please i have a problem on this diagram when i connect it with 5v the arduino has a short voltage of current to supply it and the arduino will loss some voltage or it will turn off. do i need another supply for this diagram like 9v? i have connect also an LED its for water level indicator..i have attach the picture please advice me thankyou
You don't need 9V for this.
You can do with much higher resistor values for R4, R5 and R6.
I don't see the purpose of R1, R2 and R3. It may be useful to place resistors (10k or so) between the base of the transistor and the probe contact.
Another thing, assuming the probes are regular wires that are placed in the water, is that you will get electrolyses and very fast corrosion of those contacts, adding lots of copper to the water.
thankyou so i just put a higher resistor thankyou..and by the way whats the best wire for connecting to water ? it is solid or stranded wire ?
There is no wire suitable for connecting to water. Water and electricity is a bad combination, no matter how small the currents. Even at very high resistor values you will have these problems. Galvanic insulation is the way to go.
The way to stop electrolysis is by using high frequency AC (> 1 kHz), the way to stop corrosion is using non-corrosive probes such as gold plated connectors.
On top of this all you may get problems with ground loops.
Get a proper water level probe. Pressure, ultrasound or capacitive probes all keep the electricity away from the water.
oops im not using any sensor just wire that if the 5v is toogle
i have no sensors or ultrasonic to use..advice please
Do a search on this forum for water level detectors. You'll find lots of info.
please help or advice me for detecting the water without using any sensors any advice
Hi,
I have used this to some success
http://diyelectronicsprojects.blogspot.com.au/2012/08/fluid-level-sensor-circuit-diagram.html
N1 is an oscillator that via C1 applies AC signal to the water.
Just repeated the N2 circuit for as many water levels I needed.
Using N3 and N4.
Use the N2 output directly to your Arduino digital input, leave out T1 and the relay.
Tom... 
What sensors did u use?
Hi,
Just wires of different length, like you your original post.
Do you need a circuit diagram?
Tom..
i used that ..but is there a problem..i apply LED each transistor.. it so hard to detect water..
Hi,
Where did you apply the LED?
Did you use a current limit resistor?
How far between the UNO and the tank?
Tom..
Hi,
OP has continued over here.
http://forum.arduino.cc/index.php?topic=525726.msg3585859#msg3585859
Tom..
You can stick wires in water and sense the completed circuit using one microamp of current because that is all that an AVR input draws for one read. It is steady current that will eat your hardware quickest.
If you do one read per second or many seconds, you won't get much corrosion unless you leave it for a long time.
If the metals in the water are all the same then that will help. Stainless steel is one of the best choices there.
Put a magnet in something to make it float. Use a Hall switch to know when the water level raises.
You can stick wires in water and sense the completed circuit using one microamp of current because that is all that an AVR input draws for one read.
Several years ago I made a leak detector that I ran next to the washing machine.
Basically it was a 1 Meg pullup on an analog input. A twisted pair of wires ran from the input and ground to the location very close to the floor. At the end of the twisted pair wire I soldered a 0.1 uF 400V disc ceramic capacitor. The capacitor was physically large enough that I could hold it in a vise and break about 1/4 of it off, opposite to the leads. This exposed two close-spaced conductors with a "ceramic insulator and filter capacitor".
This was reliable for a few years. Once I did have to clean some lint and dirt off. It was located about 1mm ?from the concrete floor. I tested it with a cup of water spilled along the floor. I had to dry it all with a paper towel before it stopped alarming.
Hmmm. I REALLY should add one of those to my current Mega-based Home Automation. The washer already would have tested it and maybe avoided testing my mopping skills.
Why not continuing your previous thread?
i apply it in the 5v where you connect it
can connect all 5v in series?
i just made a prototype and i try it without any sensors like ultrasonic and i connect the 5v to the water immediate and another to the base of the npn transistor..