I will Teach you how to make a simple water sensor circuit

Step 1: 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

Read Circuit Diagram

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

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

Here are some mock ups of how to connect it to a HHO Cell or just detect water.


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
<p>how do you prevent corrosion on the wires? I want to use it in the ocean and corrosion will be a problem.</p>
<p>Even I have similar plan and did some reading about &quot;Electrolytic corrosion&quot; and found out that inert metals like platinum or gold dose not corrode. but they are a bit expensive for me :) So I am planning to use a good stainless steel rod's as probs as they corrode and eaten away very slowly compared to copper and aluminium. I think graphite (pencil lead) also makes good electrode.</p>
an option would be to use gold electrodes
<p>If you're doing this for drinking water DON'T USE STAINLESS STEEL !!!</p><p>I was going down that path too, thinking that there will be little/no corrosion, but then I noticed a strange substance in the water. Turns out that using stainless steel as electrodes is a bad idea as it releases a poisonous substance! ...</p><p>See http://antique-engines.com/stainless-steel-electrodes.htm</p>
<p>look for stainless steel wire used for welding and use terminal board for conexion</p>
<p>Can you show me the diagram in PCB ?</p>
Hi we are planning to use this circuit in our project but how do we calibrate it?<br>Thanks
adjust the variable resistor to calibrate
<p>Thanks for the tutorial. I's helping me make automatic watering bowls for the dog and cats. </p><p>I got it working with the LED, but I can't get the arduino to read the on/off. I tried connecting wires where the LED should be to a digital pin with DigitalRead, and an analog pin with AnalogRead, but can't read any sort of signal. </p><p>Any ideas on how to interface this with an arduino?</p>
try connecting 220 ohm resistor between emitter and ground and connect arduino pin between emitter and resistor then see if you can sense any voltage
<p>Thanks for the reply. For anyone else wanting to detect water with arduino - turns out that you just need to connect a 10k resister between 5v and A0, then connect the probes to A0 and GND. Works like a charm :)</p><p>Great circuit/tutorial though, I'm sure I'll find a use for it outside of my aurduino project</p>
<p>Thanks for the reply. For anyone else wanting to detect water with arduino - turns out that you just need to connect a 10k resister between 5v and A0, then connect the probes to A0 and GND. Works like a charm :)</p><p>Great circuit/tutorial though, I'm sure I'll find a use for it outside of my aurduino project</p>
<p>I put a dpdt 12vdc relay in place of the LED. Now I can control the water level on my model steam boiler.</p><p>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.</p><p>FYI: Don't use an autmotive battery charger as a steady power supply.</p>
<p>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</p>
<p>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.</p>
<p>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.</p>
<p>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.</p>
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&quot; 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.
<p>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 </p>
<p>Hi, did you post the circuit as described above (ie to prevent on/off/on) using 555 timer etc?</p>
<p>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.</p>
<p>Is this working?</p>
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? <br> <br>Regards!!!
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<br> 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.<br> 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 :<br> <br> G:)
how it works <br>
I like that you put the 22k resistor in &quot;Step 6&quot;, and this can be used in the circuit in &quot;step 2&quot; 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 <br> <br>Also with a 12 volt supply, you'll want use a higher value resistor than 330 ohms on the LED. <br> <br>The circuit will probably work without the potentiometer. <br> <br>
how much cost of this project in india<br>
please give me a detailed process of fuctioning of a transisitor in a water level indicator project.<br>
is any other option not available,i m really not getting it.........
here transistor is used for amplification ??????<br>and why only BC547 OR 548 is used???
I know I have bad hand writing but it also says any NPN transistor will work
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. <br>
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?
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 ???
do you have the c-language for this project
are you done with this thing??
can nybody eloborate on which HHO cell to use!!!
I would recommend a dry cell the circuit would be placed on the water fill tank
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
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
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?

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