Now we will see how the transistor works as a switch, here we are using an NPN transistor. When the base current is removed the transistor will turn off completely, This stage is known as the Cut off Region.This stage is named Region of Saturation. If this transistor is fully biased then a maximum of 100 mA can flow through the collector and emitter.Conclusion with statement 2 and 3 is, 0.5 mA base current IB drive 10 mA Collector current IC and 5 mA IB can drive 100 mA IC.To bias a transistor we must supply a base pin with current, The current (IB) is limited to 5 mA.The maximum current able to flow through the Collector pin is 100 mA, We can not therefore connect loads which consume more than 100 mA using this transistor.Gain value of BJT BC547 is between 110 to 800.It is mainly used for signal amplification.In NPN majority charge carriers are electrons while in PNP majority carriers are holes. Most common category of Transistors is BJT – Bipolar Junction Transistor.Īs these are semiconductor devices, they are of two types one is NPN and other is PNP. It’s an amazing DIY project for students.Transistor is a three terminal semiconductor device which is used in switching and to amplify the base signal but now they are mostly used in embedding integrated circuits. As the water level in the mug or tank rises the other base terminals also gets connected to the battery via water and thus other LEDs and buzzer finally starts glowing. This leads to the switching of the transistors to ON state. When we dip the base terminals of all the transistors one by one in water and also add the+Ve terminal of the battery to water tank, a current in micro Ampers starts flowing via base terminal. When we power the circuit via a 9V or 5V battery the circuit is in off state there is no current flow through the transistors and the remaining circuit. The 4th transistor is used to power the buzzer when the water level rises to its sensor. The base of all the transistors is dipped into the water via a 220Ω resistor. are transistors with an arrow showing emitterĪll the emitters are connected to -ve terminal of the battery and all the collectors are connected to LED ( except 4th which is connected to the buzzer) via 220Ω resistor. Here is the circuit diagram of water level indicator using transistor bc547 Components:ģ.) Standard PCB board (or you can use breadboard).ħ.) Soldering iron, soldering wires, and flux. To start with your water level indicator mini project you should have the following components and tools. Here a fraction of current(<2% of total current) must flow through the base if it does not then it will not work.ĭue to some dissolved mineral and impurities water has some conductivity due to which a very small amount of current( in micro Ampers) flows through it. So when a signal is applied at the base the transistor acts as a closed switch and when no signal is applied it acts as an open switch. When we connect emitter and collector of a BJT transistor to negative potential (-) and apply a positive potential to base, current starts flowing from collector to emitter via base if we remove the positive potential from the base then current also stops flowing. In this project, we will use the switching property of transistors, which States that, Here we are using an NPN bipolar junction transistor(BJT) bc547. Transistor-is a device which is used for amplification or switching of electrical signals.
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