Water level indicator using seven segment display

[shariq92]

Hello Everyone.
I am making a little hobby project.
The project is simply to represent the water level in a tank.The main idea is to construct the project using logic gates, decoders or encoders.

My approach to the problem is taking the logic level (111111111) and converting it to bcd(8421) code and then using a bcd to seven segment display and finally the seven segment display itself to display "9".
I have made the (111111111) to bcd code part. But i am confused about how i should go about taking inputs. One approach is to use a transistor as a switch to turn on the path from Vcc to the encoder.
Any other idea??
Also is the approach in general correct??

 

[pairofstrings]

I think using only transistor will only give you idea only if the tank is empty or when it is full. What if you want to know actual level of water in the tank at any random time?

 

[Bob S]

Do you want a single digit readout, "0" thru "9"? The hardest part of this project, which you are avoiding, is the selecting and designing the transducer for determining the water level. Can you make electrical contact with the water? Several ways might be 1) an oscillator whose frequency is dependent on water level, 2) a pressure transducer at bottom of tank, 3) a string of high-meg resistors in series, 4) sonic echos, or 5) a float with encoder. There are probably other solutions too. Google "water depth measuring devices" for ideas. For some, you will need an ADC or a string of comparators to convert analog to digital.

You are an electrical engineer (I assume), so calculate the capacitance of a length L of two concentric cylinders (copper tubes), diameters D₁ and D₂. Calculate the capacitance. Now put in water, with a dielectric constant of about 80. Can you design an oscillator that is dependent on this change of this capacitance? Is the change of capacitance, or frequency of oscillator (NE555?), linear in the depth of water?

Bob S

 

[shariq92]

Simply put i intend to take inputs by connecting the collector of a transistor with a Vcc and the emitter becomes the input for the system. By placing the base terminal and Vcc in water i will use the transistor as a switch.
My intention is to get water level at 9 different levels. If the water is in between two levels than i am shown the value of the lower level on the seven segment.

 

[shariq92]

@ BOB S
I am doing this for my home tank.
We have a tank on the roof that is filled by a motor. I just need to know how much water is there approximately so i can decide when to turn on the motor and when to turn it off. But i thought it would be good to know how much water has filled so i am making nine different levels.