5V vs VCC Vs Vin?

Hi!
What's the difference between 5V vs VCC Vs Vin?
If I want to power the arduino with a 3.7V lipo, where do I connect it to?
Where does regulated 5V power go?
Which pin do I use for what?
I'm making my own arduino compatible but the atmega328 had only VCC pins and no 5V or Vin so I became really confused. Can someone give me a really specific explanation of those 3 pins?

Thanks!

PocketHarambe101:
Hi!
What's the difference between 5V vs VCC Vs Vin?
If I want to power the arduino with a 3.7V lipo, where do I connect it to?
Where does regulated 5V power go?
Which pin do I use for what?
I'm making my own arduino compatible but the atmega328 had only VCC pins and no 5V or Vin so I became really confused. Can someone give me a really specific explanation of those 3 pins?

Thanks!

If you're unsure about this topic, perhaps building your own atmega328 is getting a bit ahead of yourself. VCC is only for the chip and requires 5V. Vin (nominally 7-12V) and 5V (must be 5V in, or can be 5V out) are extra elements on various Arduino boards.

Cheers!
Dirk

The question suggests you have never heard of a data sheet and/or never read one.

Oh, I get it!
So, the VCC accepts unregulated input and the 5V pins needs regulated 5V input(or can be set to output).
So if I connect a 7805 voltage regulator to my atmega328, I can make it work.

Maybe making my own board is getting ahead of myself, but I already finished almost everything and after a few revisions I will make a few pcbs.

The question suggests you have never heard of a data sheet and/or never read one.

I have, but all the pinout diagrams and datasheets don't tell me(or maybe i'm just too lazy to go over all of them)

1 Like

Vcc on an IC is NOT unregulated. It needs to be what it is designed for, whether that is 5V, 3V3, or lower. Decoupling capacitors are used to help ensure a clean supply voltage, whether that is from USB or a LDO regulator.

You should learn the difference between board specs and IC specs. There are datasheets for both.

All you have to do is open the 660 page datasheet with Adobe reader and select chapter 1.1 Pin Descriptionss under which the first item is 1.1.1 Vcc, which is described as “Digital Supply Voltage”,
which , can in no way be confused with “Unregulated Voltage”

Vcc PIN DESCRIPTION.jpg

DATASHEET

raschemmel:
All you have to do is open the 660 page datasheet …]

This of course was an Atmel datasheet, not an Arduino datasheet. People still land on this page and there are no answers yet.

Boards generally have an onboard voltage regulator. Some of which can struggle above 150mA, especially for Nanos and Tinys. If you have a suitable supply, this can be bypassed.

5V is normally OUT, used for things like I2C device power, but you can hook this up to a lower voltage battery, batteries will not have ripple or RF noise, but they may droop. Bear in mind anything relying upon regulated 5V as a “reference” will scale to your battery voltage.

Vin may or may not be regulated, but should be above 5v for further regulation to 5V (nominally)

Vin should generally be < 12V, probably no higher than 15V, depending upon the regulator and the upstream capacitor limits. The odd LM7805 regulator can cope with 35V, but the capacitor maybe only 16V. The higher the voltage the less efficient the regulation will be.

Vcc is the DIP package supply, it should be 5V, whatever the source, but boards might range from 2.7V to 5.5V depending upon design and that datasheet.

You should be aware of “Brown Out Detection” and disable it, or set it below your battery vor a oltage.
Your results will be arguably better with a “Branded” board.

For a 3.7v LiPo I would strongly recommend a 3.3V Nano type design, through the onboard regulator with a switch to prevent the battery from draining through the regulator when the board is quiescent.

2 Likes

What's the difference between 5V vs VCC Vs Vin?

I was wondering the same thing actually after got my second board yesturday. so i googled it and found this post which contained the answer (Thanks btw :slight_smile: )

Also when someone stops you on the street to ask for directions, Do you tell em to go get a map? Or perhaps you say to them that they are getting ahead of themselves? or suggest that they have never heard of street-signs?

I see no reason to be a condescending jerk nor doubt the skill level of the person who is asking the question. especially when there seems to be a confusion around Arduino and Amtel datasheets.

8 Likes

CryptFS:
I see no reason to be a condescending jerk nor doubt the skill level of the person who is asking the question. especially when there seems to be a confusion around Arduino and Amtel datasheets.

Whoah! A bit of a 'tude there! :astonished:

Perhaps you need to read the reference! :roll_eyes:

Hi,
Have you looked at the schematic of a Arduino UNO?

Tom... :slight_smile:

Hand holding is not our speciality. Generally a lot of questions can be found with Google search or checking datasheet and asking here is fine but one shouldn't expect us to spell out every single thing. Like school teacher, we can point direction and guide them but we generally won't give out all the answers. No one here gets paid to help.

I apologize if i stepped out of the line, yes i know the rules of tech forums and stupid lazy questions, ive spent years browsing them for my own research instead of posting questions like this, but i never understood why people who dont want their valuable time wasted with stupid questions would gladly waste it to jerk someone around instead? ironically they end up wasting time of those who silently choose not to waste theirs by googling a stupid question. so they can find a stupid answer that sheds light on why and how their micro-controller might have got bricked.

Dont need to answer this btw, ... read the rules, Ignore me

1 Like

Did we ever get to the answer? @CryptFS - I agree with you. If there was a Google answer, shouldn't it be on this forum?

toddsantoro:
Did we ever get to the answer? @CryptFS - I agree with you. If there was a Google answer, shouldn't it be on this forum?

it is !!

i searched for this two days ago and found this.

1 Like

By convention Vcc these days means the positive logic supply rail (*)
5V is a voltage, not a signal or supply name. Many logic devices have Vcc = 5V, many do not.
Vin is as documented in the description of the board the input to the on-board regulator.

So you can treat Vcc or Vdd as meaning "logic supply" as opposed to analog or motor supply, for instance.

(*) Originally Vcc = "voltage collector collector", Vee = "voltage emitter emitter",
Vss = "voltage source source", Vdd = "voltage drain drain", were used for various TTL and
pMOS and nMOS families.
Eventually as a the great variety of devices slimmed down to just TTL and CMOS 5V, Vcc was
used commonly for all logic (although it makes no sense for CMOS where both rails are FET
sources!). Vdd is also used.

For the record, these days, this page is the second result on google for “difference VCC 5V arduino”. I came here having bought an arduino bundle, the instructions for which don’t walk you through the electronics before throwing you in at the deep end with circuitry.

To a beginner who is keen to learn this forum seems rather unwelcoming.

Thank you mckenzm. I have much to research before I fully answer your question but I now have a lot more to go on than the datasheet provided me. The datasheet isnt very helpful because I needed to know what these terms mean in practical terms like “this is the pin to which you would connect a battery etc”.

Thank you all for your helpful onward leads (no pun itended :wink: )

MarkT:
(*) Originally Vcc = "voltage collector collector", Vee = "voltage emitter emitter",
Vss = "voltage source source", Vdd = "voltage drain drain", were used for various TTL and
pMOS and nMOS families.
Eventually as a the great variety of devices slimmed down to just TTL and CMOS 5V, Vcc was
used commonly for all logic (although it makes no sense for CMOS where both rails are FET
sources!). Vdd is also used.

You made me dizzy there.