water level indicator circuit design

[siddharthtaunk]

Hello All,

I have some questions regarding water level indicator desing

(w.r.t the schema attach)
1. Why only 6V AC is ude for detection. why not 5, 4 or 7V
2. How can a AC source drive a transistor in active region.

Thanks in advance.

SID

 

[ALERTLINKS]

1. Why only 6V AC is ude for detection. why not 5, 4 or 7V

It is not to be precise. You can use 5, 4 or 7V. Adjust value of resistors to limit current to LEDs.

2. How can a AC source drive a transistor in active region.

Most probably its a typing mistake. Consider it as "6V DC".

 

[FvM]

It's a badly designed circuit.

Usually level indicators are using AC voltage to avoid electrolysis and respective electrode corrosion.

But the transistor switches and LEDs don't actually work for AC. The base-emitter diodes and LEDs will still rectify the AC voltage, causing a DC current and electrolysis. At higher AC voltage, transistors and LEDs that aren't designed for reverse voltage operation and might be damaged. The circuit could be supplied with DC voltage as well.

Most probably its a typing mistake. Consider it as "6V DC".

Sounds plausible. The electrolysis problem holds, however.

 

[siddharthtaunk]

It's a badly designed circuit.

Usually level indicators are using AC voltage to avoid electrolysis and respective electrode corrosion.

But the transistor switches and LEDs don't actually work for AC. The base-emitter diodes and LEDs will still rectify the AC voltage, causing a DC current and electrolysis. At higher AC voltage, transistors and LEDs that aren't designed for reverse voltage operation and might be damaged. The circuit could be supplied with DC voltage as well.


Sounds plausible. The electrolysis problem holds, however.

Thanks for the reply.

So do u mean to say that I have to convert the AC back to DC to have the circuit working properly?

and can you please answer the first question. why do we need to use 6V AC only why not 5,4 or 7? I have read that "choose the supply voltage based on the electrical conductivity of the liquid" in this case its water. What is the formula to calculate it.

Thanking you in anticipation.

Siddharth

 

[siddharthtaunk]

Thanks for the reply.

So do u mean to say that I have to convert the AC back to DC to have the circuit working properly?

and can you please answer the first question. why do we need to use 6V AC only why not 5,4 or 7? I have read that "choose the supply voltage based on the electrical conductivity of the liquid" in this case its water. What is the formula to calculate it.

Thanking you in anticipation.

Siddharth

can no one answer this question
Why a water level indicator shown above requires 6V why not 5V or 7V
I just know its regarding the conductivity of the liquid
But how please help

 

[jayanth.devarayanadurga]

You can use 5V DC but put the LED between resistor and collector.

 

[thannara123]

This type of desgin may loss some power ...

 

[goldsmith]

Why a water level indicator shown above requires 6V why not 5V or 7V

Hi
If you read post of "FvM" precisely you'll get that the circuit is not good . so why you're going to focus on a circuit which is unreasonable ? i believe time has more worth . isn't it ? if you want i can guide you to design a much better circuit for water level indicating .

But if the question is important for you i can answer it however i prefer i'd rather to don't .
If you understand load line of those transistor each one independently you'll catch why it requires 6 volt . are you familiar with DC and AC load line and quiescent point of a transistor ?

This type of desgin may loss some power ...

Loss some power ? is that important here ? you think that some mili watt is important ?

Best Wishes
Goldsmith

 

[thannara123]

Hi


Loss some power ? is that important here ? you think that some mili watt is important ?



Goldsmith

Most of the time the Tank has full water ....
so the 5 transistor, most time is in ON mode .
Sir ,thats why I think it is not better circuits .

 

[goldsmith]

Most of the time the Tank has full water ....
so the 5 transistor, most time is in ON mode .
Sir ,thats why I think it is not better circuits .

Calculate the power consumption ! Ploss of transiostors = VCE*ic and the transistor works in on/ off state where in on state voltage is nearby zero ( approx ) and in off state current is nearby zero so the loss power is insignificant .
power consumption of LEDS are so low too . and dissipation across each resistor is pretty low too . so it still doesn't make any sense that we think about dissipation in this case .
Best Wishes
Goldsmith

 

[thannara123]

Thanks agreed,
But Only this type of desgin are there ?

 

[goldsmith]

But Only this type of desgin are there ?

This type of design are what ? what you mean by that ?

 

[thannara123]

Means, here testing each transistor's base voltage ?(at different level )
Design means , any other type of water level indicator . (using other transducer ).
I am sorry ,am feeling to deviate the actual threads content ...:-?

 

[goldsmith]

Means, here testing each transistor's base voltage ?(at different level )

You're confusing me . what you mean by that ? do you mean how to measure it ? or how it works ? i can't catch your right meaning . so describe it accurately please .

Design means , any other type of water level indicator . (using other transducer ).

it can be easily done by some op amps or just one op amp in linear mode . or some transistors or just one transistor with some leds with different colors . or ... there are to many ways for a water level indicator .

 

[thannara123]

Sorry for my bad English ..
i asked you to that is there any other type of desgin other than the using multi leads for detecting the water ?
means something new ?
is there any desgin to detect the whole level by a single lead (electrode ) ?

 

[goldsmith]

Sorry for my bad English ..

Don't worry about it , english is not my native language too :wink:

i asked you to that is there any other type of desgin other than the using multi leads for detecting the water ?
means something new ?
is there any desgin to detect the whole level by a single lead (electrode ) ?

One LED ? it is impossible unless with changing the glow of the LED which is not precise . another way is using an LCD to write level of water .

 

[thannara123]

Sir I meant not an LED its i meant lead .
For example :- I have an idea using a 2 lead of electrode which is dipped in water to sense the level by detecting the current .
is there a different current with different water levels ? And can we calculate the current levels as water levels ?

 

[liteon]

The circuit in the first post if worked properly will have its own draw backs,until it is being adopted for study or practice.
The sense leads having certain voltage levels when dipped in water will start oxidizing rapidly and minerals in the water would start to build up around them and soon they will fail to detect the level and cleaning them may not be easy job.
If you Google it you will find better solutions and micro controller based designs using a variety of sensors ranging from simple floating switches to pressure sensors.

 

[goldsmith]

Sir I meant not an LED its i meant lead .
For example :- I have an idea using a 2 lead of electrode which is dipped in water to sense the level by detecting the current .
is there a different current with different water levels ? And can we calculate the current levels as water levels ?

Then sorry for my misunderstanding at that time . ( it was morning and i was awaken since it's last night ! )

The idea of measuring the current by two electrodes is popular and it is used and it will work as well .
Best Luck
Goldsmith

 

[FvM]

Sir I meant not an LED its i meant lead .
For example :- I have an idea using a 2 lead of electrode which is dipped in water to sense the level by detecting the current .
is there a different current with different water levels ? And can we calculate the current levels as water levels ?

A conductive continuous level measurement has the drawback of depending on water conductivity which might vary over several orders of magnitude. A more accurate method (used in some commercial sensors) is a capacitance measurement using an isolation coated electrode.

As already mentioned, a conductivity measurement must use AC voltage for long term stability.