rasPi Stretch Lite install notes

Gary E. Miller gem at rellim.com
Mon Jan 8 21:42:53 UTC 2018

Yo Achim!

On Mon, 08 Jan 2018 22:28:49 +0100
Achim Gratz via devel <devel at ntpsec.org> wrote:

> > Easy, get a USB VA meter.  Good ones for $8.  You'll be amazed at
> > all the things it teachs you.    
> I have one, but how does that help me figure out the current draw
> before I buy the USB drive?

Hehehe, the problem with all Amazon purchases...

>  Besides, these meters are way too slow
> to show the dynamic peaks.

Who cares about the dynamic peak?  That is handled by the RasPi on board
capacitors.  When the capacitors can not hold up the DC any longer then
the meter sees the problem.

> > Then a 32GB SD card, in a USB adapter.  0.03A idle, 0.08 continuous
> > reading, and 0.09A continuous writing.  So not much difference.  
> It's at least a 30% difference

Sure, 30% from SD card to USB.  But compared to the 2A the RasPi
already takes, it is negligible.

> once you figure in that the adapter
> wouldn't really be needed in the first place

My SD card adapter is passive, it consumes no measureable power.

> and even more when you
> realize that it actually hangs off a SDIO-to-USB bridge on the rasPi.
> That's two bridges that do absolutaly nothing useful but burning
> power.

Yeah, and both are there, consuming power, whether you use them or not.

So it comes down to, do you have 0.10A to spare?  If you do not, you got
much bigger problems...

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin
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