Full & Low Water Tank Alarm Project Using BJT ⚡💧

Managing water levels in overhead and underground tanks is essential to avoid wastage, motor damage, and inconvenience. A Full and Low Water Tank Alarm using BJT transistors is a simple yet effective mini electronics project for students and beginners. This project not only teaches the basics of transistor switching circuits but also provides hands-on experience in designing a practical water level monitoring system. With the help of NPN transistors (BC547) and float switches, this circuit alerts users whenever the tank is full or running low on water. Perfect for electronics learners, this project builds foundational skills in circuit design, logic gates, and real-life applications. 🔋💡

Parts Required 🧰

Resistors

• R1, R2 → 1K Ω
• R6, R7 → 1K Ω
• R3, R4 → 10K Ω

Transistors

• Q1, Q2 → BC547 (NPN)

Indicators

• Buzzer → 12V continuous or intermittent
• LED → D1, D2 (any color)

Float Switches

• Normally Closed (NC)
• Normally Open (NO)

Power Supply

• 12V SMPS or 9V Step-down Transformer

If Transformer is used:

• BR → W04/W10/DB107 (Bridge Rectifier)
• R5 → 1K (¼W)
• C1 → 470µF, 16V
• D1 → LED

Circuit Working ⚙️

The water level alarm uses two transistors (Q1 & Q2) configured as an OR logic gate:

• Low Tank Condition (NC Float Switch)
  • When water drops below the set level, the NC float switch closes, applying a positive voltage to the base of Q1.
  • Q1 turns ON, activating the buzzer 🔔 and LED D1.
• Full Tank Condition (NO Float Switch)
  • When water reaches the top level, the NO float switch closes, giving a positive signal to the base of Q2.
  • Q2 switches ON, triggering the buzzer 🔔 and LED D2.

👉 This ensures an alarm whenever the water tank is either empty or overflowing, preventing damage and wastage.

In the above circuit design, users are required to manually turn off the device whenever the alarm is triggered, and then turn it back on later to continue monitoring the tank level. This process is cumbersome and represents a significant drawback, making the circuit suitable only for project purposes and not for commercial use. However, by incorporating a momentary switch to silence the alarm without the need to power down the entire device, we can overcome this drawback. Here is a circuit to overcome this drawback and it can be used commercially as well.

Conclusion 🎯

The Full & Low Water Tank Alarm Project using BJT transistors is a beginner-friendly DIY electronics project that teaches transistor switching, float switch operation, and circuit logic. While it is ideal for learning and demonstration, with minor improvements, it can also be adapted for real-world water management applications in homes and industries. 🌍💦