12 Volt Voltage Regulator – HomeMade

12 Volt Voltage Regulator
12 Volt Voltage Regulator

Many times we need a constant voltage for various tasks or making electronics projects. If the voltage supplied to the electronics device is fixed as required, then the device can work properly. For example, if a 12-volt device is given a 10-volt supply, the device may work, but will quickly damage. Again if the supply is given up to 20 volts, then the device will work fine, but also due to excessive voltage, the device will be damaged internally. So as a solution, if you want to use the device for a long time with good performance, a 12-volt voltage regulator will be required.

Various types of voltage regulator ICs are available in the market to keep the voltage constant. One of the most widely used ICs is the LM78XX or L78XX series IC. There has no difference between the working principle of LM78XX and L78XX, just different manufacturing companies. And there are many ICs in this L78XX series, such as: L7805, L7806, L7808, L7810, L7812, L7818, and L7824. They are widely used in different devices and projects, depending on the need. In this post, we will build a 12-volt voltage regulator and discuss its various aspects. Since we are going to build a 12-volt voltage regulator circuit, so today we will work with L7812 IC.

Required Equipment:

Required Equipment
Equipment Table

Circuit Diagram of 12-volt Adjustable Voltage Regulation.

A Circuit Diagram of 12-volt Adjustable Voltage Regulator
Circuit Diagram of 12-volt Adjustable Voltage Regulator

The above figure shows a 12-volt fixed voltage regulation circuit diagram. This regulator circuit can be designed in different ways. But in this post, we will deal with this circuit.

Analysis of The Circuit Diagram:

To build this 12-volt voltage regulator, we need a Step-Down Transformer, Diode, Capacitor, Resistor, LED, and a Voltmeter. Everything in detail has been discussed below.

Step-Down Transformer
Step-Down Transformer


A Step-Down Transformer is used here which converts approximately 220 volts to 20 volts. The input of the transformer will be directly connected to the 220 Volt line. Its output can have 2 or 3 wires.

1N4007 Diode


Here four 1N4007 diodes are used to construct a full bridge rectifier. As we know that the rectifier circuit converts AC to DC.

As a filter the Capacitor is use in the circuit.


Then a capacitor (C 1) is used with a value of 1000uf and 35 volts. We know that rectifiers can convert AC to DC, but it is unable to provide pure DC. Basically, the rectifier-converted DC contains some alternating current (AC). Basically, the capacitor works here as an AC filter. In the case of the rectifier circuit, the capacitor is connected parallel with the output of the rectifier to convert that impure DC to pure DC.

Red LED use as indicator


A red LED is used as an indicator. A 1-kilo ohm resistor is connected in series with the LED which protects the LED from the flow of overvoltage.

It is a picture of Regulated IC L7812
Regulated IC L7812

Regulated IC7812:

Regulated ICs basically maintain the voltage at a fixed output. For example, if a 14 to 35-volt DC supply is given in the input of 7812 IC. It provides a 12-volt pure DC supply in the output.

There has an available IC of model LM7812 or L7812 in the market. Any of them can be used as a regulated IC. We have used L7812 IC here.

In this circuit, when from the capacitor (C1) a voltage between 14 and 35 volts at will enter in the input of L7812, then the L7812 IC will provide a stable 12 volts at the output.

Working of L7812 IC:

Picture is about the Pin Configuration of 7812 IC
Pin Configuration of 7812 IC

The 78XX IC is a series regulator, a three-terminal device that provides a constant voltage at its output. 78XX, where the last two digits indicate the value of the voltage to be regulated. For example, the +12V regulator is identified by the 7812.

L7812 is used here, it is a Fixed Positive Voltage Regulator IC. In L7812 IC, Pin no-1 is the input that is used to give input supply in the IC, and Pin no-2 is ground it normally connects with the ground. Pin no-3 is the output Pin, from where we get output.

Pin Configuration of 7812 IC:

Positive voltage should be applied to pin 1 of this IC and negative voltage to pin 2. Then negative voltage from pin 2 and positive voltage from pin 3 will be available as output shown in the above picture.

Here the input voltage range of 7812 is 14 volts to 35 volts DC. If a voltage higher than this is supplied to this IC, it will be destroyed. The 7812 IC can supply a maximum current of 1.5 Amp. A constant +12V is available at the output of this circuit. But if the input voltage is high, it tends to heat up a lot, so a heat sink is used to keep it cool. Its output will be pure DC.

