Nitrile Rubber) so it can be used with any fluid that will not damage or be damaged by the rubber gasket material.
... although at almost 4 times the price... and 10 times the current!
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Firstly, thanks a lot for all the suggestion / help as provided. Attached is the physical implementation method of my project:
The issue with flow sensor is that it does not discharges water correctly. I cannot every time do a calibration with h/w.
As I understand that I need to make use of Waterproof valves only as a solution or find a mechanism that can always make water flow control controlled despite of various PSI / water level outside it
valusoft Prakash,
I have read everyone's suggestions, comments and now agree with Brian that his suggestion is the best. https://www.avrfreaks.net/comment...
How could it be improved? Well, I would do the following.
There is no need for this to be inside the main water tank unless you want to keep unauthoriseed hands away from it all, in which case you would simply build a box around the whole assembly.
I hope that helps you.
Ross
Umm.... please correct me my understanding of physics is wrong here, but if you fill an internal 1 litre container inside the tank as you depict, once the inlet valve is closed, this 1 lt container becomes an isolated system and no longer has the pressure from the whole tank to allow gravity flow to empty its contents?
Secondly, would a similar problem exist when trying to charge the 1 lt container when the tank volume is very low?
Seems to me this method (if possible) would significantly limit the usable volume of the tank.
Steve
The filter would be at a height greater than the one liter container than the tap would perhaps solve the issue. But now I also prefer having the container outside cause these containers may impure (by rust or other means) the purified water itself if not properly cleaned for several days
You're over-thinking this; it can be done with no electronics at all - indeed, no moving parts except the water.
Use a syphon.
Just a U-bent bit of pipe inside your water container and exiting through the bottom (you'll need to seal this) with the thickness arranged to suit your flow length and the depth of the U such that there is one litre in the tank between the top and the bottom.
When the slowly-filling tank reaches the top of the bend, it will start to syphon until the fluid falls below the open end. This approach is used in self-flushing urinals world-wide and has worked for a couple of hundred years, so the technology's fairly, um, convenient.
Neil
That would be great but would no extra water flow trough syphon - would be exactly one liter. And how would water flowing from upper half to lower half would be stopped when water is getting dispensed. Please provide a figure for same it would clear some doubts. Also how would we make the water to stay inside syphon I mean how would water flow outside without additional water getting inside the syphon
Did i not suggest some time ago you needed a positive displacement pump? For example: if we get a syringe , some tubing and two, one way valves. Pull the plunger and we suck a given amount of water into the syringe. Push the plunger and we output a known amount of water. Repeat for required volume. To automate this, get a motor, gearbox and crank. Count number of rotationsto derive volume. I bet there's commercial products that do exactly this. Job done.
BTW for the product https://www.adafruit.com/product/828 I am buying a water flow control valve - please let me know what flow rate value valve I should buy. Would the device work properly after having the flow control valve fitted in the dispense pipeline before the device?
david.prentice I've used a very similar valve. The biggest shortcoming is they need a minimum pressure in order to open, and they're not a high-flow valve. Internally the valve is a diaphragm which sits against a valve seat and is withdrawn by the solenoid.
Most solenoid valves are indirectly operated. The solenoid acts on a tiny orifice in the control port. This operates the main port. e.g. valves used in mains water systems generally require 0.1 bar to operate the control port.
Directly acting valves require enormous solenoid power to operate the main port. Not only are they big, have poor max pressure but they cost a fortune.
As you have discovered, there are better ways of controlling large volumes at low pressure.
Regarding the OP's problem. It would help if he said what real-life application he wants to do. Then 'thinks' about what similar industrial application exists. e.g. filling beer bottles, soup cans, treacle tins, ...
David.
awneil valusoft's diagram (post #22) is essentially the same as prakash_prasad's post #21 - but without the nonsense of having the stuff inside the tank.
The trouble with both of these is: where will the displaced air go?
My arrangement (post #15) does not have that problem.
The trouble with the urinal-style syphon (barnacle, post #25) is that they take a very long time to fill, and they discharge immediately they are full - whether there's a "customer" ready or not! (which is why there are many "economiser" devices on the market these days)
awneil That would be great but would no extra water flow trough syphon - would be exactly (sic) one liter.
There you go again: it is never going to be exactly one litre - you have to have a tolerance on that!
valusoft The trouble with both of these is: where will the displaced air go?
Andy,
I think/hope that if the "pipes" leading from the tank are of sufficient diameter (> 1.5 inches), the imbalance will cause the air to bubble rapidly upwards through the system and be displaced by the water column.
Cheers,
Ross
awneil The filter(s) between tap-2 & valve-1 might cause a problem there...
valusoft Maybe a one way valve in parallel with the filter... thinking out aloud only.
I have plans to attach a 1.2 lts capacity of rubber box for holding a liter of water at the tank's outlet with valves both at the inlet and outlet of the box. Just exactly how much space would be required for air trapped inside to not be an issue?
I hope that would solve the trapped air issue as per discussion.
valusoft Prakash,
Sorry, I have no idea what you are proposing. Where are the valves? How are you measuring 1 litre?
The arrow marks are the pipelines in which a valve would be fitted. Inside the one liter box I would have water level indicator to measure the amount of water
valusoft Water level indicator... so you will be measuring with a human eye?
So the "valves" will just be taps...
No No Sorry for the confusion. The valves are real solenoid valves and the water level indicators are sensors.
valusoft OK, I'm out of here... merry-go-rounds make me dizzy.
awneil I hope that would solve the trapped air issue as per discussion.
Surely, the way to solve the trapped air issue is very simple: do not trap air!!
Why deliberately make problems for yourself?!
Prakash - may i ask how old are you? Knowing the audience means we can adjust our responses accordingly. I mentioned before that there are solutions all around you. Many were developed centuries ago. I'd suggest you acquaint yourself with the fundamentals. Humans have handled water since they first walked the earth.
Well I am an Engg student doing this project for a client Since I am learning the basics, this forum has been a great source of enriching my knowledge.
microcarl Well I am an Engg student doing this project for a client Since I am learning the basics, this forum has been a great source of enriching my knowledge.
Have you taken --- ANY --- basic physics in your engineering program yet?
Personally, I'm thinking a one liter bucket that can be manually dipped into the water storage tank by an actual human (or monkey) might be your client's best option. That, or simply use all the conveniences of modern technology and fill the one liter container via conventional water faucet (or tap).
I have often made the statement that "Misapplied technology is often times, worse than no technology at all !!!"
And then too, there was that arogant young buck who, about 30 years ago, purchased a book on computers and, before finishing that book, began marketing his (nonexistent) computer skills to the manufacturing industry where, he successfully gave every real computer consultant a bad reputation that still exists today.
OK, I'm out of here... merry-go-rounds make me dizzy.
You have more patience them I do.
I would help if I could figure out what the question was.
awneil I would help if I could figure out what the question was.
Indeed!
This whole multitude of threads is a prime example of why it's important to describe the goal - not (just) the step:
Engineering is about applying science to solve real world problems. I'd suggest the science here is high school thermodynamics.
If you remove fluid from a closed container, you'll create a vacuum. Eventually the force of the vacuum will overcome the force of gravity and no fluid will flow. How to solve? Put a hole in the closed container. Commonly called a 'vent'. How big a hole? That's when you apply the science. Suddenly all those 'useless' equations you've (hopefully) learnt start to make sense.
