This is a circuit that tells you how much water is in a tank.
It beeps like an alarm when the water level gets too high or too low.
We will build one using transistors electronic parts that will only beep when there is water between two metal sensors placed inside the tank.
This post will show you how to make this circuit including all the details what is good about it and what is not so good.
Circuit Working:
Parts List:
| Components | Value | QTY |
| Transistors | BC547, BC557 | 1 each |
| Resistor | 10Ω, 1/4 watt | 1 |
| Speaker | 8Ω | 1 |
| Power Source | +3V to 6V | 1 |
| Water level probes | Any Metal probes | 2 |
Let us begin by understanding the connections and components used in this circuit:
BC547 Transistor:
Emitter E of the BC547 transistor is connected to the +3V power source.
Base B of the BC547 transistor is connected to the collector C of the BC557 transistor.
BC557 Transistor:
Collector C of the BC557 transistor is connected to the ground 0V line via a 10 ohm resistor.
Speaker:
The 8 ohm speaker is connected between the emitter E of the BC547 transistor and the ground 0V line.
Water Level Probes:
The +3V power source and the base B of the BC547 transistor serve as the probes for detecting water levels.
Formulas:
You may use the following fundamental circuit layout and associated calculations to construct a water level indication buzzer circuit:
BC557 Base Resistor Calculation:
In order to guarantee correct functioning and safeguard the transistor the base resistor for the BC557 transistor is normally designed to restrict the base current to a safe level.
R1 = VCC − VBE / IB
where,
- The supply voltage 3V is VCC.
- The base emitter voltage drop of the BC557 transistor is represented by VBE which is usually 0.7V.
- Based on the intended collector current and the transistors current gain.
- IB is the base current needed for the transistor to operate properly.
Speaker Current Limiting Resistor:
To safeguard the transistor BC547 and the speaker itself, resistor is used to control the amount of current that flows through the speaker.
R2 = VCC / Ispeaker
where,
- The supplied voltage is VCC is 3V.
- The speakers current rating Ispeaker is typically between 20 and 30 mA for tiny speakers.
For building the circuit these formulas offer a foundational framework.
Depending on particular component datasheets and intended circuit performance actual resistor values and transistor properties may differ.
Verify everything with actual testing and make any necessary adjustments.
Working of the Circuit:
The BC547 transistor is used as a switch to control the flow of current in the circuit.
When no water is detected between the probes the base of the BC547 transistor is not conducting and the transistor remains in the off state.
The BC557 transistor acts as a voltage divider with the 10 ohm resistor.
It is connected to the ground and provides a path for current to flow when water is detected between the probes.
The 8 ohm speaker is connected between the emitter of the BC547 transistor and the ground.
When water comes into contact with the probes, it completes the circuit allowing current to flow through the BC547 transistor which then activates the speaker.
Advantages:
Disadvantages:
- Limited sensitivity and accuracy.
- Requires manual monitoring.
How to Build:
- Gather all the components mentioned above.
- Place the BC547 and BC557 transistors on the PCB.
- Connect the emitter of the BC547 transistor to the +3V power source.
- Join the base of the BC547 transistor to the collector of the BC557 transistor.
- Connect the collector of the BC557 transistor to the ground line using a 10 ohm resistor.
- Attach the 8 ohm speaker between the emitter of the BC547 transistor and the ground.
- Use the +3V power source and the base of the BC547 transistor as water level probes.
Note:
Ensure that the circuit is well connected and free from any loose connections.
Conclusion:
The water level indicator buzzer circuit provides a simple solution for detecting water levels in number of applications.
You can successfully build and implement this circuit for your own requirements if you understand the connections and how each component functions.