Notes sur Arduino

En cours de rédaction


En ce qui concerne les alimentations "externes", la documentation disponible sur le site d’Arduino stipule :

The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.

En pratique, les utilisateurs de l’Arduino signalent qu’une tension d’alimentation de 12 Volts peut endommager l’Arduino.

La tension d’alimentation (via la prise Jack ou les PINs Vin et GND) conseillée est de 9 Volts.
Les PINs d'entrée/sortie

L'Arduino dispose de :

Entrées/sorties digitales

La documentation officielle de l'Arduino stipule :

each of the 14 digital pins on the Uno can be used as an input or output, using pinMode(), digitalWrite(), and digitalRead() functions. They operate at 5 volts. When configured as OUTPUT, each pin can provide or receive a maximum of 40 mA (WRONG!) and has an internal pull-up resistor (disconnected by default) of 20-50 kOhms.

Pins configured as OUTPUT with pinMode() are said to be in a low-impedance state. This means that they can provide a substantial amount of current to other circuits. Atmega pins can source (provide positive current) or sink (provide negative current) up to 40 mA (milliamps) - WRONG! - of current to other devices/circuits.

Attention : la valeur annoncée de 40mA représente la "Absolute Maximum Ratings". Or, si vous consutez les documents ci-dessous :

A la page 303 des Spécification du microcontrôleur ATMEGA328P-PU, vous pouvez lire :

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Pour rester dans la marge de sécurité :

Lorsqu’une PIN est configurée en sortie:

Il faut veiller à ce que l’intensité du courant qui transite par une PIN digitale configurée en sortie ne dépasse pas 20 mA.

If the pin has been configured as an OUTPUT with pinMode(), its voltage will be set to the corresponding value: 5V (or 3.3V on 3.3V boards) for HIGH, 0V (ground) for LOW.

Lorsqu'une PIN en configurée en entrée, son impédance est extrêmement forte.