Water Level Alarm

Rajkumar Sharma      http://www.rajkumarsharma.com  
Project tested



This project is a water level alarm.


Water Level Alarm is a simple project to detect and alarm once the water level in tank or Aquarium reaches at certain level. Circuit is based on popular NPN transistor BC547 which act as switch, Sensor also made on PCB, when the water reaches the sensor PCB, base of transistor connected to positive supply, in consequence transistor act as switch and activate the buzzer.


  • Input: 9 VDC @ 40 mA (Supply range 5V to 12V DC)
  • Works good with 9V PP3 Battery
  • Project has two PCB ( 1. Sensor 2. Buzzer driver)
  • Output: Buzzer
  • Buzzer Included
  • Terminal pins for supply voltage
  • Power-On LED indicator
  • Four mounting holes of 3.2 mm each
  • PCB dimensions 32 mm x 35 mm









9 Response on “Water Level Alarm

  1. Great little circuit! How to modify this design so that it will work off electric power (115vac) instead of battery power? Would appreciate your reply. Thanks!

  2. Use one door bell & place it near switch of water lifter pump, use two wires one at bottom of tank second at upper level of water, bell will ring when water comes up, use only battery (cell) any body can arrange it

  3. @Mohamed Said
    Instead of buzzer place resistor typically 100kOhm would do it (higher if that npn allows it.) then monitor with your arduino between the resistor and the npn transistor. If you see voltage there that means no current so buzzer is off. If you see a short there that means that there is current hence the buzzer would have been on. If you wish to leave the buzzer then the buzzer would act as a resistor. although i was under the assumption that piezo buzzers were ac not dc so not sure how this one buzzer works….

    1. This circuit has one sensor. So you may use two of these. one on the top and one on the bottom and you will have an indication when the tank is full or empty.

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