What is Arduino?


It is a programmable open source board, whose low cost makes it ideal to start in automation or perform small domestic projects in electronics and robotics. It has purpose as a hobby and for anyone interested in creating objects of interactive environments this plate as it is able to receive information from the environment (sensors) and perform actions (actuators, motors, etc.), according to the program that is introduced with a computer, and that can run autonomously.

However, all the knowledge of electronic, automation, programming and telecommunication, can be applied directly and easily in case of having to use more expensive automaton, so Arduino is an excellent platform for practice and learning.


Although at first you can think that the obvious answer would be to buy a basic kit with an Arduino Uno, this is not the best option (of course it is not what I would do). Before launching to buy it there are several issues that should be taken into account. In this post, all these points are going to be worked out one by one to choose the best option. The main issues that should be taken into account are:

  • The type of project that want to carry out

  • The material that is available

  • The knowledge you have

  • The budget that is counted

The most normal thing to start is an Arduino UNO. This is the most standard model and it is the plate that will be used as usual. You will also find many tutorials and projects made with this plate. For other more complex projects that require handling a large number of motors or servo motors (robots, CNC machines, 3D printers) it may be necessary to move to a model with a greater number of outputs, especially analog outputs, in this case it is normal to use an Arduino MEGA or Arduino DUE.

The Arduino Uno card consists of an electric board that has an Atmega328 microprocessor; 14 digital input / output pins, of which 6 can be used as PWM outputs (pulse width modulation); 6 analog inputs; a 16 MHz ceramic resonator; a USB connection; a power connector; a microcontroller and a reset button.


Practically we will see the Arduino UNO card but in general the different Arduino cards are very similar. They have both output and input pins with which we can read our devices either a signal from a sensor or another parameter. Also send signals or data through the output pins which we will see how they work later to use the analog and digital actuators. Here is an image of the structure, remember that uses an ATMEGA328 microcontroller to operate all our devices.


Our card has 14 digital pins from 0 to 13, of which we can read and send digital signals ranging from 0 to 5 volts, also among those pins there are 6 PWN pins which we will see later, here a digital signal image:

It also has 6 analog pins, as its name says we can make analog readings equally from 0 to 5 volts. These pins can also be used as digital by means of the analogue digital converter. Here an analog signal image:

Remember that each pin works with voltages from 0 to 5 volts CC, in addition to the maximum current per pin is 40mA. If we use an actuator that requires more current than that delivered by a pin it is necessary to use a power transistor, but that you will see later.

The card consists of a voltage regulator, a 7805 connected to the Jack and the vin pin of the card with its respective protection diode, but this does not prevent caution and do not reverse the polarity in the pins of the power supply by a short circuit. 

Note: Never feed the Arduin board though the USB port since the USB ports of the computer deliver 5 volts and this signal does not go to the regulator, the card was not created to feed it in this way when wanting to execute a project.



It is important to follow these recommendations, as failure to do so could damage your development card:

  • Do not exceed current levels, both input and output, remember that Arduino cards deliver a maximum of 40mA per pin. Likewise, it also supports a maximum current of 40mA of reading, this means that it can turn on a led with a resistance of 220:

The output voltage of the pins of the Arduino card is 5V and the current that requires a led to turn it on is 20mA so, let´s see what resistance we need to turn it on correctly:

V = R x I
V / I
5V / 0.020A

Now we will see an example of the input current in our card, suppose we want to use a pushbutton, we will see what resistance we must put which will be the minimum, as we already know the maximum input current is 40mA:

V = R x I
V / I
5V / 0.040A

As we mentioned is the same value that must be placed to be at the limit of the capacity supported by the Arduino, but this is not advisable, so in most cases a resistance of 1KΩ to 10 KΩ is used, so our card works perfectly and calmly with 5mA.  

  • In external projects it is recommended to use a voltage source of 12V and be powered by the Jack of our card and not by the USB port, as already mentioned before.

  • Try that while our card is in operation that no liquid falls into it or any piece of metal that makes contact with each other, as it could suffer a short circuit and damage it.

  • If it is possible to acquire an acrylic case to keep it completely isolated and thus not suffer any damage.

  • If you use sensors, relays, servomotors, etc., use an external source to power them, remember that each pin in our card delivers a maximum of 40mA, if you overload the current will burn your card.

With these recommendations you will be able to work quietly with your card and create the projects that are presented below or those that you want.

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