6 Feb
2018
6 Feb
'18
9:56 a.m.
On Mon, Feb 05, 2018 at 11:06:29AM -0800, Chuck Guzis via cctalk wrote:
On 02/05/2018 10:20 AM, Mark G Thomas via cctalk
wrote:
Maximum current from a standard USB 2.0 port is 500 mA, USB 3.0 ups that to
900 mA. To really get some power via USB, you have to go all the way to
USB C connectors and PD (power delivery), where you easily get 65 W, at the
expense of quite bit of complexity on both ends of the cable.
Of course there are plenty of USB chargers that are all over the map - and
they usually just abuse USB cabling as power wiring, trying to cram 2 A or
more down it - which might not work if whoever made the cable "saved" a bit
too aggressively on the copper.
2) Many of the chips were failing to program
because my Batronix
programmer apparently requires more current than my USB port provides.
This surprised me because I have been programming chips for years
using this programmer on this computer port successfully, and this
is the first I have had the problem. Using a Anker powered USB hub solved
things. My Batronix programmer even arrived with a cheap powered hub
when I ordered it, but I never used it because it was shipped with an
incompatible wall wart, but looking at it in the box gave me the idea
that this might be the issue.
You should be aware that many "thin" Far East USB cables will not pass
the full USB 1.5A current without substantial voltage drop. I recently ran into this with a new LG portable DVD drive. It
refused to operate,
even though I'd just taken it out of the box. I replaced the "thin"
USB cable with several other "thin" ones that I had with the same
result. Finally, in desperation, I located a "thick" USB cable, plugged
the drive in, and discovered that it worked just fine.
Moral: There's a lot of garbage out there.
Is there ever, sadly. Including dangerous garbage - with the power levels
of USB C and PD, bad cables (and chargers) can actually by a serious fire
risk. Fortunately, Benson Leung is on a crusade against this:
https://thenextweb.com/insider/2015/11/05/a-google-engineer-is-reviewing-us…
Kind regards,
Alex.
--
"Opportunity is missed by most people because it is dressed in overalls and
looks like work." -- Thomas A. Edison