# water controller

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#### Jlkdvf

##### New Member
hi,
i've just registered here.. i'm a student,
i would like to ask for your help for our project that is very new for me...i would like to ask if you have a circuit diagram for controlling the quantitiy of water when it goes out from the system.. for example i press 500 ml then exactly 500ml will come out..

thanks =)

##### New Member
If you're planning on 'pressing 500ml', what sort of hardware is going to be used? Will this be on a keypad or something of that nature? How will the water be stored, how will it be released? If this is a 'homework assignment', what types of hardware / electronics components are available to you?

I would think the simplest solution would be to arrange the hardware so that the rate at which water can leave is a constant, and control the time for which the system is 'open' and can pass the water using a timer; though you'd need a fast way of fully opening the nozzle / unblocking the hole, or whatever will allow the water to pass, so that you don't have varying flow rates as the state is being changed.

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#### Jlkdvf

##### New Member
it is for innovation..
our plan is to make a water filter at the same time quantity controller and if also we can with water cooler and heater.. my problem is that i can't find any schematic diagram for this.. thanks for your response.. =)

#### ericgibbs

##### Well-Known Member
it is for innovation..
our plan is to make a water filter at the same time quantity controller and if also we can with water cooler and heater.. my problem is that i can't find any schematic diagram for this.. thanks for your response.. =)
Fill an intermediate water cystern with 500ml of water and dump that into the output.

#### Boncuk

##### New Member
There are liquid flow sensors on the market working very precisely regardless of the liquid pressure. They are widely used to fill bottles at breweries.

##### New Member
There are liquid flow sensors on the market working very precisely regardless of the liquid pressure. They are widely used to fill bottles at breweries.

Probably the best idea. There are many factors which could affect flow-rate, so time 'on' may not be a reliable means of setting the volume passed; ericgibbs' idea of using an intermediate cistern doesn't really change anything since it would still need to be able to control the volume of water being passed into this cistern; seems like an unnecessary addition.

#### 3v0

##### Coop Build Coordinator
Forum Supporter
The people who mix chemicals for agricultural chemical application have this problem. There are two solutions. One is flow sensors. The other is to do as ericgibbs suggested and have the chemical flow into a measuring device, or exact size container first.

I think (would like to know if I am wrong) that you will find flow sensors to be expensive. But I would guess that depends on your budget.

3v0

#### Boncuk

##### New Member
I just recall flow meters used in cars for trip computers. They had a small turbine and the output was frequency.

Don't know if they are still on the market. They were about US$15. Here is a datasheet of the cheapest on the market (US$355). Brand name is "Blancett".

To Giftiger Wunsch: It makes sense filling a cysterne as an intermediate step using a strain gauge to measure the amount of liquid. Strain gauges are much cheaper than flow meters and reliable and accurate, too.

That way the system can be held at moderate cost not having to bother with changing pressure.

Boncuk

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#### Boncuk

##### New Member
yet another one

Conrad electronic offers a cheap flow meter (€20.96 = US\$28.30).

Attached is the datasheet with different interfacing methods.

Boncuk

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##### New Member
To Giftiger Wunsch: It makes sense filling a cysterne as an intermediate step using a strain gauge to measure the amount of liquid. Strain gauges are much cheaper than flow meters and reliable and accurate, too.

That way the system can be held at moderate cost not having to bother with changing pressure.

Boncuk
I apologise if my statement was misleading then; it just seemed poorly explained as he seemed to be suggesting adding a cistern with a preset volume limit, which wouldn't be appropriate if they wanted to be able to adjust it to almost any value using a keypad.

If flow sensors are over-budget, how about using mass? I'm sure others would know better than I do, are there any components which could use the change in mass of the cistern to determine the volume of water and thus adjust the position of the valve? Water has a more or less definite density of 1g/cm³, of course this varies with temperature, etc., but the effect should be minimal.

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