Arduino Nano- VIN vs USB for desk project

Sorry - it was tricky to work out where to post this....

I'm making a project for my work desk (a binary clock). It uses a nano, is quite low power, runs the nano, a DS3231 board, 3 shift registers and a handful of LEDs (0.5mA each max).
Past projects have all been more remote, and I've powered with batteries into VIN. This one will sit on a work desk, so I have the choice - VIN or USB.
Is there a better electronic choice? For convenience, USB wins, for supply of adaptors and the socket is right there too. If there are suitable advantages to VIN I'll consider it.... are there any??
Thanks for any advice.....

VIN requires at least 7V and wastes power in the conversion to 5V

Use USB or a 5V stabilised supply to 5V

For convenience USB wins hands down

The point is this:

You have an ATmega328 microprocessor chip.

It is intended to run on 5 V. That is the design voltage, at least to use a 16 MHz clock which is what the Nano has. To use USB, it also has a USB interface chip which is - generally - designed to run on the USB voltage which is 5 V. That is 5 V OK? :astonished:

I repeat my "stock" explanation to this question every time. The "Vin" - or "Barrel jack" on a UNO - is nothing more than a legacy "novelty" from the times ten or twenty years ago when 5 V switchmode power supplies were not common as they now are. It allowed you to use unregulated 9 V "plug packs" (US: "Wall warts") which were the common supply for computer "phone" modems and ADSL boxes which contained heat-sinked 7805 regulators. But the regulator on a tiny Nano or even the UNO board has minimal heat-sinking and is only suitable for simple demonstrations of the basic board and a few LEDs.

For protection, there is a diode between the USB connector and the 5 V supply line (which is also the "5V" pin) in the Nano, so plugging 5 V power into the USB jack loses a significant part of a Volt before it gets to the 5 V line. According to the original circuit, this would be a SS1P3L with only 350 mV drop and capable of passing one Amp, but depending on what clone you have, this may be quite different.

So you can simply forget the on-board regulator and "Vin" and when you have a nice regulated supply of 5 V - generally from a USB "phone charger" or switchmode "buck" regulator - you want to convey it to where it is actually required - the "5V" pin and your other modules. :grinning:

Thanks guys, I was checking there wasn't some other reason I should consider the Vin pin. I'm glad there isn't! :slight_smile:

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