How to build simple water overflow detector with transistor

Here it is illustrated how to build a simple water overflow detector circuit using a single transistor. The transistor is used as a switch which is turned ON when the water level reaches a certain level. A LED is connected to the transistor is then turned on to indicate that the water level has reached the top. 

The transistor used here is BC547. BC547 is a small PNP bipolar junction transistor (BJT) used as a switch in various electronic circuits. It is widely used in the switching and amplifying applications. In its simplest form, it can be used for switching a small load like an LED or to amplify a small signal like an amplified microphone or an amplified temperature sensor. It features a low power consumption, a high current gain, and a low voltage drop between its collector and its emitter electrodes. Additionally, it is easy to use and provides reliable operation. The BC547 can be used in a range of applications, such as light dimmers, switching circuits, and audio amplifiers. It is often used in small-signal switches, such as those found in smart home and automation products. Due to its low power consumption, BC547 is also used in battery-powered electronic systems. The device is also suitable for low-frequency switching applications such as remote control systems, motor drivers, and relay control circuits. Additionally, it can be used in small audio amplifiers, transistors, drivers, and signal converters.

Shown below is the water overflow detector circuit that was build with a single transistor and few components on a breadboard.

water overflow indicator breadboard

This simple water overflow detector circuit using a single transistor is designed to provide an alarm when water in a tank reaches the danger level. It works by detecting the liquid level and generating a signal when the water rises above the desired level. The circuit is easy to make and requires minimal components, making it an ideal solution for monitoring water levels.

The corresponding circuit diagram of the water overflow detector is shown below.

water overflow indicator circuit diagram

As you can see a single transistor BC547 was used. The transistor is used here as a switch. The LED indicator is connected as load in the collector side. The emitter is grounded. A 3V power supply from two 1.5V battery was used to operate the circuit. From the power supply one wire is dipped into the top of water container and the other is wire from the base connection is also dipped into the top of water container. When the water level is not touching the two conducting wires then there is no flow of current from the power supply to the base. As the water level rises up and touches the two wires then current flows from the power supply into the base and the transistors is turned ON. When the transistor is ON then there is flow of current from the power supply into the LED, then into the collector, into emitter and then ground and therefore the LED is turned ON.

The following shows animation of how the simple water overflow detector with a single transistor works.

simple water overflow detector animation

The following video demonstrates how the simple water overflow detector works.

So here it was shown how one can build a DIY water overflow detector using just single transistor, a LED, 1KOhm resistor and some wires. This circuit works on the principle that water conducts electricity and when there is water between two wires or rod then there will current flowing in the wire. So without water the connection between the wire is open and when there is water between the wire the connection is closed. Hence the presence and absence of conducting water makes it act like a switch. This switch is used to provide or not to provide current(voltage) to the base of the transistor and the transistor is effectively controlled by a water medium switch. This is an example of how one can use transistor as a simple switch.

The same water detector circuit can be used for plant moisture monitoring. The two wires have to be dipped into the soil of the plant. The wires however should not be placed too far from each other. Then when there is no water(no moisture) in the soil the water detector LED is turned OFF. When we water the plant, soil moisture level is increased and there is conduction electricity between the two wires and the due to this there is base current and the transistor is turned on and therefore the LED is turned ON. So here when the LED is  ON, it indicates that the plant has enough water.

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