Quality USB A TO B cables ?

[exxos]

Is anyone know any actual quality USB cables ?

Some of the printers only seem to use 20cm cables as others " cause issues". I think in part it is because of the power capability of them and the voltage drops across them ( same problems with phone charger cables).

I keep looking and cannot really find any cables with any sort of "meat" in them. They all seem really thin and generally "un-branded". Saying that I have a Belkin USB cable where I cannot even get the printer to connect with it. It does look thicker than most as well :roll:

I hope Linus will review USB cables at some point...

[exxos]

Found these

"Supra Cables USB 2.0 Cable 2 M"

1.JPG

:shrug:

[Steve]

I'd go for either of these... not sure if it's the same Belkin as you already have.

https://www.ebay.co.uk/itm/124969407956?


https://www.ebay.co.uk/itm/174826943295?

[exxos]

I'd go for either of these... not sure if it's the same Belkin as you already have.

Looks similar, but mine has orange on it.

[exxos]

I did some quick tests on 2 cables.

Belkin 2M cable

Testing the left pin, which I believe is the power ( same distance on the pin above)

IMG_7152.JPG

IMG_7153.JPG

Then a right-hand pin which I believe is data.

IMG_7154.JPG

IMG_7155.JPG

Is around 0.768ohms on the power and 0.672 on the data. So if we round up to 0.8 ohms, based on 5V supply, 0.5amps, we get about 0.374V drop. So 5V - 0.374 = 4.626volts. Not great by far.


Next up a Startech cable 1M.

IMG_7148.JPG

IMG_7149.JPG

IMG_7150.JPG

IMG_7151.JPG

Power 0.107 ohms, Data 0.207ohms. So if we take the power resistance of 0.1ohms 5V 0.5A we get about 0.05V drop, much better! even if we doubled the length of this cable was still only have 0.1V drop.

The Startech cable works much better, But I'm having to run through a 1M extension cable. The Belkin cable I cannot even get to connect to my printer. This cable measures 0.340R & 0.250R

At this point I am assuming the voltage drop because of the issues. *However*, my next test I'm going to connect my scope to the actual data line and see what kind of noise there is...

IMG_7156.JPG

Not too shabby I guess..

Looking around the net...



https://www.yoctopuce.com/EN/article/us ... ze-matters

Seems I am not the only person running into such problems.. So the hunt is on for a better cable..

[exxos]

It is pretty bizarre how terrible this information is listed.

The startech cable simply says..

Wire Gauge24/28 AWG

A different cables states..

28AWG(7/0.127TC)*1P+24AWG(7/0.2TC)*2C+AEB(65%AL)

Has been some years inside dealt with cables but it used to be quoted like, the gauge of the wire and the number of strands. I assume "0.2" square millimetre area of 24AWG, where it has seven strands.

However when I plug some basic figures into this site https://www.rapidtables.com/calc/wire/v ... lator.html

Capture.JPG

This is just for *one* 24awg strand. Now if the startech cable was a single 24awg strand, and I get the resistance of 0.1ohms, it pretty much matches what that site says.. But seriously.. *ONE* strand of 24AWG ?!

It could however mean 7 strands of whatever "0.2TC" is, making up the total area of 24AWG. It could may well be true as such tables use tiny thin wire and only a few strands. The technically will be more like 30AWG of 7 strands giving a " total area" equivalent of a single strand of 24AWG.

I think I will just have to buy that cable and actually measure it :roll:

[exxos]

New cables came.

RS PRO Male USB A to Male USB B USB Cable, 2m, USB 2.0
https://uk.rs-online.com/web/p/usb-cables/2012476

IMG_7158.JPG

IMG_7159.JPG

0.273R on the power. Cannot be bothered to look into this any further.



Roline Male USB A to Male USB B USB Cable, 1.8m, USB 2.0
https://uk.rs-online.com/web/p/usb-cables/8158447

IMG_7160.JPG

IMG_7161.JPG

0.168R. Even though this cable is 2 m, if we compared to the currently best startec cable at 1M, (0.168 / 2) = 0.084R so the Roline seems to be the best overall so far.

Still trying to understand the specification for the cable..

ro.JPG

2m.JPG

Calculator quotes 0.336R, While the measurement is actually 0.168. If we actually double that resistance we would get calculated figure (0.168 x 2 = 0.336).

The only thing which could possibly make senses the"*2c" on the end of the line which may mean x2 conductors of 24AWG. it is the only sort of calculation where it would add up which I can see.

I guess it will be interesting to find a cable which says "*3C" on the end for 24AWG wire.. Someone is willing to wade through the datasheet is to find one then I can try..

[bigbloke]

Still trying to understand the specification for the cable..


ro.JPG

Hi Exxos,

That cable spec reads
UL-2725 --- Cable drawing specification composed of:
28AWG(7/0.127 T.C)*1P --- means 1P(air) made with 28AWG cables of 7 cores each of 0.127mm2 cable with T(wisted).C(ores) These will be the data pair on USB
+24AWG(7/0.203 T.C)*2C --- means 2C(onductors) made with 24AWG cables of 7 cores each of 0.203mm2 cable with T(wisted).C(ores) These will be the +5V and 0V/GND red and black wires
+AL/MY --- Aluminium Mylar film plasticy screen foil
+DRAIN WIRE --- not sure on a USB cable (unless they mean for the braid to connect to the USB shells
+65% BRAID --- overall screening with 65% wire to space ratio
rest means PVC sleeve and black colour and finished O(utside)D(iameter) of 4.7mm

A very rigorously specified cable!

Hope that helps your understanding. Measuring resistance of cable really is difficult to do even with your nice fancy 4 terminal meter. It only needs a "poor" connection at either end to mess up the readings. By which I don't imply you are doing it wrong, but a slight tarnish or not tight clip can make a world of difference to values read.

I have never studied USB cables in this detail, so what you are finding is interesting to me. Thanks for posting

[exxos]

28AWG(7/0.127 T.C)*1P --- means 1P(air) made with 28AWG cables of 7 cores each of 0.127mm2 cable with T(wisted).C(ores) These will be the data pair on USB
+24AWG(7/0.203 T.C)*2C --- means 2C(onductors) made with 24AWG cables of 7 cores each of 0.203mm2 cable with T(wisted).C(ores) These will be the

Thanks, it is sort of what I was getting at previously, but this is a good explanation. :thumbup:

Measuring resistance of cable really is difficult to do even with your nice fancy 4 terminal meter. It only needs a "poor" connection at either end to mess up the readings. By which I don't imply you are doing it wrong, but a slight tarnish or not tight clip can make a world of difference to values read.

Indeed the setup is not ideal. But if there is a bad connection the resistance jumps all over the place. I do take several readings to make sure I'm getting as good as figures as possible.

I have never studied USB cables in this detail, so what you are finding is interesting to me. Thanks for posting

:cheers:

[bigbloke]

With reference to your calculator snapshot and questions: The cable calculator resistance would be the equivalent resistance when passing 500mA at 5V. Your meter (probably) isn't doing that exact test, so that is why you see a lower resistance than the calculator. I think it's just a crazy coincidence that you get half the calculator value. Also the calculator is based on cable to "free air" (i.e. cable is entirely on its own) whereas you have 2 power cables (red and black) and 2 signals (white and green for USB IIRC) all in a tight bundle - this will change the actual resistances measured vs calculated (yes can even reduce them due to induced currents etc). And (last) also the calculator doesn't know that the cable is made of 7Cores, and the skin effect changes the current capacity and therefore the "effective" resistance calculation. (BTW I hate doing these sort of calculations for work as so many variables to consider!)