Max current from onboard regulator

The EtherTen combines an Uno-equivalent Arduino-compatible board and Wiznet-based Ethernet support, along with a microSD card slot and Power-over-Ethernet support. [Product page]
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noisymime
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Max current from onboard regulator

Post by noisymime » Sat Jan 18, 2014 7:04 am

Currently I'm stripping down my letterbox setup as I want to add some more LEDs. It's an Etherten + 802.3af PoE combo currently lighting up 5x 10mm RGB LEDs, each using maybe 25mA max. This runs just fine off the etherten's 5V regulator.

What I'm wondering is what the max current I can get from the onboard 5V regulator is. By the looks of it the 802.3af regulator should give 1.5A @ 7V, does this mean I should be able to get the full 1A from the etherten's 5V regulator? Allowing say 250mA for the etherten itself, will 750mA be available for use or am I dreaming?

noisymime
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Re: Max current from onboard regulator

Post by noisymime » Sun Jan 19, 2014 5:59 am

I should've done some more reading first, the 5v regulator on the etherTen is 800mA, not 1A. So, 800mA - 250mA for the etherTen = 550mA available?

andrew
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Re: Max current from onboard regulator

Post by andrew » Sun Jan 19, 2014 9:26 pm

noisymime wrote:I should've done some more reading first, the 5v regulator on the etherTen is 800mA, not 1A. So, 800mA - 250mA for the etherTen = 550mA available?
Allow 300 mA for the EtherTen, sometimes it can burst over 270 mA.

cef
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Re: Max current from onboard regulator

Post by cef » Sun Jan 19, 2014 9:51 pm

Since the 802.3af reg does 1.5A, you could always regulate down a second 5V supply. You'd need to keep them independent, but you could (in theory) drive another ~600mA off that (leaving yourself with 100mA headroom for overhead for the regs to use - which should be a lot less but probably wise if you want it to be stable).

Note: As you're drawing lots of current, always be aware of the heat you might be putting out, especially if you're in a small enclosure.

noisymime
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Re: Max current from onboard regulator

Post by noisymime » Mon Jan 20, 2014 5:14 am

Thanks guys.
Since the 802.3af reg does 1.5A, you could always regulate down a second 5V supply. You'd need to keep them independent, but you could (in theory) drive another ~600mA off that (leaving yourself with 100mA headroom for overhead for the regs to use - which should be a lot less but probably wise if you want it to be stable).
I might have to give this a shot as 500mA is getting a little low for what I was after. If I just run half the LEDs of a separate regulator (from the 7v line on the 802.3 board) and half off the EtherTen's (with a common ground), that should be OK?

Heat should be OK as it's a nice open space.

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