Does anyone know what a rated output current may be, precisely, for the 5V pin of the Uno? (Using a 9-12 VDC 1 Amp power supply input, not USB)
I can find no specs on what appears to be a On technology RXA117-5 voltage regulator on the Uno.
No 5V currents are mentioned on the data sheet, while the 3.3 volt output is listed at 50ma. Strange omission.
RWA117-5
The schematic indicates the part is number NCP1117ST50T3G.
Ashton:
Does anyone know what a rated output current may be, precisely, for the 5V pin of the Uno? (Using a 9-12 VDC 1 Amp power supply input, not USB)
I believe the Uno uses a 1A regulator. Also, there is a 1A diode in series with the barrel jack. However, you're more likely to be limited by power dissipation in the regulator. Say you feed 12V into the barrel jack and take 1A total from the regulator. Then the regulator has to drop (12 - 0.7 - 5) = 6.3V, causing to to dissipate (6.3V * 1A) = 6.3W. This will probably cause it to go into thermal shutdown after a few seconds.
Great, thanks.
I plan to use the 5V to charge a battery in another device for a couple hours on a certain day of each week. The current will be ~30-40ma.
So I'll be sure to use the 9V power supply too.
Thanks
30 to 40mA should be no problem. The total current would be only 90mA (including 50mA for the Arduino itself), so even with a 12V supply, the power dissipation would be only about 0.6W, which the regulator will handle.
(6.3V * 1A) = 6.3W. This will probably cause it to go into thermal shutdown after a few seconds.
6.3W into a package that can disspate about 0.5W average. This would be an interesting
test I should try one of these days. Will it really go into thermal shutdown, or just pop like
a popcorn kernel? What do you think, dc?
oric_dan:
(6.3V * 1A) = 6.3W. This will probably cause it to go into thermal shutdown after a few seconds.
6.3W into a package that can disspate about 0.5W average. This would be an interesting
test I should try one of these days. Will it really go into thermal shutdown, or just pop like
a popcorn kernel? What do you think, dc?
You doubt the datasheet bullet point features of overcurrent and overheat automatic shutdown protection?
Lefty
That doesn't answer the conjecture I posed. Thermal shutdown is some sort of internal
process, and takes a certain amount of time, and may be overshadowed by other
circumstances. To give an example, sometimes things burn up before circuit breakers act.
Here is a picture of the 120VAC outlet which was feeding the microwave oven [installed
by the previous owner, I luckily smelled the "smoke" in time],
Sure, but datasheet specs are under ideal conditions and don't take into account the heatsinking, etc., of real life devices.
The only true test is to put your finger on it. If it burns, you're overloading it.
Why are you responding to my post? I don't have a skin in this game. I was merely trying to get @Ashton to the correct datasheet.
I don't have a skin in this game.
He just doesn't want you to burn your finger, ;-).
Huh. It seems to have worked. No burns!
