12v water sensor.bmp
water sensor.JPG
I will Teach you how to make a simple water sensor circuit
Remove these adsRemove these ads by Signing Up

Step 1: Gather Parts

Picture of Gather Parts
Parts List
1 General Purpose NPN Transistor $0.10
1 50K Trimpot $0.15
1 47ohm Resistor $0.01
1 LED $0.08
1 Proto Board or You can etch A PCB
1 3 volt power source battery, wall wart, whatever

Step 2: Learn the Layout

Picture of Learn the Layout
12v water sensor.bmp

Read Circuit Diagram

Step 3: Create PCB (skip step if using Proto board)

Picture of Create PCB (skip step if using Proto board)
12v water sensor.PNG
The Schematic is made with ExpressPCB which is a free PCB Layout Software you can download it here
Than Download the PCB file and open and print it and make your PCB. Here are a few links to Instructibles that show you how to make a PCB
water sensor.pcb is 3v
water sensor2.pcb is 12v
Cheap and Easy Toner Transfer for PCB Making
The Saltwater etch process

Step 4: Build It

Build time will update once I make the PCB

Step 5: Connect to HHO Cell or Any other Water Sening Probe

Picture of Connect to HHO Cell or Any other Water Sening Probe
Here are some mock ups of how to connect it to a HHO Cell or just detect water.


Picture of 12 VOLT CIRCUIT
12v water sensor.PNG
Here is how to setup the circuit to run on 12 volts from a car battery the circuit is still the same just some resistors are added to the probes to protect the transistor and a larger resistor to protect the LED
rpérez238 months ago
I loved this, I built it and works nice with any NPN transistor! There is other question, how do I make it work the other way? to turn on the led when there is no water and turn off when water get the sensor? My friend briefle told me is siwtching the Variable resistor with the sensor, but I tried and It did not work, I am not sure if that would be. How cold you do it? like a Dry detector?

nervrunna1 year ago
Nice! below is a reverse engineered water sensor circuit. Its ancient, but it still works like a dream. Its an AC circuit, so it wont eat the electrodes and it
It takes two sensor inputs: One for sensing low tank level and the other for sensing a full tank level. It basically boils down to the ability to have for example an automatic fill system. So when the level gets to the bottom sensor, the pump comes on and fills it until it gets to the top sensor.
I drew the schematic directly from the board. It has old components and some of them Im not sure what their values are. If anyone could elucidate, it would be nice :

EUROGUAGE ELT4 MK2.jpgEGeltmk4_a.jpgEGeltmk4_b.jpgEGeltmk4_c.jpg
paxipatel2 years ago
how it works
mr_man2 years ago
I like that you put the 22k resistor in "Step 6", and this can be used in the circuit in "step 2" as well. It reduces the probe current, and protects the transistor in the event that the probe electrodes touch each other and short, and reduces the chance of electrolysis generating gas bubbles on the probe electrodes. Also to reduce electrolysis, you could just use 1.5 volts across the probes

Also with a 12 volt supply, you'll want use a higher value resistor than 330 ohms on the LED.

The circuit will probably work without the potentiometer.

sala892 years ago
how much cost of this project in india
manjotmessi2 years ago
please give me a detailed process of fuctioning of a transisitor in a water level indicator project.
mboruah2 years ago
is any other option not available,i m really not getting it.........
here transistor is used for amplification ??????
and why only BC547 OR 548 is used???
Cyberscann54 (author)  sahilaggarwal3 years ago
I know I have bad hand writing but it also says any NPN transistor will work
jpsailr4 years ago
After many attempts to make a circuit like this, I gave up. Reason: when current flows through water from one plate to another, gas builds up on the sensor plates and the conductivity of the water reduces until it is undetectable, over 10 megohms within minutes. So if you're not there right when it happens, you will miss it. I solved this by creating a circuit which would put an AC current on the sensor plates. This continually purges the plates of gas and keeps the resistance through the water to less than 100 Kohms - very useable. This test ran for over 4 hours with no loss of conductivity. Now I successfully use it to detect bilge water as soon as it happens, or water on the basement floor. I will submit a project when I get it written up.
I am working on a hybrid hot water system and need something like what you are describing... can you please forward me some more information on it please!! Thank you.
eng_tako3 years ago
thank you very much you help me alot
Assuming clean water, zero turbulence, very small inflow related to volume, could I get 1/32 inch level gage accuracy? In other words, under perfect conditions, what accuracy could one expect?
Cyberscann54 (author)  wonderingoutloud3 years ago
it is a circuit designed to give you a visual alert that you need to fill you water tank in a vehicle accuracy is not part of its implementation being cheep and simple is. If you wish to have a sensor circuit that is that accurate this is not the way to go. Why do you need such accuracy what are you trying to build ???
palabuto4 years ago
do you have the c-language for this project
Zhelnot4 years ago
are you done with this thing??
geniusgippy4 years ago
can nybody eloborate on which HHO cell to use!!!
Cyberscann54 (author)  geniusgippy4 years ago
I would recommend a dry cell the circuit would be placed on the water fill tank
mathew0865 years ago
Hey... I find this one soo interesting n simple that i am planning to try oit put once. but i have a small question? How much current does the circuit consume for one time function. meaning if the circuit detects water how much currents is consumed by the circuit from the 12 V battery??? thanksss
That's pretty easy to figure out with Ohm's Law. There are two paths that current will take through the circuit: the first is through the LED and into the collector of the transistor, and the second is through the probes, the water itself, and the 22K resistor. The current through the LED part of the circuit will be about 36mA, and assuming the water has perfect conductivity (it definitely doesn't, but that's a worst-case scenario) the current through the probes will be under 1mA. In other words, trivial.
oo very cool and underated
DarkAngel095 years ago
Seems like a really cool project I may have to try it out. We have a sensor project in school to do I may use this project for it. Ill send you the results if you are interested.
PS electrolyte is a good move too...baking soda is a good start.....
I have built some equivalents to this and the results are OK but not great...look up the dry cell is more complicated but the results far better for me so far at 1Ltr/Min @12v/5A
vancecook76 years ago
If anyone has built and tested this in an actual cell, please let post the results here. I am curious if foam may conduct enough to keep the LED from lighting when the water level drops but cell is still in operation. If the cell is in a vehicle, do corners trigger the circuit?