Voltage Drop

I bought a 12VDC converter to power an Elegoo Nano but my multimeter measured 12.3V. The Nano also seems to be making a high pitch noise, which I assume is the voltage regulator straining. Would I be able to put a standard .25W 330Ohm resistor in between the converter and the ground(?) and would that help?

A true Arduino Nano would be fine with a 12.3Vdc input (the LM1117-5.0 LDO is good to up to 20V max.) If your Elegoo thingy is a direct copy of the Arduino down to the partnumber, it should be fine.

The true Nano doesn't use a switcher (it's a linear.) Unless the Elegoo is using a switcher I wouldn't expect to hear anything. Cheap 12V AC/DC bricks often have crappy regulation and tons of ripple. Consider getting a better supply.

Not very wise to power a Nano (clone or official) from 12volt. The onboard 5volt regulator has very little heatsink area, and >=50mA drawn from any pin could already fry the board. Better to power the Nano with a 5volt cellphone charger, connected to the USB socket. Leo..

I ended Googling it. fI'll just use a voltage divider and switch to a grounded plug. I hate wall warts.

pi_thyme: fI'll just use a voltage divider and switch to a grounded plug. I hate wall warts.

Get over it. A modern switching 5volt cellphone power supply is the most efficient way of powering an Arduino. Voltage dividers (with resistors) are for signals, not for powering devices. Leo..

pi_thyme:
I ended Googling it. fI’ll just use a voltage divider and switch to a grounded plug. I hate wall warts.

Yeah, well the Internet is full of really bad advice. Like how a grounded plug and a voltage divider will help prevent overheating a linear voltage regulator. Just another unexplained mystery of the universe. But, hey, it’s free.

The high-pitched noise is not coming from the nano - it's coming from the switching power supply. Switchers often make a high-pitched whine noise, particularly at the extremes of their output current range (some squeak when in discontinuous mode at very low current, and almost all will start to squeal if you push them to their limits). The cheaper the power supply, the more likely it is to be noisy.

12v will work as input if it's got a full-sized 1117-series linear reg, as long as you're not drawing that much current from it - but it's better to use lower voltage as input to the linear regulator (7~9v would be good). Using a 5v switching power supply is of course the best way - 5v "phone chargers" are so cheap and so readily available that it is hard to justify using anything else.