Am I going crazy?

I keep hearing people saying "you can't power a servo straight from the Arduino" or "you can't power a relay directly through the Arduino".

In my experience this just isn't true. I've triggered relays, flipped servos, and turned steppers straight from the +5V pin. One of my Unos had 30 amps fed through the VIN pin once and it still works. All three of them survived a defective prototyping shield which shorted out any Arduino it was connected to.

Am I going crazy? Are the boards I have just weirdly resilient? They are from three different manufacturers and they're all here.

'triggering' is not the same as 'powering'.
The main issues are related to the capacity of the onboard regulator of the Arduino board.

On this forum, I hear a lot of people say, "I powered it separately and it works now. Thanks!".

I've powered one puny little SG90 from an UNO. But I'm not crazy enough to use that in a project, it was just a demo.

Given your recent posting history, yes, I believe you are.

You're not the individual with the free energy powered aura detector and massager, are you?


@6v6gt Oh I don't mean triggering. Trust me.
@aarg No that's not me.
@TheMemberFormerlyKnownAsAWOL Are you holding a grudge because of my project which I decided to do?

A grudge?
You'd know if I had a grudge; you wouldn't need to ask.

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That can be very true if you supplied the Arduino board with 5V on its 5V pin and then connected some auxiliary modules to that same pin. I have no doubt that a typical header pin, given its limited length, won't melt if you push 30A through it.

But that's not what people mean if they say that you can't power s**t from an Arduino. What they mean (and usually explicitly say, if you read carefully) is: don't expect to power much from an Arduino's 5V pin when using the barrel jack to supply the Arduino as you'll be using the onboard regulator of the Arduino, and that is severely limited. Some newer Arduino boards have DC-DC converters in that position and will probably supply maybe 2A or so, but boards like UNO and Nano will start smoking like aunt Edna with her 2-packs a day habit if you try to make the poor 'Duino supply 500mA while spoon-feeding it 12V.

So you're not going crazy, per se. You're probably just misinterpreting or misreading.

The Arduino will eventually be destroyed by doing that, so have fun while you can!

You are not going crazy, just misinformed.

I don't want to know.

Makes sense. I usually power via VIN or USB. Thanks!

USB doesn't have the problem of regulator dissipation. But USB itself is current limited, and so can only support a limited number of peripheral devices. Also relays and motors create voltage transients on the power supply. There is a limit to how well those can be regulated/filtered.

Fair enough, but then perhaps your experience is extremly limited.

So what is the point here, your suggesting that UNOs can cope with 30Amps ?

When the UNO was powered with all those amps it acted up, so no. But it still works!

This doesn't make sense. You can power the UNO off the correct voltage at any amperage.
What you cannot do is draw more amperage than the pin or regulator can handle.

Did you test the servo under an active load? That is, was it actually lifting or tuning a weight or just free spinning?

Yes, the UNO acted up. I don't know why. It had a difficult time writing to serial and interacting with modules and seemed to be slower in general.

Yes the servo was loaded. Not enough to stop it, but enough that the gears screamed.

Possibly power issues, because you're not supposed to run a servo off of an Arduino directly?

So it worked, but it didn't work?

The servo and 30 amp thing were two different situations. Sorry for not making that clear.


Then it didn't work.

There's empirical data and there are product specs. Just because you were able to push the specs in one case does not change the limitations and is generally not good advice.
It's been pointed out that when a user corrects their wiring to power the servos directly, that their problems almost always go away.

I'm learning a lot here too, but I try to avoid making declarative statements like your initial one and instead I try to ask questions, like if they say not to run a servo off an Uno, then why can I do it?

JMHO though

I didn't know the battery gave that many amps until I actually took a close look at it. It's in the trash now.