Transistor Based Water Level Alarm Circuit

Sometimes the water tank becomes full, but we forget to switch OFF the motor, as a result, the system wastes water; so, this simple Transistor Based Water Level Alarm Circuit is useful, as it gives sound alert when water reaches a level.

Moreover, the circuit is cheap and easy to build as it uses very few components and therefore, beginners can easily make this project.

Circuit Working:

Parts List:

Components	Values	Quantity
Resistors	47k, 1k	1 each
Capacitor	Electrolytic 100uF 25V	1
Semiconductors	BC547 NPN Transistor	1
	9V DC Buzzer	1
	5mm Red LED	1
	ON-OFF Switch/ Toggle switch	1
	9V Battery	1
	Water level probes like metal wire or copper strip	2

The above circuit is a simple water level alarm which uses one transistor, one buzzer and two probes.

First of all, switch S1 turned ON and battery provides 9V supply.

Here, water works as a conductor but initially there is no water between probes, so no current flows to transistor base and therefore, transistor Q1 remains OFF; hence, buzzer does not sound.

Now, when water rises it touches both the probes, because water conducts electricity and current flows and then base current flows through resistor R1 and as a result a Q1 transistor turns ON.

Now, collector current flows and so 9V buzzer gets power and then buzzer starts sounding loudly and at the same time the LED glows.

Thus, alarm indicates water level has reached and after that when water goes down the alarm stops.

Formula with Calculation:

The general calculation for base current, mentioned below:

Supply Voltage V = 9V

Base resistor R1 = 47k

Assume base emitter voltage Vbe = 0.7V

Base current Ib = (V – Vbe) / R1

Ib = (9 – 0.7) / 47000
Ib = 8.3 / 47000
Ib = 0.000176 A
Ib = 0.176 mA

Hence, this base current is enough to turn ON BC547 transistor.

How to Build:

To build a Transistor Based Water Level Alarm Circuit follow the below steps:

• First, start the circuit by collecting all the parts as shown in circuit diagram.
• Then, transistor Q1 emitter pin connected directly to negative line of battery, base pin connected to one end of resistor R1 and other end of R1 goes to one water probe and collector pin connected to negative terminal of buzzer and capacitor C1.
• Then buzzer positive terminal goes to positive supply line.
• Now capacitor C1 100uF positive terminal goes to positive supply.
• Also, resistor R2 and LED connected in series from positive supply to GND.
• Further, water level probes one probe connects to base resistor R1 and other probe connects to positive supply line.
• After that, battery positive goes to switch S1 and switch output goes to circuit positive line and battery negative goes to circuit ground.

Conclusion:

Overall, this simple Transistor Based Water Level Alarm Circuit is very useful for our home, farm and office and it helps prevent water overflow and also it saves water and electricity.

Moreover, it is easy to build at home and even beginners can try this project and therefore, this circuit is best for basic electronics learning.