LM7805: all about the voltage regulator


El LM7805 is a voltage regulator, But not to be confused with the voltage divider which we already talked about in another of our previous articles. In addition, it is not just any voltage regulator, but it is one of the most used by makers and in DIY projects of all kinds. Its function, as its name suggests, is to regulate the voltage signal of a circuit in which it is integrated.

A component that is not always well valued and that, on occasions, is dispensed with for many projects. But that is quite important if you want a stable voltage signal. Especially important is the LM7805 when creating power circuitry for our circuits. For example, to create a homemade power supply with certain characteristics, one of these regulators should not be missing.

What is a voltage regulator?

LM7805 internal circuit

Un voltage or voltage regulator like the LM7805 is a device that is capable of modifying a voltage signal it gets at its input and deliver a different voltage signal at its output. At that output, the voltage is usually lower and with certain characteristics that are required to avoid risks or for the circuit to which it is fed to function properly, if it is sensitive to voltage variations.

To make this possible, the voltage regulator has an internal circuit with a series of resistors and transistors bipolar connected in such a way that it allows to fine tune the voltage signal in a suitable way. You can see the internal circuit that is integrated into the package of this device in the image above.

Release there are many different voltage regulatorsyes, most of them quite cheap. Apart from the LM7805 you will also find the 7809, 7806, 7812, etc., from the 78xx family. Although in this article we will focus on the 7805, being one of the most popular.

La difference between voltage regulator and divider tension is clear. The divider divides the input voltage into several voltages lower than its output, but does not correct the signal for the voltage. On the other hand, in the voltage regulator, a similar voltage is obtained at the output, but with the signal much more precise than that obtained at its inputs.

Voltage regulator applications

Signal from a power supply

As you can imagine, an IC like the LM7805 can be used for many things. For example, power supplies they usually integrate one of the 78xx series. In fact, the power supply, as we explained in a previous article, is made up of several stages:

  • Transformer: it is possible to transform the input voltage of 220v to a suitable one of 12, 6, 5, 3, 3.3 or whatever value.
  • Bridge rectifier: then that signal will have the appropriate voltage, but it will continue to be an alternate signal, after passing through this bridge the negative signal is avoided.
  • Capacitors: now the signal has the shape of mounds, that is to say, of some voltage impulses that when passing through the capacitor will be smoothed, being almost a straight line.
  • Tension regulator: finally, the regulator will refine that signal to make it completely flat and stable, that is, to make it a direct current signal.

Other application example of a voltage regulator would be to feed certain integrated circuits that cannot be fed with a signal that exceeds a certain figure. For example, imagine a sensor or chip that cannot go beyond 3.3v of power. Well, in this case, a regulator could be used to avoid risks of exceeding that barrier. All excess energy is dissipated as heat by the 78xx.

Related article:
LM317: all about the adjustable linear voltage regulator

7805: pinout and datasheet

Pinout of 7805

There are various manufacturers of the LM7805, such as STMicroelectronics, TI, Sparkfun, etc. In addition, you can find it both in its traditional package and in a module to make it easier to integrate into your projects with Arduino. Depending on the model you have bought, I advise you to access the official website of the manufacturer to check the characteristics in the specific datasheets for the model. Remember that although they are all similar, there may be some changes from one manufacturer to another.

If you buy it in TO-220 package, you will find a 3-pin pinout. They are numbered and the one corresponds to the voltage input that you want to modulate, the central two is GND or ground (the common one), the third pin is for the output of the already regulated voltage, that is, the stable signal that we will use as supply of the sensitive circuit that we want to make work. But you will have to add some extras such as capacitors as recommended by the manufacturer so that the output is adequate.

LM7805 Arduino Module

In the case of the module, it is a little more expensive, but it may make things much easier for you. It includes the 7805 device and also other elements that you they will make it easier to use with Arduino. You don't need extra capacitors or anything else. In addition, it includes a heatsink to maintain the proper temperature by dissipating the heat generated by the 78xx and two connection cards for the input and output (Vcc and GND at each end), facilitating its implementation.

Other models

HR differences between the different models available in the 78xx series of voltage regulators is quite simple. The figure that accompanies this family indicates the maximum voltage supported by each regulator. For example:

  • LM7805: 5v and 1A or 1,5A in some cases.
  • LM7806: 6v
  • LM7809: 9v
  • LM7812: 12v

Dónde comprar

If you want to buy it, you have it available on Amazon, in addition to other specialized electronics stores. The two variants that you can buy are:

  • No products found. In package TO-220 for € 4 you can buy 10 of these devices.
  • LM7805 in module for just under € 6 per unit.

As you see, they are pretty cheap devices...

Integration with Arduino

If you think about it integrate with a project with Arduino or the Raspberry Pi or another type of board, There is no problem. You will not have to use specific libraries as with other modules, nor will you have to add extra code in your Arduino IDE, since this 78xx is self-contained and simply dedicated to modifying the voltage input signal. You should only have the necessary electronics knowledge to place it in the right place on your circuit ...

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