Water Level indicator using Transistors

water level indicator using transistors

A water level indicator using transistors is a simple electronic circuit that is used to monitor and display the water level in a container or water tank. It uses a few transistors, resistors, and LEDs to to show the level of water in the water tank. This simple circuit is very helpful for the students of electronics to understand the working of electronics. This circuit is not durable but it can be used for short time.

water level indicator using transistors complete circuit

Visual diagram of water level indicator is given below.

water level indicator using transistors

Components Needed:

To develop the simple water level indicator using transistor we need the following components.

  • NPN Transistors (such as BC547 or 2N3904) – 4
  • Resistors 220-ohm- 3
  • LEDs (different colors are better for perfect indication
  • Sensors or ProbesĀ  (usually made of wires or metal rods)
  • 9v battery or Power supply
  • Buzzer

Water Level Indicator using transistor circuit diagram

Simple circuit diagram for 4 transistors circuit diagram of water level indicator is given below you can modify this circuit according to your requirements:

water level indicator using transistors

Working of Water level indicator

  1. Sensors/Probes: The probes or sensors are placed at different location in the water tank tank to sense the level of water. When water touches these probes or sensors, the base of transistors trigger the transistors and complete an electrical circuit.
  2. NPN Transistors: Each NPN transistor (Q1, Q2, Q3 and Q4) acts as a switch. When the base of the transistor is connected to a low voltage (because of water touch), the transistor turns on andĀ  current flows from the collector to the emitter.
  3. Resistors (R1, R2, R3): The resistors are connected in series with the transistors only to safe the LEDs connected for access current. You should use appropriate resistor values according to your supply.
  4. Diodes LEDs (LED1, LED2, LED3): The LEDs are connected to the collectors of the transistors. When a transistor is turned on due to water touching the corresponding probe, the LED connected to that transistor will light up, indicating the water level.
  5. Buzzer. With the last transistor a buzzer is connected. As you see in the circuit diagram there is no resistor with the buzzer because buzzer is 9v buzzer.
  6. Power Supply: Connect a power supply of 9-12V to the circuit.

As water level rises and touch to the sensor or probes the transistor turned on and corresponding LED turned on. In this way LED1, LED2 and LED3 glows and finnaly buzzer turned on. That indicates your water tank is full.

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