What range of voltage should be expected from the Nano '5V' pin ?

i am currently getting only max. 4.2 V

from the Uno page;
5V. This pin outputs a regulated 5V from the regulator on the board

from the Nano page;
The Arduino Nano can be powered via the Mini-B USB connection, 6-20V unregulated external power supply (pin 30), or 5V regulated external power supply (pin 27).

there is no explicit mention of supplying 5V from the Nano - is this because it’s possible but not really advisable/reliable ?

i’m guessing the Uno circuitry has more components than the Nano to allow the explicit description of supply FROM the 5V pin?

i’ve read a thread that mentioned a cheap USB cable could make for a bigger voltage drop, but i’ve also tried using a 6V battery pack to the Vin pin and get quite similar results (on the ‘5V’ pin).

here are pictures of what i’ve been doing;

using USB cable;

using a 6V Battery Pack (4x AA);

i realise the 6V supply is right on the limit of the allowable unregulated supply but it (seemed) to work okay with an SD card module - now that i’m trying to work with an Ethernet module, it might be insufficient - but then, so too it seems via the USB supply !!

these are some readings i’ve made with a multimeter;

				      Voltage at
			      MEASURING point

[u]NO "ENC-y" module[/u]
using USB			    4.1 V
using 6V pack			4.3 V


[u]w/- "ENC-y" module[/u] (connected to 3V3 pin)
using USB			    3.9 V
using 6V pack			4.2 V

are these readings “normal” - given the existing layout ?

You need 6.5V or so to get the on-board regulator working properly. Stick to the recommended 7..12V input range on Vin and you won't have issues.

You cannot run the ENC28J60 from the 3.3V output of the Nano, since it
requires a minimum supply of 180mA, and the Nano can only provide 50mA
absolute max. You always have to check these things, its no good just hoping.

An external 3.3V regulator is a requirement for powering the ENC28J60.

MarkT:
An external 3.3V regulator is a requirement for powering the ENC28J60.

hahaha, whaddayaknow - keep asking questions and eventually you'll get an answer on a faintly related thread !!
thank you SO MUCH MarkT : +1 !!

i have an unanswered thread, and i'd been trawling through the copious threads on the ENC28J60 and power issue was not very commonly discussed, other than one thread saying the user was using external supply, and another also mentioned having lost connections despite it. (looking forward to those problems when i get there... {rolleye}!! )

MarkT:
You cannot run the ENC28J60 from the 3.3V output of the Nano, since it
requires a minimum supply of 180mA, and the Nano can only provide 50mA
absolute max. You always have to check these things, its no good just hoping.

i'm pretty n00by at reading the datasheet - i couldn't really find the current requirement and only saw maximum per pin amounts.

i've since got a Voltage Regulator so will be able to setup an external supply for the 3.3V but thought i'd just confirm the above for the 5V pin - i take it it's a normal reading then, what i got ? even for the USB source ?
(and the big drop from 5V is because of the cable ?)

okay, on the slightly related issue of the ENC28J60, it is now working with it's own 3.3V supply through a voltage regulator.

would still appreciate a comment on this thread itself, is the 4V reading from the 5V pin "normal" ?

i understand the ATmega328 itself can operate on less so that's why sketches still work, but is the drop of 20% on the 5V pin a sign of "something gone busted" ?

Using VUSB, the voltage present at “+5V” will be less than VUSB, by a Schottky diode drop.
And in that case, the onboard Nano regulator isn’t doing any supplying, and VUSB has a range.

The Nano can supply 5V to external circuitry, it just doesn’t have as much ability to do so as a Uno.
Uno components are spec’d for more.

As mentioned previously, to get the specified output you have to at least meet the specified input.

Cable drops occur in higher current situations involving significant lengths.
Cable resistance has a direct relationship to cable length (more length, more resistance.)

thanks for confirming my guess.

from wiki;

When current flows through a diode there is a small voltage drop across the diode terminals. A normal silicon diode has a voltage drop between 0.6–0.7 volts, while a Schottky diode voltage drop is between approximately 0.15–0.45 volts.

still another 0.55 V "unaccounted for" ?

retronet_RIMBA1ZO:
still another 0.55 V "unaccounted for" ?

Maybe there's some cold solder or poor flow. The "auto selector" diode (D1) is on the board's underside.
I zapped one once. It failed into an "ohmmic" state and didn't rectify from then on (i.e. bi-directionally resistive -- NFG).

thanks for your response, there's nobody else making any comments - i wonder whether it's such a basic issue i'm supposed to be able to find out the answer myself.

i'm quite ignorant as to electronic circuitry so i'll have to do some searching on those terms you mentioned.

i do have to ask though, what does NFG mean ?

retronet_RIMBA1ZO:
i do have to ask though, what does NFG mean ?

LOL - my ignorance reaches new levels !

and now "bi-directionally resistive" suddenly looks clearer to me !

(brief OT : what's a four-letter word with one vowel that is a verb ending in 'K' that means "intercourse" ?)

Not Functioning Good