Unique Vin pin usage.

Bill of materials:

components

Authentic Arduino brand NANO (current model)
5v @ 200ma BLDC fan
5v @ 500ma ultrasonic humidifier
multi-voltage regulated 2 amp wall pack (set to 12v)
DHT22 (5v supply requirement)
Relay (5v supply requirement)

Pin outs

D4, DHT22
D5, Relay

** Project Scope**

Humidification controller for incubator. Operates a 5v fan and humidifier when programmed conditions are met.

########## PROBLEM ###########

Ok so I have basically everything running from 5 volt except for the nano itself which will be supplied a regulated 12 volt.

I have read that the Vin pin is powered from before the onboard regulator. Is my source correct? if not please point me in the right direction documentation wise.

If Vin pin is powered from before the regulator. Would that mean I have the regulated 12 volt supply coming through that pin from which I can run a LM2596 buck converter to give me the 5v voltage and current draw I would need to run the fan and the humidifier? (of which I think may be too much for the nano natively)

Basically I do not want to have a second power source or to muck around with more wiring than I have to.

What do you guys think?

Your wording is confusing.

You can power the Nano by connecting externally regulated 12v to the Vin pin, 7 to 9v would be better.

You can connect the 12v supply to two 5v buck converters, one for the load and one for the Nano.

The 5v going to the Nano would connect to the Nano 5v (Vcc) pin.

Slant_Eng:
Authentic Arduino brand NANO (current model)

I think there are currently seven official Nanos, and some of them are very different.

A common 5volt 16Mhz Nano does not like to be powered by 12volt.
It can be powered with 5volt on the 5volt pin.
Why not use a regulated 5volt supply (cellphone charger) for all your items.

I hope you mean a relay module, not just a relay.
We can advice you better if you post links to the parts, and/or a picture of the setup.
Read the "how to post" sticky that you can find on top of every main page.
Leo..

Can a moderator please delete my post. I am wasting time asking questions here...

Why that.
We also will be wasting out time if you don't provide us with the right hardware details.

So let's assume you don't have a member of the new Nano family, but a standard/cheap Nano.
Then yes, the V-in pin is the input of the onboard 5volt regulator, and it needs 6-9volt to make a stable 5volt.
But you can also power the Nano directly with 5volt on the 5volt pin, bypasssing that regulator.
Leo..

I use larryd suggestion all the time. The reason is I have a much better power on the Arduino, it has filtering, has noise rejection etc. The Arduinos work much better in harsh environments that way because of the additional filtering. However I also have another rule I never use the arduino as a power supply. This method also gives a much superior Vref when using the analog to digital converters and there is no bumps from load switching. My standard configuration is a SEPIC converter from the main DC power for the Arduino and another for the accessories that do not run on the main DC power, which is either 12 VDC or 24 VDC. This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil