How an ardunio card works? How to choose the right card?


The arduino card is a small programmable electronic board with enough computing power to control your components and retrieve values from a sensor. It is intended to beginners or amateur which want to do electronic project easily. The arduino brand is composed of different cards: Uno, Mega, Nano…

The Arduino card has free sources, that’s mean you can build yours or sell it by yourself.

Finally, the Arduino card use Arduino IDE software to program it. In this software you will use the Arduino language, a derivative of the C language.

What is Arduino?

To know more about the history of Arduino brand and how to start well on Arduino electronics you can read our course about it.

Board functionning

The arduino card is a small electronic board equipped with a processor.The one will be used to read the input values such as a value of a sensor and control components such as a servomotor.

Here is an example of what you can do with this card. The project that we do is a photo-resistor which will determinate the power of the led thanks to the outside luminosity:

To do this project, you will need to program the Arduino board:

  • Read the value of the photo-resistor
  • Convert the value of the photo-resistor to adapted it to the power of the led
  • Turn on the led with the adapted power

The program has to be upload to the Arduino board. To do that you will need Arduino IDE software which will translate your program in a assembly language and upload it in the Arduino card

How the Arduino board interact with the others components?

It’s a question important to ask: How the Arduino board can read the values of a sensor or know that a push button has been pushed.

As every computer, an Arduino card works with 0 and 1.

For the Arduino card:

0 => Low state : 0V
1 => High state : 5V or 3.3V

Fro our project, we will use a photo-resistor. Many sensors retrieve the value measured in a value in tension. This tension is a value from 0V to 5V. This is called an analogue value. To be understood by the Arduino card, this value has to be converted in a digital value.

USB connection:

  • Power the arduino board in 5V
  • To upload the program in the Arduino card


  • To power the Arduino board with battery. Thanks to that you can have an autonomous Arduino board, which is not the case with the USB wire which has to be connected to the computer.

Analogue pin:

  • Can be used to plug sensors and retrieve the value in tension

Digital pin:

  • To control components such as servomotor, stepper motor…

LED pin 13:

  • Led which is linked to the pin 13 of the arduino UNO card. This led turn on when the pin 13 is high state.

RESET button:

  • To restart the program inside the card.

TX/RX pins:

  • The pins RX and TX permits to the arduino card to communicate with others devices such as components or a computer. Theses both pins don’t have the same role of the digital pins therefore they are not used to control a component.
    The TX and RX pins are used during an USB connection with a computer.


  • Led which blink when the TX and RX liaisons is used. Th LED are used when the program is uploading.

Power LED:

  • The power LED is turned on when the Arduino card is turn on. It is used to know when the Arduino card is working.


  • This pin has an analog-to-digital converter. It is used to follow a signal from 0V to 1.5V.


  • Send a reference voltage to the card. For the arduino card it’s 5V.

VIN Pin:

  • The VIN pin is used to power the Arduino card instead of using the USB liaison.


  • The ISCP pin is used to load the bootloader at the start of the arduino board is the bootloader is missing or broken.


  • To store and execute the program

Comparing the different card

There are different arduino cards, but some of them are similar. Therefore the description of the pins made just before can be adapted to each Arduino card.

Nevertheless, through the year, new Arduino cards are created to corresponds of the different needs. We will make a presentation of the different Arduino card with their specifications.

a) Arduino Uno

The arduino uno is the most known of the Arduino card. It has been created just after the Wiring Arduino card. The Arduino wiring is not longer sell it on the market, therefore the Arduino Uno card is the most older card from Arduino still possible to buy.

This is the table of its characteristics:

Arduino Uno Size Weight Power Analogue Pin Digital Pin Microprossor Where to buy?
74 x 53 x 15 mm 25 grams USB connector 5V  Jack 7-12V 6 inputs 14 inputs ATMega328 clocked: 16 Mhz amazon

As you can see the Arduino Uno card has many advantages. It’s lightweight with a tiny sized that can be used in an embedded system with a reasonable price. The most important advantage of this card is that it is the most used of the Arduino cards, therefore you will have a lot of resources to help you. We advice you this card if you want to begin in electronics.

Nevertheless if you want to do more complex project, you will probably need more Analogue pins to read the values of your sensors. In this case you will need the Arduino Mega card!

b) Arduino Mega

The Arduino Mega card has 10 analogue pins more than the Arduino Uno card, which can be really useful if you want to read the value of many sensors.

