Questions tagged [cables]
Questions about cable types, properties, ratings and construction.
954
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Securing electrical cables to holes in enclosures?
Suppose I would like to insert data-cables of varying diameters -- e.g., a cable of 5 mm diameter -- into the 6 mm diameter hole of a plastic enclosure. The wires within the cable are terminated via ...
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votes
2
answers
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In a USB cable, is it OK to swap the D+ and D- wires?
I heard that D+ and D- are differential signals, does it matter if I swap them when connecting a USB device to the computer?
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56
votes
10
answers
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Why is an Ethernet cable not grounded?
There is no dedicated GND in the classical Ethernet 8P8C ("RJ45") pinout.[1]
Why does the Ethernet spec not include a ground, unlike many other cable types used for interconnecting devices that may ...
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52
votes
9
answers
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Why are copper cables round?
Why are cables only made of round shapes? What is the advantage of it? Why aren't there triangular or quadrilateral or pentagon shapes of cables?
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11
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Why isn't stripping wires by burning with a lighter a more common practice?
I see people suggesting specialized tools, or trying it manually with sharp knife or scalpel, why not just burning the rubber for a second or two with a lighter and just pulling it out a more ...
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47
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7
answers
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Why aren't headphone jack shaped plugs used for data?
With Apple's lightning cable, and USB 3.0, reversible cables are taking off, and I personally think this is very convenient. But we have had better than reversible for a long time, in the form of the ...
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votes
10
answers
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Can a premium HDMI cable outperform a standard cable?
Assuming two cables both conform to the same standards (e.g. HDMI2.0, high-speed, ...) is it possible that a premium cable will outperform a standard cable when using an objective benchmark that ...
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38
votes
7
answers
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Why were coax cables used for networking?
Often, if older standards become obsolete, it's because they are superseded by newer technologies. In the past networking was done using coax, instead of the twisted pair used today. Why did they use ...
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37
votes
3
answers
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What are those weird wires in the audio cables?
Trying to repair a headset cable, I discovered that it doesn't look at all like the “ordinary” cables I used to repair. I was expecting to see, inside the cable jacket, four wires, each one in a wire ...
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32
votes
8
answers
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Why is it dangerous use a coiled extension cord?
What aspect of using a coiled extension cord makes it more dangerous than using an unrolled power cord?
Many fire safety websites say that an extension cord should not be used while coiled.
Is this ...
- 2,415
30
votes
8
answers
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Can I use I2C over 2m cables?
In my current project, I need to communicate between a microcontroller and some sensors over I2C. One of them is a temperature sensor, it needs to be placed at approximatively 2 meters far from the ...
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3
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What does "no fit" mean in electronics?
I have found at some places, especially:
Raspberry Pi Forums
eLinux RPi Hardware page
the following wording:
S2: DSI interface. 15-pin surface mounted flat flex connector
(possibly no-fit) S5: ...
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26
votes
5
answers
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Just chopped a cable, is red power, black ground?
I've just chopped a usb to micro-b usb cable.
There are 4 small wires inside
Red
Black
White
Green
Isn't it universal that Red is power and black is ground?
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26
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8
answers
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Is CAT5 cable good enough for RS-485 vs "true" RS-485 cable
I have a serial comms project coming up. A number of boards with RS-485 interfaces need to communicate. Date rate is 57600bps and cable length will be less than a few hundred feet.
Will shielded ...
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25
votes
4
answers
5k
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Pass USB 3.0 connection through D-SUB connector
I need to pass a USB cable through a vacuum chamber wall, for which we have only D-SUB passthrough flanges available. So I cut a USB cable in half and soldered a D-SUB connector to each half. For USB ...
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23
votes
4
answers
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How is xΩ impedance cable defined?
This is probably a really simple question, but I can't seem to find a definite answer anywhere.
I'm guessing 50Ω cable means 50Ω per unit length.
What unit length is this? If this is not how its ...
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23
votes
5
answers
12k
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What's the best cable to transfer audio signal?
Sorry if this is the wrong place but I'm interested in a scientific and electrical explanation and not some HiFi voodoo magic.
