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Topic: Maximum current draw on 5v and vin pins? (Read 30685 times) previous topic - next topic


Hello! I'm new to this community and hardware in general, I come from a software background. I am working on a small introductory project, essentially attempting to interface a number of components together using an Uno. I've haven't been able to find any information regarding the maximum current I can safely draw off the 5v and vin pins. The data pins are rated at 40 mA and the 3.3v pin is 50 mA. I believe there's a soft fuse in the voltage regulator which blows at 500 mA to avoid pulling too much from a usb port. Am I safe below 500 mA or is there more to consider? If I do end up needing to power other components separately due to current limitations, is something like this the correct solution: http://www.dimensionengineering.com/DE-SW050.htm ? Any advice would be much appreciated!


Jan 29, 2011, 12:44 am Last Edit: Jan 29, 2011, 12:49 am by retrolefty Reason: 1
Well here are the rules for +5vdc usage for output pin current ratings, total processor chip rating, and total board current ratings.

Output pins:     Recommended continuous current, 20ma. Absolute maximum above which will damage pin/chip 40ma (use 20ma recommendation)

Total chip Vcc current (all output pins total and chip overhead): 200ma., i.e. 10 output pin driving 10 leds @ 20 ma is max for whole chip.

Total +5vdc current available for on-board and external use:

If USB powered: 500ma max limited by on-board thermofuse and USB standards.

If powered via on-board +5vdc voltage regulator driven by external power socket (Input Voltage (recommended) 7-12V ) :
not specified, but don't plan on using more then 500ma max.


The data pins are rated at 40 mA

That's maximum, not recommended as the norm, as retro says, stick to around 20mA.

If I do end up needing to power other components separately due to current limitations,

Use whatever is providing your VIN, regulate that down to whatever the other circuitry needs an dmake sure everything has a common GND.

is something like this the correct solution

I haven't used them but they seem pretty good (another similar thing is the TRACO TSR1 series). You can of course use any regulator, you just need to look at the circuit you want to power and select something suitable.

Rob Gray aka the GRAYnomad www.robgray.com


That switching regulator is a nice device due to it's much better efficiency over linear voltage regulators.

However you might want to take a gander at a switching regulator I have ordered (but not received) as it's cheaper, has a higher current range and is adjustable in output voltage. It is however perhaps a little larger in size:




VIN decoder

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