Electronic projects with 2n2222 Transistor or BC547 Transistor- BC547 NPN Transistor is of the most popular Bipolar Junction Transistors. So many amazing electronic projects can be built using this transistor. Recently some electronic projects got viral which were completely based on the BC547 Transistor. In this article, we will develop the same electronic projects using the most popular 2n2222 NPN transistors. I will also explain the working principle of each electronic circuit, and we will test each circuit on breadboard. For step by step explanation you can watch a video tutorial given at the end of this article.
The 12V and 5V power supply PCB board used in this video is sponsored by the PCBWay Company. PCBWay is quite professional in the field of PCB manufacturing; you can try their services at extremely low prices, Only 5 dollars for 10 PCBs and 30 dollars in total for 20 PCBs assembly, besides this the new members also get a 5 Dollars bonus. The Gerber files of the PCB board used in this project can be downloaded from the PCBWay official website.
We will make the following four projects using the 2N2222 NPN transistors.
- Light meter
- Non Contact AC line Voltage detector/tester
- Water level monitoring
- Portable security system using Mini PIR Sensor
The same electronic projects can also be developed using the BC547 instead using the 2n2222 NPN transistor. So it really doesn’t matter whether you want to use 2n2222 or BC547 NPN transistor. You can update the circuit at anytime, you can replace the 2n2222 NPN transistors with the BC547 and it will have no negative effect on the project.
Without any further delay let’s get started!!!
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Number 4 on the electronic projects list is the Light Meter which is one of the viral projects. The brightness of the LED depends on the light falling on the LDR which stands for Light Dependent Resistor. I did one modification in this project which is I added a potentiometer so that the sensitivity can be controlled as per the requirement.
Let’s have a look at the Circuit diagram and understand how this project works.
So first let’s start with the 5V regulated power supply based on the LM7805 Voltage regulator. The positive and GND pins of the DC female power jack are connected with the input and middle legs of the 7805 voltage regulator. Two 470uf capacitors are connected at the input and output sides of the voltage regulator. A 330 ohm resistor is connected in series with a 2.5V LED. This is a current limiting resistor.
An LDR and a potentiometer are connected in series which makes a voltage divider. LDR is also a variable resistor but its resistance changes as the light falling on the LDR changes. So this way we always get a variable voltage which completely depends on the light intensity. The purpose of using the Potentiometer instead of using a permanent value resistor is that we can change the resistance by rotating the knob of the potentiometer.
A wire from the middle of the voltage divider circuit is connected with the base of 2n2222 NPN transistor. The varying voltage which is coming from the voltage divider actually controls the 2N2222 NPN transistor. The emitter of the transistor is connected with the ground while the collector of the transistor is connected with the cathode pin of the LED which is connected in series with a 330 ohm resistor. This is a current limiting resistor. This circuit is powered up using the 5 volts from the 5v regulated power supply.
Number 3 on the electronic projects list is the Non Contact AC live Wire Tester. This circuit is quite sensitive that even it can detect my hand. Let’s have a look at the circuit diagram and discuss how this project works.
The 5V regulated power supply remains the same. A coil is connected with the base of 2n2222 NPN transistor. The transistors T2 and T3 makes the Darlington pair. A Darlington Transistor configuration, also known as a “Darlington pair” or “super-alpha circuit”, consist of two NPN or PNP transistors connected together so that the emitter current of the first transistor T3 becomes the base current of the second transistor T2. A darlington emitter follower is two transistors operating as one. Both collectors are tied together. The emitter of the first is connected to the base of the second. This means that the overall current gain, β is given by the gain of the first transistor multiplied by the gain of the second transistor.
So the transistors T2 and T3 drives the Transistor T1 which turns ON and Turns OFF the 5v buzzer.
Number 2 on the electronic projects list is the Water level monitoring. I really liked it while making this small project. The final red led can be replaced with a relay which can automatic turns OFF the Water Pump. Now let’s have a look at the circuit diagram.
This circuit is also powered up using the 5V regulated power supply. The 5V wire from the Power supply is dipped in the water along the 4 wires coming from the bases of all the 2n2222 NPN transistors. For more levels you can simply increase the number of circuits. All the circuits are exactly the same. Each LED is turned ON as the water container is filled.
Number 1 on the electronic projects list is a Portable security system based on the mini PIR sensor, 2n2222 NPN transistor, and a 5V buzzer. This is such an amazing low cost security system, there is no need for the Arduino Board or any other microcontroller board. This mini PIR Sensor is used with the BC547 or 2N2222 NPN transistor to control a buzzer. The buzzer can be replaced with a 5v relay. Now let’s have a look at the circuit diagram.
This circuit is also powered up using the 5v regulated power supply. The + and – pins of the mini PIR sensor are connected with the 5V and Gnd. The Out pin of the PIR sensor is connected with the Base through a 10k resistor. When the PIR sensor detects a human it gives 5 volts on the base which turns ON the transistor and as a result the buzzer is activated.
This mini PIR sensor has a total of three male headers which are clearly labeled as + which will be connected with the +5 volts, OUT which will be connected with the Base of 2n2222 NPN transistor, and a minus pin which will be connected with the Gnd. Now let’s do the connections on a breadboard.
The same electronic projects can be built using the BC547 Transistor. So, this is how easily cool electronic projects can be designed without using a microcontroller.