Uno/Leonardo/Mega - how much current can Vin supply?

Hi!

Learned that if I feed Uno via barrel I could take power upto 1 A from Vin. Is it the same if I feed from usb? Is it the same for Leonardo? Is it the same for Mega?

Thank you

Learned that if I feed Uno via barrel I could take power up to 1 A from Vin.

Not quite, all there is between those two points is a diode which is rated at an absolute maximum of 1A. You are best restricting this to 800mA maximum, due to power dissipation issues.

Is it the same if I feed from usb?

No. The USB limit is 500mA but realistically you should be below this by at least 100mA to 200mA.

Is it the same for Leonardo?

Yes.

Is it the same for Mega?

Yes

There seems to be a misunderstanding here regarding the term "feed UNO via barrel".

The problem is not comprehending what the "Vin" or "RAW" terminal or the "barrel jack" is. The regulator on the Arduino UNO/ Nano/ Pro Mini/ Mega2560/ Leonardo/ Pro Micro has very little heatsink, so will not pass very much current (depending on the input voltage and thus, how much voltage it has to drop) before it overheats and (hopefully reversibly) shuts down. It is essentially a novelty provided in the very beginning of the Arduino project when "9V" 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 - as one suspects - you actually want to do something with the Arduino and wish to drive a number of LEDs or other similar devices, or wish to have a 5 V supply for other devices, then you simply cannot derive that from the Arduino.

Nowadays, 5 V regulated switchmode packs are arguably the most readily available in the form of "Phone chargers" and switchmode "buck" regulators are cheap on eBay so these can be fed into the USB connector or 5 V pin to provide adequate power for most applications. Unfortunately, many tutorials or "instructables" are seriously outdated or misleading and have not been updated to reflect the contemporary situation.

There seems to be a misunderstanding here regarding the term "feed UNO via barrel".

I assumed this to mean to put the voltage to the barrel connector. There is nothing to suppose it dosn't mean that. Indeed a simplton's advice would be you can take 1A out of the Vin when feeding the Uno from the barrel jack, simply because there is a 1A rated diode between the two. We both know it is not as simple as that.

If the OP wants to ask a different question to the one which his words say, it is up to him / her to use words that ask the question they want answering.