VIN pin

I have a 12 volt power supply. From reading, the VIN pin can take a 6v-12v coming in. I would take the pos+ from the PSU put into VIN and neg- from PSU and plug that into GND. I was told this is the best way to power up the Arduino, because the VIN is regulated.

12V is the upper limit that you should apply to Vin. If you try to draw much current from the digital output pins, or the 5V output, the regulator will overheat. A couple of LEDs are OK, but not much more.

It is better to use 7-9V for Vin.

The best way is to use a USB wall adapter to power it, because no onboard regulator is used, and any device that uses 5V obtains it almost directly from the adapter. Such adapters are in fact, regulated power supplies.

Does your PSU have multiple voltages, +5, +12, -12 etc?

647chang:
I was told this is the best way to power up the Arduino, because the VIN is regulated.

You were told wrong!

A very real danger is that the obsolete tutorials on the Arduino site and others misleadingly imply that the largely ornamental "barrel jack" and "Vin" connections to the on-board regulator allow a usable source of 5 V power. This is absolutely not the case. It is essentially only for demonstration use of the bare board back in the very beginning of the Arduino project when "9V" transformer-rectifier-capacitor power packs were common and this was a practical way to power a lone Arduino board for initial demonstration purposes. And even then it was limited because an unloaded 9 V transformer-rectifier-capacitor supply would generally provide over 12 V which the regulator could barely handle.

If you are asking this question, it is highly likely that you will wish to connect something else. In which case, the answer is regulated 5 V.

This is because the on-board regulator is essentially capable of powering only the microcontroller itself and no more than a couple of indicator LEDs. The on-board regulator might be able to power a few other things if it had a heatsink, but on the (older) Arduinos, it does not.

Powering via the "barrel jack" or "Vin" connections is asking for trouble. The "5V" pin is not by any means an output pin, if anything a "reference" pin but most certainly the preferred pin to which to supply a regulated 5 V.

A practical power supply for the Nano (or UNO, Pro Mini, Leonardo etc.) is a "phone charger" with a USB output connector for 5 V, generally up to a couple of Amps though you can not feed more than 500 mA through the USB connection.

If you want to power it from 12 V or a car system, you need a 5 V switchmode "buck" regulator to supply the 5 V.

If USB plug into a 5v is number one. What would be your 2nd choice. 5v going to 5v pin, or 12v going to VIN. Which one of those 2 is safer?

Powering through Vin or the power jack means that the Arduino and all peripherals that are on the 5V rail are powered by the onboard 5V regulator. The on board 5V regulator is not heat sinked so will supply limited current before it overheats and shuts down. The recommend max power dissipation for the regulator is 1 Watt. With 12V into the regulator the max current is about 140 mA (1W / (12V - 5V)). The Arduino uses around 50ma of that leaving less than 90mA (max) for everything else. I would use a buck converter to drop the 12V to 5V and connect that to the 5V on the Arduino, bypassing the, weak, 5V regulator.

If you can supply 5V to the Arduino 5V pin, from an external power supply, then there is no inherent limit on the external load except what the supply can safely produce. Then, the only practical limits on Arduino power are related to the current loads that you place on the I/O pins. Such a supply is not limited like a USB is. Hence the absolute best way is a good external 5V supply.

For example, you could have a 100 Amp 5V supply running a whole lot of RGB strips, and the Arduino. The example 65 Amps of power going to the strips would have no effect on the Arduino, which only has to drive a few digital I/O ports in the direction of the strips, so possibly about 30mA total for the Arduino. A lot of that power goes to the little onboard LED. :slight_smile:

But you have to watch out, that the 5V is regulated, and noise free.

Its all very interesting reading some of these comments.

Firstly the OP hasn't said which board he is using.I have a Nano and an UNO which both use an AMS1117-5.0. This regulator is rated at 1A which should be more than enough to power most small projects.

If the OP could provide more info on what board he is using and what he wants to do it would be much easier to answer than to give him false info.

PS. I use AMS1117-5.0 chips (or equivalent) in most of my project boards and never had a problem. If I need more grunt I will use relays controlled though a DS2003 or similar.

windoze_killa:
Firstly the OP hasn't said which board he is using.I have a Nano and an UNO which both use an AMS1117-5.0. This regulator is rated at 1A which should be more than enough to power most small projects.

I think you are not taking into account the thermal resistance to ambient specifications of the regulator. The heat sinking on that is extremely minimal, it will severely de-rate the maximum safe output current.

It will work up to 125 degrees C, but do you really want any part of your board to run that hot?

Also, some projects run in a box. The less heat the better in that case, because the heat is somewhat trapped. Then the ambient goes up, and the danger gets even worse.

Firstly the OP hasn't said which board he is using

Not only that, the OP hasn't answered the posted question of what power supply he is using. Also hasn't volunteered what the load device(s) are...

I agree totally.

But as we have both said, until the OP tells us what the missing info is the easy answer will be, "my 12V 60A PSU". Power supply will not even flinch as it melts the micro.

aarg:
Not only that, the OP hasn't answered the posted question of what power supply he is using. Also hasn't volunteered what the load device(s) are...

OP left the chat...

"What he said..."

windoze_killa:
I have a Nano and an UNO which both use an AMS1117-5.0. This regulator is rated at 1A which should be more than enough to power most small projects.

If and only if it was attached to a genuine heatsink, which it is not. That - as always - is my point.

TheUNOGuy:
OP left the chat...

That is a bit premature.

We do have to allow that people eat, sleep and go to the toilet. Some of us work. :astonished: I generally give at least 24 hours since last (or only) posting before signalling demise of a thread. :roll_eyes:

The Arduino board I am using is the Arduino Mega 2560 R3 ATmega2560-16AU

The power supply Im using is Alitove DC 12v 10A 120W

Im using the PSU to supply 12v to my 16 channel relay board and to drive 16x peristaltic pumps.

The pump will most likely be ran one at a time. I don't know the specs for them yet, and can't find anything about them. I still waiting for them to arrive. Also the relay board has a 5v coming out of it. Im planning on supplying the 5v on the ardunio from the relay board. This should be fine if it don't supply any other power coming in (barrel jack, usb)?

Pump 170-460mL/min

Arduino Board

PSU

16 channel relay board

Also the relay board has a 5v coming out of it.

How do you know this? The product page you linked has no information regarding such.

Motors inject voltage spikes into motor power supplies, so strictly avoid applying the motor power supply voltage to Vin. Instead, use a 5V step down regulator and apply 5V to the 5V pin.

This is what I have found online

Remarkably little information and rather unprofessional! If this were my project, I would write to the uctronix and ask them

  1. How much current can the on board 5V regulator safely supply?

  2. How much current must each Arduino output sink to activate a relay?

jremington:
Remarkably little information and rather unprofessional! If this were my project, I would write to the uctronix and ask them

  1. How much current can the on board 5V regulator safely supply?

  2. How much current must each Arduino output sink to activate a relay?

Trust me youre not the first person to say they have a lack of info. All the 16 channel relay seems to be really bad with their info.

This is the third thread for that project,
and most of the answers here are already given in the other cross-posts.

Reported.
Leo..