I guess you all have seen the discussions about expensive audio cables ...
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22
votes
7
answers
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Why is USB Type-A to USB Type-A never used?
I was wondering why almost all USB cables that exist are USB-A to (Micro-USB | USB-C | USB-B | etc.)
Why was USB-A to USB-A not a popular thing? Is there a technical reason this cannot work?
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22
votes
7
answers
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Is it bad practice to parallel power connector contacts?
Say I'm looking for some power connectors for a design, the current requirements are quite high and although I could get a connector with contacts rated for the full current, they're so bulky that ...
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22
votes
2
answers
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Maximum cable length for 3.3V UART signals
I would like to avoid using RS-232 converters between two microcontrollers on two different boards. For various reasons, only UARTs are supported, e.g. no SPI or I2C, and I will be using CAT5E cable ...
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18
votes
2
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Is there a minimum length for SATA cables?
Today I stumbled across a piece of information that surprised me. Apparently there is a minimum cable length for SATA. From Seagate, a reputable manufacturer of SATA devices:
Serial ATA (SATA) data ...
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18
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3
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What does an EV "wall socket charging cable" do?
Known as "Mode 2 charging", this method of charging electric vehicles describes the use of a common household wall socket and common mains voltage (230 v) to charge the vehicle. This is ...
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18
votes
3
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What are these teardrop-shaped loops in power lines for?
I just happened to notice this along a road near where I live:
So these were in a pair, oppositely facing, "tip" to "tip" of the teardrop.
At first glance, this doesn't seem to be ...
- 1,236
17
votes
6
answers
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Max Serial Cable Length?
What is the maximum length of serial cable I can use, to connection work properly? Is length of serial cable in connection with baud rate? I am using about 5 meter cable at speed 38400 bauds and RS232 ...
- 1,009
16
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2
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Terminating shielded/screened twisted pair correctly
Theoretically, I can't see a problem if the twisted pair has an end of cable termination that is: -
A single resistor (R) that matches the characteristic impedance of the cable placed across the two ...
- 1
16
votes
2
answers
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Twisted Pair Twist Rates
What are the mathematics behind twisted pair cabling? I know that the twists are there to help eliminate cross talk and interference, but I want to know about the math of how they find the specific ...
user2859
15
votes
6
answers
5k
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Is there a low-cost alternative to RJ45 cables for large number of signals?
We are designing two interface (printed) boards and need to connect them by cables (0.5-1.5m). So we're thinking about which connectors to use. We'd like to use twisted-pairs like in a RJ45 cable.
...
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15
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5
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Why do we still use cable for a lot of forms of data transmission?
Like many people I'm often annoyed by ugly cable clutter, especially when it's long distance. In my opinion it would be ideal if cables could be eliminated altogether, so that you'd just have two ...
user9878
15
votes
3
answers
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How does "bidirectional" transmission on gigabit ethernet work?
I was reading about the various twisted pair protocols, being distracted by the marvels of Wikipedia when I went to look up the way to wire a connector.
And I'm wondering how it can transmit in both ...
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15
votes
3
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380
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Communication among briefcase halves
I'm building a small laptop-ish device in a briefcase. Imagine the green wires aren't there. The LCD half lies somewhat deeper in its case than the keyboard part.
For now, testing and programming, I'...
user17592
14
votes
12
answers
41k
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Avoiding DC voltage drop over long distances
I am trying to power my IP camera over a long distance from the power socket (about 10m). The included power adapter, rated for 5V 2A is about 1.5m long.
I cut the cable and extended it using a ...
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14
votes
8
answers
8k
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Apple power supply: thick AC cable, thin DC cable - why?
Apple power supply consists of a very thick, inflexible AC cable (wall outlet to converter) and a very thin, flexible DC cable (converter to computer):
Why? The currents through the cables should be ...
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14
votes
4
answers
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Are there any advantages to using rigid RF coaxial cables?
While watching this Signal Path video, I came across this shot:
I saw few rigid coaxial cables there and so I started wondering what might their advantages be. I could only find disadvantages:
They'...