Arduino Mega Size Weight Power Analogue Pin Digital Pin Microprocessor Where to buy?
101.52 x 53.3 mm 37 grams  USB connector 5V Jack 7-12V 16 inputs 15 inputs ATMega2560 clocked at 16 Mhz amazon

One of the disadvantages of this card is the weight and the size of it. In fact, this is the most sized and the heaviest Arduino card. It is not appropriate for the embedded system such as a drone for example. For this kind of project you will need a lighter and a smaller size Arduino card such as the Arduino nano card.

c) Arduino Nano

The Arduino Nano has been created in 2008. This is the smallest and the lighter Arduino card. It can make different project that can’t be possible with an arduino Uno or an Arduino Mega because of its size and weight. The Arduino Nano can useful for all electronics project that can fit in one hand or a lightweight project, such as a radio, an alarm clock, a power bank or a drone…

Arduino Nano Size Weight Power Analogue pins Digital pins Microprocessor Where to buy?
18 x 45 mm 7 grams mini USB connector from 7 to 12V 8 inputs 14 inputs ATmega328 : clocked at 16 Mhz amazon

One the disadvantage of the Arduino card is that there isn’t jack connector. It can be more difficult to do an autonomous project because it will be more difficult to plug a battery on it.

d) Wifi Arduino Uno

The wifi Arduino Uno has been created because a lot of project need a wifi connection. It can be useful if you want to communicate with your phone, your Arduino card, your computer…

You can also use the Arduino Uno card and the ESP32 Wifi module. But the disadvantage of this solution is it’s used of the digital pins. Therefore the Wifi Arduino Uno has fix this gap.

Arduino Uno Wifi Size Weight Power  Analogue pins Digital pins Microprocessor Where to buy?
68.6 x 53.4 mm 25 grams mini USB connector and Jack  from 7 to 12V 6 inputs 14 inputs ATmega4809 clocked at16 Mhz amazon

One of the disadvantage of the Wifi Uno Arduino is that is has a different microprocessor than the Arduino Uno. Therefore you can’t use all the information dedicated tot he Arduino Uno on the web. Moreover you will find less informations about the Arduino Uno wifi than the Arduino Uno and Esp32 module. That’s why we don’t advise you this card if you begin on electronics!

Arduino' s concurrents

The Arduino environment has been created as an open source, that’s mean anyone can create it’s own card. Thanks to that Arduino’s concurrent has created their own cards to fix problems that Arduino can have or to create a cheapest card.

The disadvantage of theses concurrents cards is that you will have difficulties to find documentation or information for those who begins.

a) NodeMCU

The Node MCU card is a programmable board easy to use.It looks like an Arduino Nano board, but there are an additional Wifi module. This card is compatible with Arduino IDE, which easier to use.

The NodeMCU card works with micro USB wire to upload the program on the card and to power it. The card is sell at 6.99 dollars which less expensive than an official Arduino Nano board.

the NODEMCU has 12 digital pins which is almost the same as the Arduino Nano board. Nevertheless, the NodeMCU board doesn’t have Analogue pins, which can be a problem if you want to read a value from a sensor for example.

We recommend you this card if you want a lightweight board with a Wifi module. Nevertheless this card has not a lot of documentations on the internet compared to the Arduino Uno.

b) Teensy 4.0

The Teensy is a programmable board close the Arduino Nano because like the NodeMCU card we can both use it with Arduino IDE. The Teensy card has a RTL module which allow to have the time even if the card is power off. You have to add a round stack to keep the time. This card can be really useful to do an alarm clock for example and to have the right hours and minutes after powering off the alarm clock.

The Teeny 4.0 has a microprocessor of 600 MHZ, which is really quick compared to the Arduino card!

Furthermore, the frequency is adapted with task we need, therefore for a small task therefore it won’t consume a lot of energy.

Finally, the Teensy 4.0 has 9 pins the Analog and 9 pins for the digital which is enough  to control your component and read the values from a sensor.

c) Conclusion of the Arduino’s concurrent

As we have seen, using a concurrent of Arduino can be really useful if you want ot do specific project, such as a project with a Wifi module or to keep the time. Theses cards can be really useful in theses cases because it will be cheaper and lightweight than an Arduino card plus an external module.

Nevertheless the disadvantage of this card is that there not a lot of information about it, therefore you have to know how to use it by yourself.