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CaptainBoing
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Posted: 12 January 2018 at 5:29pm | IP Logged Quote CaptainBoing

Interesting examination from Andreas Speiss on the quality of USB chords and their impact on power delivery.

As a lot of us use them to get power to our projects (at least in development) I thought I would post this as a cautionary tale - I have certainly had "ghost" problems that are eliminated when using a "proper" power connection instead of the USB lead... got one on my desk as I speak.

https://youtu.be/n70N_sBYepQ


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Grogster
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Posted: 12 January 2018 at 9:19pm | IP Logged Quote Grogster

I'm sure you mean 'Cords'.....

Power chords can certainly be provided by any hard-rock guitarist.

On the cables though, if you are wanting to power a Pi or even any of the Micromite series of boards, I highly recommend a quality cable from the likes of Jaycar. Their USB cables are to spec, and can pass a couple of amps no problem - even the long ones.

The super-duper cheap USB cables on eBay et el, and cables that come free with cheap products do tend to be more often then not, utter rubbish. One cable I cut open had four hair-thin enamelled copper wires inside. They were tiny. The USB data lines GENERALLY won't care too much so long as there is a connection present, but the power ones really DO care. A-lot in some cases. The video is quite right - it's all about voltage-drop under load. The cheap cables are like adding 1k resistors in series with the power supply, and the more current you need, the worse they are.

I can qualify my remarks by stating that more then a couple of people have had problems getting their E100 boards to work - even without an LCD connected - when trying to power them via USB and installing jumper shunt J1. It is always the USB lead. When they get a decent quality USB cable, everything magically works!

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CaptainBoing
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Posted: 12 January 2018 at 9:22pm | IP Logged Quote CaptainBoing

Grogster wrote:
I'm sure you mean 'Cords'.....

Power chords can certainly be provided by any hard-rock guitarist.



! live and learn !
"
Here's an easy trick to remember the difference. You can remember that chord deals with musical notes that are in harmony. Harmony and chord both have an H in them. Cord refers to a rope, both of which are four letter words.
"

cheers grogs
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Grogster
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Posted: 12 January 2018 at 9:24pm | IP Logged Quote Grogster

No offence. I was just getting the boot in while I could.

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CaptainBoing
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Posted: 12 January 2018 at 9:28pm | IP Logged Quote CaptainBoing

... and none taken, chubby

I always leave my ego at the door and happy to be shown I have something wrong and will (in the absence of any rebuttal) modify my thinking accordingly in the interest of personal advancement...



Edited by CaptainBoing on 12 January 2018 at 10:04pm
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hitsware
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Posted: 13 January 2018 at 1:17am | IP Logged Quote hitsware

I have found both the length and ' quality ' ????
of USB wires to my RPis affects how often
and if the low voltage indicators come on .....
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Tinine
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Posted: 15 January 2018 at 1:03pm | IP Logged Quote Tinine

I have been through a lot of junk cables but having great results

with: https://www.juicebitz.co.uk/

Heavier conductors and connectors that have a nice, secure click.
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VK2MCT
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Posted: 16 January 2018 at 8:29am | IP Logged Quote VK2MCT

I was once troubleshooting a cheap flatbed scanner.
It got power from the USB cable, rather than having a separate power supply.
Used close to 1 amp up the USB as I recall.
After lots of wasted hours, it turned out to be a stuffed cable.
John.
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Boppa
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Posted: 16 January 2018 at 11:13am | IP Logged Quote Boppa

Its not surprising, I have a usb here I cut into pieces for a project and the wires inside are only a mm in diameter, and when you look at the insulation, its thicker than the copper inside- it would be well under 0.5mm.
I mentioned in another thread that I am also suspicious of the microB usb connections after testing several old (1 yr old plus)leads that were still sealed in their packages, never used and 3 of the 4 tested had failed connections in the microB plug end (all different brands)
I suspect they have a crimp style connection that corrodes internally, only because of the high failure rate of unused cables that had been in storage for a while (they were in a box of cables in my back bedroom so no real reason for failure apart from age)
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