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14
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3
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Why do thunderstorms knock out power?
It isn't like lightning strikes the wires. And surely the whole apparatus is designed to be water-proof. So what is it that causes power outages during thunderstorms?
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14
votes
1
answer
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Wiring diagram for USB-C to USB-A cable?
I make USB cables (USB-A to Mini or Micro primarily), but don't have any experience with USB-C. I would like to create a cable that has a USB-A (2.0) connector on one end, and a USB-C connector on the ...
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14
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6
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3k
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Piezoelectric effect in cables?
I am using a very sensitive transimpedance amplifier on a 3m long cable to a photodiode. Signal levels are about 70 nA - 700 nA. Bumping into the cable causes a large voltage spike on the output of ...
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14
votes
2
answers
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3 wires on a (bipolar) DC plug - what are they for?
If got this cable as a power plug for my DELL XPS 15. I want to hook it up to a different power source.
But what are the 3! wires for on a bipolar plug?
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14
votes
0
answers
798
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Why is there a textile thread in some cables [duplicate]
Here is a photo:
I have seen many cables with a single textile thread in them and I always wondered why it is there.
Does anyone know?
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13
votes
4
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4k
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Heat-shrink tubing available as a roll like adhesive tape?
Many people who have used heat-shrink tubing have probably experienced this: you forgot to insert heat-shrink tubing before soldering, and now it's too late!
Indeed, once the soldering is done:
you ...
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13
votes
2
answers
14k
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Why is current rating for multicore cable lower than single core with the same cross section?
As per this resource, a single core 10 AWG (5.3 mm2) copper cable is rated for up to 52 amps, while the same cross section cable of 43 cores and more is only allowed to carry up to 15 amps.
Why is ...
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13
votes
5
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40k
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Bring 5V DC 20 meters away
Sorry if my question is stupid but I'm an electronic passionate only during the weekend.
I had a talk with a friend, we want to bring the power supply to a box containing a microcontroller inside a ...
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13
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1
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Why must USB low-speed devices use a captive cable?
The USB 2.0 spec says: "A low-speed device is required to have a captive cable." However, I can't find a good explanation for why this is the case. I have seen hints towards two possible ...
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4
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Why does the current carrying capability of a cable increase with temperature
I'm specifying cable for a VFD application and came across this table regarding NEC ampacities and corresponding cable size.
What I found interesting is that the ampacity increased with temperature ...
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12
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6
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9k
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What makes a high speed USB cable high speed?
I was shopping around for USB 2.0 cables.
Some manufacturers claim their cables are "high speed".
My understanding is that the electronics on the device determine the speed, not the cable.
I ...
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4
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Why do cables have multiple grounds?
Many cables have multiple grounds. Why?
For example, according to Wikipedia:
The SATA standard defines a data cable with seven conductors (3 grounds and 4 active data lines in two pairs) and 8 mm ...
12
votes
2
answers
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How does a ferrite core wire terminator work to reduce EMC?
The following question was asked on superuser: What is that cylinder on cables?
How does that cylinder work? As far as I can tell, even if you put one on either end of the cable, any HF signal should ...
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12
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3
answers
6k
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Software for creating cable schematics
I'm looking for free software to create drawings of communication cables eg. DE-9, RJ-45, Ribbon Cables, and Molex. I can't seem to find any software that comes with images of the connectors that can ...
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4
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Cable shielding (best practices)
I am making a cable to connect two boards as shown in the image below:
The cable will be around 25 cm long and will be in an electrically noisy environment (consider 220 VAC house wiring lines ...
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11
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4
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4k
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When wiring a European (Schuko) plug, what thing should I focus on not to mess up?
I know this might be a dumb question, as wiring a plug isn't some rocket science, but I am wondering if there is something not so obvious that can go wrong, or any tip at all for me to care when doing ...
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5
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Why don't we use 7075 aluminum Ethernet and USB cables?
Since the skin depth of copper at 1Ghz is about 2.3 micrometers, it doesn't seem like aluminum would provide a worse signal to noise ratio.
7075 aluminum is also much more resilient and stronger than ...
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