I'm using an LED driver, which requires a few data lines and a good amount of power (~320mA at absolute full power, but in general maxes out at around 150-200mA for my purposes). The power supply I want to use uses a micro-usb cable, so I could just plug it directly into my MoteinoLeo and have the leo power the LED driver.
I'm considering powering the driver by turning on a bunch of digital pins and running them all to the power input of the driver, while also turning off a bunch of digital pins and running them to the ground. I assume that the internal resistances are close enough that I would get roughly even current draw on all pins, allowing me to stay under the 30mA limit for each pin.
Two questions:
1) Would this work?
and 2) Is there some unlisted maximum current for the entire board that I would be exceeding?
Hm, sounds to me like you might push the limit. The onboard regulator can give a max of 250mA according to the datasheet. However I would not go so close to that. Remember the micro is not really meant to be used as a power supply, but rather a switching source. I would use transistors/mosfets to switch a lot of power. I mean look around the internet, all the LED drivers are using some kind of switching devices or have dedicated power for the bulk power that is needed.
I would imagine at 200mA the little regulator will get pretty hot too. So I think overall I would not recommend pulling that much current.
I was just messing around with my board and realized that I can draw power from the Vin pin.
Is this a direct feed from the micro-usb, and how much current can it handle? It doesn't seem to go through the regulator, which is fine for my purposes. I really just don't want to have to get a breakout for my power supply.
Hi,
Standard USB are 5V and 0.5 A. There are special "high power" usb ports for PC which are used to charge devices like iPad or similar and gives 1A. If you use a AC to DC converter, there are up to 1.5-2 A. If you use the Vin pin I guess you can use the total current minus the current consumed by the micro+RFMXX.
Jaime was pretty spot on.
VIN is whatever you feed from the external source. So for a Leo it would be your USB, which should handle up to 500mA.
If you're trying to push the limit and see how close you can get to the edge without falling over, then I would advise to look for alternative solutions to squeezing power from your USB ports :), like .. an external power supply.
These chips have a spec which I don't doubt they will meet, but in day to day operations you never want to feed your power hungry devices through the chip itself or from a USB.