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