On the left, on the contrary, the direct current model, in the line with the output values shows in an equally clear way +5 V 2A, moreover the symbol “═” graphically points to the direct current finally, in these power supplies, the voltage polarity is always indicated on the output JACK in this case the graphics represented on the tag indicates that the positive pole (+) is connected to the central part of the jack while the negative pole (-) is connected to the external part. In some cases, in the place of the AC abbreviation, the symbol “~” may be found, and it still means “alternating current”. In the alternating current model, shown on the right side of the figure, the line with the indications concerning the output says: AC 12 V 500mA 6VA, that respectively represent: alternating current, maximum output load and power, expressed in VA (that can always be obtained by means of the P = V*I formula). Now you have to fool around a little to connect up to 5V someplace on the board.Comparison between power supplies operating on AC and DCĪs it can be noticed from the symbols found on the respective tags, it is quite simple to distinguish the two models, even though they are physically similar. If the Unos had an option to plug on a jumper to allow 5V to go right from the barrel jack to the 5V bus, that would have been handy, especially with 5V wallwarts so inexpensive. The regulator used really needed a diode to feed the output back into the input when there was no barrel jack power. Megas had a problem for quite a while with the regulator being back driven from the 5V header pin. With a 9V adapter, it would overheat and shutdown/restart. I did take it to work to let it scroll a really long message stored in EEPROM, close to 1000 characters in a rambling message. For example, four MAX7219s driving 8x8 LED matrixes as I did here. With a 9V or 7.5V source, one can do quite a bit. With a 12V source, yes, current should limited to avoid overheating/shutting down the regulator. One just has to be careful on the load, but it can quite a bit more than just an LED or two. If you want to power it from 12 V or a car system, you need a 5 V switchmode "buck" regulator to supply the 5 V. The "5V" pin is not by any means an output pin, if anything a "reference" pin but most certainly the preferred pin to which to supply a regulated 5 V.Ī practical power supply for the Nano (or UNO, Pro Mini, Leonardo etc.) is a "phone charger" with a USB output connector for 5 V, generally up to a couple of Amps though you can not feed more than 500 mA through the USB connection. Powering via the "barrel jack" or "Vin" connections is asking for trouble. The on-board regulator might be able to power a few other things if it had a heatsink, but on the (older) Arduinos, it does not. This is because the on-board regulator is essentially capable of powering only the microcontroller itself and no more than a couple of indicator LEDs. In which case, the answer is regulated 5 V. If you are asking this question, it is highly likely that you will wish to connect something else. And even then it was limited because an unloaded 9 V transformer-rectifier-capacitor supply would generally provide over 12 V which the regulator could barely handle. It is essentially only for demonstration use of the bare board back in the very beginning of the Arduino project when "9V" transformer-rectifier-capacitor power packs were common and this was a practical way to power a lone Arduino board for initial demonstration purposes. ![]() Here is my "stock" explanation:Ī very real danger is that the obsolete tutorials on the Arduino site and others misleadingly imply that the largely ornamental "barrel jack" and "Vin" connections to the on-board regulator allow a usable source of 5 V power. I am going to presume you are talknig about connecting 12 V to the "barrel jack" or "Vin".
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |