The final circuit diagram and design can be seen above. We also thanks to our sponsor JLCPCB( for sponsoring us PCB for this project.


Thanks To JLCPCB. $2 for 1-4 Layer PCBs.

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Component List  -

  • PCB
  • LED – 5mm
  • Resistor – 1 KΩ
  • Buzzer
  • Transistor – BC 547
  • Power Source – DC 12v
  • Soldering Iron
  • Cutting Plus
  • Water

Water Level Indicator Circuit Design

The schematic of water level indicator circuit along with the PCB layout can be seen above. Here LED and buzzer used to watch and hear the signal of water level. Power supply don’t included with the circuit. You can use any DC 12v adapter or 12v battery.

Transistor Pin Out

We know that, there are two type of transistor. Every transistor contain 3 legs and this 3 legs have different names. Here BC547 is an NPN transistor and if we count it’s leg from left side, then 1st leg “Collector” 2nd leg “Collector” and 3rd leg “Emitter”

Connect LED Lights

To make this water level indicator we are using 5mm LED lights. Here 5 led should be 5 different color. We connect all LED positive leg with DC 12v positive cable and connect LED negative cable with resistors.

Connect Resistors

We are using 1 KΩ resistor to make this circuit. We connect resistor one terminal with “Collector” leg of transistor and resistor other terminal with negative leg of LED lights.

Connect Buzzer

For alert signal, we are using a buzzer. When the water tank will full, then the buzzer will make sound and let you know that the tank is almost full with water. We connect buzzer positive leg with LED positive leg and buzzer negative leg with resistor.

Connect Transistors

Now we connect transistor with the circuit. We connect 5 piece BC547 transistor with the circuit. We connect all transistor “Emitter” leg with negative leg of DC 12v power supply.

Our circuit is now ready for use.

Soldering And Cleaning

Neat and perfect soldering is an important part of all kind of PCBs. Since soldering, you should remember that, there should not be any kind of short circuit. After soldering all leg, we cut-off the extra leg of all electronics component.

Final Action

Our circuit, is now completely ready for use. Now we just connect power supply with the circuit.

Put every transistor “Base” leg inside water tank and check the circuit. Again thanks to JLCPCB for best quality PCBs.