Yo Hal! On Thu, 02 Jun 2016 22:30:23 -0700 Hal Murray <hmur...@megapathdsl.net> wrote:
> oli...@mutability.co.uk said: > > Do you trust your power? The Pi 3 is even more picky than the Pi > > 2. > > Thanks. That could be the problem. Meter says 4.8V. I didn't get > out a scope to look for dips below that. I have heard that 4.8 is about as low as you can expect a Pi to fully function. > g...@rellim.com said: > > Everyone should have a USB V/A meter, they are cheap. Here is one > > for $6: > > Beware. Inserting a current meter will actually drop the voltage you > get. You should probably get a real meter to see if the USB meter is > showing the high side or low side of the current measuring resistor. And what do you call a 'real' meter? Any modern meter should have a really, really, small drop resistor. But, a good question. I'll open up a few of my meters to check. > > The Pi people say 2 amps is not good enough, they recommend 2.5A. > > That depends upon the stuff you plug into your Pi. With a regulated > supply, it doesn't help to have one with a higher current rating. It > might run cooler. Yes, but overkill in a power supply is always a good thing. > In theory, each USB port can ask for 500 mA. I don't know how much > the Pi will give out. Then you can plug in a HAT... Yup. The Pi has 4 ports, that is 2 A right there! Too much to think about, that is why I use the meters. > Adafruit says their wall wart style power supplies targeted at the Pi > actually set the output voltage at 5.25 to give a little more room > after the end of the cable. Good idea. And the Qualcom Quick Charge go up to 9V, and more. > > 28AWG is 0.064 ohms per foot. Double that for out and back to > > 0.128 ohms/ft of USB cable. > > 0.128 * 3 * 0.7 is 0.268 V. So if you start with 5V, you will be > under 4.8. > > Adafruit also has 6 inch cables. :) I like my Tronsmart 20AWG cables, and I keep them as short as I can. RGDS GARY --------------------------------------------------------------------------- Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 g...@rellim.com Tel:+1 541 382 8588
pgprLwped7VVE.pgp
Description: OpenPGP digital signature
_______________________________________________ devel mailing list devel@ntpsec.org http://lists.ntpsec.org/mailman/listinfo/devel