Water tank fluid control and LED alarm system. Basic

[Ch3ls3aFC]

Hello,

I am trying to make VI for a tank that has two valves. One is input valve and the other is output. When the input valve is open then the liquid is suppose to go up by 1 unit for every unit of time. and when output valve is open then the liquid is suppose to go down by -0.7 unit per unit of time. A green LED should be on when liquid is 0<L<20, yellow light when 20<L<25, Red light when 25<L<30. Now, if you look at my diagram, i think i am on the right track but the thing is that when both the valves are open then the differential is only 0.3 but it is suppose to increment, instead of incrementing the value of the tank stay 0.3 
Second problem is that when i close a valve then my add symbols keep waiting for a value from the valve that is turned off. I can't find a way to get a zero into that node using some kind of comparison or some other boolean function. 

I am new to Labview and i am really trying, i want to learn and not just ask for help but i am stuck really bad. i don't understand what approach to take.

Any help will be appreciated. 
Thanks.

[apok]

i would use a shift reg. to hold your tank value and put it all in one while loop...

Spoiler

[apok · Accepted solution]

modified...

Spoiler

[Ch3ls3aFC]

wow,

That is overwhelming... Now, i can just go ahead and copy this but i really want to learn and become a good developer. Could you just give me a real short summary of your appraoch on this, while mentioning some of these symbols. Some of these i have never even seen.

I really appreciate you concern and help on this.
Thank you

[apok]

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@Ch3ls3aFC wrote:

wow,

That is overwhelming... Now, i can just go ahead and copy this but i really want to learn and become a good developer. Could you just give me a real short summary of your appraoch on this, while mentioning some of these symbols. Some of these i have never even seen.

I really appreciate you concern and help on this.
Thank you

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glad i can help...please mark as solution and kudos those who helped! we get stroked by them since it is voluntary.... this will come in time as you learn LV, please take the online tutorials and pay for a learning membership. once you do that...you will learn and familiarize yourself with the small details. get involved in this forum and read,read and search the forums for answers.