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Picture of Simple Water Sensor
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12v water sensor.bmp
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I will Teach you how to make a simple water sensor circuit

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
 
vederstein made it!1 month ago

I put a dpdt 12vdc relay in place of the LED. Now I can control the water level on my model steam boiler.

It was a pain though. The documentation I had on the transisistor had me wire it backwards. Also, the power supply I was using was way too noisy. After taking the battery out of my classic car, it worked.

FYI: Don't use an autmotive battery charger as a steady power supply.

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vederstein1 month ago
Miken83 months ago

Just wondering how I could make a very simple sensor to detect when something is no longer in water. So when the water sensor is no longer active it will alarm with a small speaker/beeper. I want to make something to put in a float used for crab pots so if a would be thief attempts to remove it the speaker is activated. Hopefully something low voltage. This would be in salt water if that makes any difference

TomHoag6 months ago

It is simple and very effective! Note that the circuit response will vary depending on the medium such as fresh water, lake water, salt water, etc.

Wayne TheS10 months ago

Thanks....the video saved me from pulling my hair out. Was not aware in re: tying the pot half to ground. I intend to use this as an auto switch on my bilge pump. I intend to add a three way switch, Off, Auto, Manual. I assume I will need to amp up the output to pull in a micro relay? If I am not mistaken the relay will require about 60 ua ....have not gotten it in yet to see. Any suggestions? Thanks for a great vid.

Cyberscann54 (author)  Wayne TheS10 months ago

I could see replacing the LED with a relay most relays are designed to operate from low voltage sources and switch on or off a high voltage supply so just remove the LED and its resistor and put a relay in there place and I'm guessing this is for a boat so powering it should be easy with no changes to the circuit since boats use a 12v system the circuit was designed for 12v you just need a 12v relay that can handle the pump. Thank you for the comments and good luck.

Thanks for the info...For anyone else interested, I will also be including a delay off timer of 10 secs or so in order for the water level to fall well below the probes and prevent an On/Off/On/Off scenario from wave action etc. The probes will be mounted about a 1/4" above the highest point of intake of the pump...this should allow the pump time to lower the level to the point of cavitation and then shut off....leaving the probes well out of the water.
Cyberscann54 (author)  Wayne TheS10 months ago

well since you want a delay timer a 555 or 556 chip can be used and the sensor can also be built from it if you want I can design the circuit for you and all you will need to do is get the parts and build it just let me know if you want me to do it

Hi, did you post the circuit as described above (ie to prevent on/off/on) using 555 timer etc?

That would be great! Keep in mind that I am new to electronics (66 yrs old) so I do well with pictures :) I have plenty of 555 and 556's as well as ATTiny 13 and 85's as well. I have managed to struggle through burning the Tiny's with an Arduino ISP. I am thinking a delay off of about 45 sec, with the probes about 1/4 above the intake should give the pump enough time to drop the level well below the probes. Thanks for any help. BTW...the detector circuit works flawlessly but I would never have figured it out without your vid...which was outstanding.

RanzelM9 months ago

Is this working?

rpérez231 year 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?

Regards!!!
nervrunna2 years 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 :

G:)
EUROGUAGE ELT4 MK2.jpgEGeltmk4_a.jpgEGeltmk4_b.jpgEGeltmk4_c.jpg
paxipatel3 years ago
how it works
mr_man3 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.

sala893 years ago
how much cost of this project in india
manjotmessi3 years ago
please give me a detailed process of fuctioning of a transisitor in a water level indicator project.
mboruah3 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
jpsailr5 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_tako4 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)  wonderingoutloud4 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 ???
palabuto5 years ago
do you have the c-language for this project
Zhelnot5 years ago
are you done with this thing??
geniusgippy5 years ago
can nybody eloborate on which HHO cell to use!!!
Cyberscann54 (author)  geniusgippy5 years ago
I would recommend a dry cell the circuit would be placed on the water fill tank
mathew0866 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
DarkAngel096 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 version..it is more complicated but the results far better for me so far at 1Ltr/Min @12v/5A
vancecook77 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?