Note:- This fixed voltage regulation circuit is converted from AC to DC with the help of 4 diodes which is called bridge rectification. But if you have a DC source like a battery or DC adapter whose voltage range is between 14 volts and 35 volts, then you can directly apply this voltage to the input of LM7812, and you can get constant voltage at the output.

Process of the Circuit Connection:

In a simple six-step, you can build a 12-volt voltage regulator. To build your own voltage regulator, read this procedure clearly. Here you will see seven steps, but six steps use to build the regulator and the last step is just how to measure voltage.

In the post 12 volt voltage regulator this picture is about Setup the Transformer
Setup the Transformer

Step- 1: Setup the Transformer:

Firstly, select the primary and secondary sides of the transformer. A small mistake can cause big damage or an accident. Then connect a plug with the primary side, and the secondary side will be connected with the rectifier.

This picture is about Bridge Rectifier Creation
Bridge Rectifier Creation

Step- 2: Bridge Rectifier Creation.

Secondly, we will make a bridge rectifier using four diodes. A bridge rectifier is constructed using D1, D2, D3, and D4 in the figure above. Here diode D1 and D3’s anode terminals and D2 and D4’s cathode terminals are connected together.

Then connect the two output wires of the transformer between the junctions point of diodes D1 & D2, and D3 & D4. As respectively shown in the above figure.

As per the bridge rectifier specification for this regulator circuit, the junction point of the D1 & D3 diodes will be considered the negative output terminal, and the D2 & D4 junction point diodes will be considered the positive output terminal.

Picture is about Capacitor Connection
Connect Capacitor

Step- 3: Capacitor Connection.

Now the positive output and negative output terminals of the rectifier will be connected to the positive and negative terminals of the capacitor (C1).

The picture is about Indicator Connection
Indicator Connection

Step- 4: Connect Indicator.

Now connect a resistor to the positive end of the capacitor (C1). Then connect a LED as an indicator. Here we use a red LED.

Note that the resistor and LED are connected in series with each other and, the series combination of the resistor and LED will be connected parallel with the capacitor (C 1).

In the post 12-volt Voltage Regulator this picture is about Connect Regulated IC
Regulated IC Connection

Step- 5: Connect Regulated IC.

As we know, in IC L7812, pin 1 is the input, pin 2 is the ground, and pin 3 is the output. So connect pin 1 to the positive terminal of the capacitor and pin 2 connects to the negative terminal of the capacitor.

Now pin 3 will be considered as the positive output of the regulator and pin 2 will consider as the negative output of the regulator. These two outputs are the final output of our regulator.

Output of 12-volt Voltage Regulator
The output of a 12-volt Voltage Regulator

Step-6: Mesure With Voltmeter.

Now, if we connect a voltmeter with the positive & negative terminal of the regulator, we can see a constant +12v coming at the output, shown in the above picture.


  • Care must be taken when applying an input voltage to the transformer so as not to cause shock.
  • DC mode must be selected while setting the range of the meter. Otherwise, the meter may be damaged.
  • When installing the diode, its Anode Cathode should be properly checked or the output will not get any voltage.
  • When connecting the capacitor, the polarity must be observed, if wrong, the capacitor may burst.
  • The value of the capacitor should be one and a half times the input voltage.
  • A heat sink must be installed when using L7805 IC.

Applications of Voltage Regulators.

A voltage regulator is one of the most important components of an electronic circuit. Also, there have many applications for a voltage regulator. And they play important roles in its safe and consistent operation. such as-

Mobile phone charger is one of the most common examples. In this case, the adapter is supplied with an AC signal, but the output voltage signal is a regulated DC signal.

To provide desired output voltage every power supply in the world uses a voltage regulator. Such as Computers, laptops, televisions, and all sorts of devices are powered using the method.

The operation of small electronic circuits relies on regulators. Because the slightest fluctuation of voltage signal can damage the components of a small circuit such as ICs.

Voltage regulators play an essential role in the operation of power generation systems. For example, a solar power plant generates system is a system that generates electricity based on the intensity of sunlight. This system required a regulator to ensure a regulated constant output signal.

In heavy machinery, very high voltage regulators use power electronics circuits with high power ratings in industrial settings.



This circuit we have tested in Lab, it’s 100% workable and proven. Because of some technical issue, we can’t provide the video but hope as soon as possible we will provide the video. For this time we provided pictures that we have done in proteus. If you have any doubts or any questions ask in the comment section.


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