Electronic Water Dispenser

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I am need to design a water dispensor which can detect amount of water dispatch. Say 100ml to 1-10lts. Also this dispenser would be placed in heat and dusted area.

 

What sensor / mechanism we calculate the water dispensed and how we should place the AVR controller away from heat and dust under sunny dusty area?

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Flow sensors have been discussed many times on the board, search for "flow sensor"

One thread had this link to a low cost flow sensor for a hot tub or pool I think.  

Would that work?  
http://www.banggood.com/Hall-Water-Flow-Sensor-Flowmeter-Water-Control-1-30L-Or-Min-2_0MPa-p-80747.html

 

There are many to choose from, depending on price range.

 

 

JC

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So if the rate of flow varies, or rather volume of water gushing from flow sensors vary i.e sometimes rate is less sometimes rate is high / medium - can it still capture volume of water dispense correctly each time?

Last Edited: Fri. Sep 26, 2014 - 02:40 PM
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I have not used this sensor, but in general, as long as the flow rate does not exceed it's max limits, then yes it should measure correctly. 

Can you give more details of your project?   Is this for a commercial application, or a one off hobby project.

What will you do with the flow rate data?  Display it, bill for consumption, log usage for long term study......  ???

 

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Ok, so what's "Electronic water?"

274,207,281-1 The largest known Mersenne Prime

Measure twice, cry, go back to the hardware store

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Forget flow sensors, they only measure what is dispensed. Use a positive displacement pump and deliver known quantities of water without using a flow sensor.

 

A simple easy to maintain peristaltic pump with a shaft encoder contains everything You need.

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Well please take my requirement as like to measure how much volume of water is dischared altogether. If it reaches a limit, we need to stop dispensing.

 

So a system that has to work dispensing say exactly 5 lts on each request. So imagine hundreds of person standing to collect water - they would press only a button and 5 liters of water would be dispensed. So will  a positive displacement pump / AVR will be able to to do so much of workload. The interval in-between each person collecting water could be less than 30 seconds.

 

What would be the best way to implment this project.

 

 

 

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Your average petrol pump is a positive displacement pump. These don't seem to have a problem. As for the 'best' way - that is up to you to decide. Best can mean many things. How about the humble toilet cisten? It fills up to a given level then you press a button that releases the measured amount of water. Repeat ad infinitum. Scale the tank for 5 litres, job done. No electronics needed.

 

 

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We have thought of same but we need three valves - one to open supply of water from main source,  second at the 5 lts container to get it filled and third to dispense water. So its like first two valves need to be open when 5 lits container is empty then they should close now open the third one. But we also need to ensure that a container is placed under the discharged nozzle.

 

This can be achieved via a circuit only I believe - will just a water level detector circuit be able to do that - do we really need an AVR controller to design it.  Since my concept is just at design phase I trying to make sure such that later we do not have difficulties. For validating whether a container is placed under discharged nozzle what logic we can use without the aid of any controller.

Last Edited: Sat. Sep 27, 2014 - 03:35 AM
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Prakash,

 

I don't think you have understood Kartman's suggestion.

 

A toilet cistern has two valves; one (operated by a float) to allow the water coming into the container/tank until the float is pushed into the position that stops the water coming in; and the other valve (the discharge valve) for emptying the container/tank. It has a push button linkage which opens the discharge valve allowing the water to flow out of the tank. When the water is flowing out, the float falls and that opens the inlet valve which starts the tank to refill. And the cycle repeats.

 

Study this explanation.

 

https://www.youtube.com/watch?v=...

 

Cheers,

 

Ross

 

Ross McKenzie ValuSoft Melbourne Australia

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A simple solution is frequently the 'best'.

What defines a 'container'? Is it always the same? The problem has probably been solved before - many times. Thus, look around you. 

 

Your solution could range from something simple as a specially shaped receptacle that only accepts the correct container and has a mechanism that opens a valve to something like a computer vision system and a electronic weigh scale.

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Is storing and dispensing the only way? Other option can we exactly measure the quantity of water dispensed - a mechanism that can be repeated over and over again within few seconds?

 

Yes, but one issue in this mechanism is that when and when only the container is filled with water I should allow user to press button to release water - say the container is getting filled in mean time user presses button - then it would be difficult to dispense exact volume of water - later if we want to make it a varying quantity like - 1 lt, 2 lts .. it would require some changes in system also or change in overall design

 

I should say that if we can measure a unit dispense like 100ml of water then I could easily quantify for further quantities of dispensing water ..

 

So something like read the level of water in container 1,2,3,4,5 lts .. after indication of collection of 5 lts  stop the valve to collect water. Now wait for user to request (say via 1 lts, 2 lts, 3 lts, 4lts, 5lts buttons) and then dispense it exactly the amount requested. This way in future if there is a requirement comes for modification only change required could be configuration

 

 

Last Edited: Sat. Sep 27, 2014 - 10:48 AM
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prakash_prasad wrote:
measure how much volume of water is dischared altogether.

If a flow meter gives you the rate of flow; volume is then simply rate x time - isn't it?.

 

Have you actually looked at any flow meter data sheets? I would imagine that they actually give you an output equivalent to "x litres per pulse" - so you just count the number of pulses for your required volume...?

 

Quote:
exactly 5 lts

There is no such thing as "exactly" - you need to specify your tolerance on that!

 

Quote:
they would press only a button and 5 liters of water would be dispensed

Is it always 5 litres? Or multiples of 5 litres?

 

If so, the "toilet flush" approach sounds ideal - doesn't even need any electronics!

 

 

 

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"It is easy to walk on water and deliver on any specification when both are frozen."

 

Ross McKenzie ValuSoft Melbourne Australia

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Thanks I understand all and everyone's point - so either I have to make use of flow sensor / weight sensor /  water level indicator.

 

Well I have never used flow meters - but say in case speed of water flowing through it is changing high to low / low to high OR force of flow is changing - the "x litres per pulse" concept for flow sensor cannot be used.

 

Pumps on other hands will be switched ON/OFF very frequently - will probably be burn out soon.

 

Weight sensors can be a good option and using it with water level indicator can give accuracy to even discharge of 100 ml. The issue I see is installation if containers are not of equal weight and we would be dependent on makers of it. What I am trying to state that the system is not robust or rather prone to bugs.

 

Though I may be wrong but I am trying a nearest to best steps covering below scenarios:

 

1. Water should dispense only when user wants it

2. A specific measurement of water can always be dispensed - say multiplication of 1 lts

3. When the water is dispensed - only requested amount should be dispensed

4. User can only select dispense option when system is ready to dispense

 

This reply has been marked as the solution. 
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OK Prakash,

 

I picked a cheapish flow sensor at random. Its datasheet shown below indicates the number of pulses per volume of water passed through it.

 

So your system counts the number of pulses until the required volume has passed and then turns off the valve. It doesn't matter how fast or slow the water flows. Your 100mL would be approximately 25 pulses.

 

Does that meet your needs?

 

Cheers,

 

Ross

 

Ross McKenzie ValuSoft Melbourne Australia