Questions tagged [cables]
Questions about cable types, properties, ratings and construction.
87
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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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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 ...
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15
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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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59
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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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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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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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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26
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8
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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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26
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5
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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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23
votes
5
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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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10
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1
answer
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How to calculate voltage drop over and power loss in wires
How do I calculate the voltage drop over wires given a supply voltage and a current? How do I anticipate on voltage drop so that the final load has the correct supply voltage?
What will be the power ...
user17592
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4
answers
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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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56
votes
10
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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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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
0
votes
1
answer
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Connect SMA to a regular pin/wire
I have an RF signal (5ns pulses every 200ns) coming out from a SMA connector on FPGA board (Spartan 3E Starter Kit). I want to send this signal back to the FPGA using one of the on-board pins.
So, I ...
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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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votes
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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votes
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
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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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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9
votes
3
answers
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Does the position of the Ferrite bead matter?
Often I will see a ferrite bead a couple of inches from one end of a cable. Does the position of a ferrite bead really matter?
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6
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In a multicore cable, what is the nylon "string"?
I am using 4 core shielded cable. However, there is a strand of what I assume is nylon running parallel to the conductors. A bit like this
(source)
What is it for?
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Sending I2C reliabily over Cat5 cables
I am considering implmenting an home automation system around my Raspberry Pi but I found the price and space requirement of inserting a Pi every place some control is required too much but the Cat5e ...
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6
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What's the rationale behind these warnings about extension cords?
(Disclaimer: I've read the help center and I do understand that this is bordering on off-topic since it's about consumer devices. However I hope that I've managed to make enough on-topic by asking ...
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votes
3
answers
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How to determine appropriate speaker cable gauge?
When wiring speakers to a 100W consumer-grade amplifier, how do I select an appropriate gauge cable (for 8-ohm speakers)?
Also, if 14 gauge cable is sufficient, what harm is there in using a heavier ...
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votes
3
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Does USB Power Delivery handle USB cables that are not PD-aware?
I think USB-PD is still fairly new (I don't know anyone who owns a device that has it) but reading wikipedia and info sites does not make it clear what happens when you use a cable that is out of spec ...
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6
votes
3
answers
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Why is Cat5/Cat5e Ethernet cable rated 100MHz?
As the questions says, is there any specific reason why Ethernet cable is rated 100MHz?
For a 100Mbps Ethernet the data rate is 100Mbps, and the baud rate is 125Mbaud, because of the specific line ...
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votes
1
answer
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Y USB Cable with external 5V supply
I just got a brand new Nexus 4 phone and am a bit dissappointed that it doesn't support USB OTG. One reason is that is doesn't supply 5 V out of its USB port, as opposed to other Android devices I ...
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3
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High voltage cable cross section
What kind of power and voltage can the cable in the photo possibly drive and why is it composed of a lot of small cables? What if the diameter of the single copper cables were a little bigger? How ...
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5
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Any truth behind "multipole" technology in audio signal transmission?
After reading this question about ultra-expensive audio cables, I was reminded of a product that we sold at a company I used to work for.
MIT Cables makes these "audio interfaces" which go a step ...
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1
vote
1
answer
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I2C on FFC or IDE cable - interference?
This is a follow-up question on this answer. I need to communicate with I2C over approximately 10cm and I'd like to use an FFC or IDE cable for that.
Earlier, I used an FFC cable to link a segment ...
user17592
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vote
1
answer
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USB Charge and data separate cables
Is it possible to split micro USB to USB cable so two cables (data + and data -) go to the PC with USB and two other power cables go to power brick?
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2
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Cat 5 cable 100MHz bandwidth meaning
Category 5 cable on Wikipedia:
The bandwidth of category 5 and 5e is the same (100 MHz) and the physical cable construction is the same, and the reality is that most Cat 5 cables meet Cat 5e ...
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0
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3
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Is the maximum rated current of the cable the same for any voltage?
Cat5e cable has a rated current of 0.577A (wiki page). I am wondering if this is voltage dependent? I am almost certain it is not, but if it is, something might blow up. Say I need to get 2A at 5V ...
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0
votes
3
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Measuring length of two wires inside copper with a TDR
I have a cable as in the drawing.
The black parts are insulators and the brown parts are copper, so there is a big copper cable and inside are two smaller copper cables.
When the big copper cable is ...
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0
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1
answer
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Help with voltage regulator [closed]
I’m very confused on how a voltage regulator is used. On this one that I found: Fasizi 3.3 DC Voltage Regulator 4.75V-12V to 3.3V 800mA, I have no clue where which cables should go where. If I use a ...
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2
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Cable type and decreasing EMI/RFI
I am interested which cable/wire type is better to protect against electromagnetic and radio interference/leakage of signal.
Is a twisted pair wire better than an untwisted, to protect against EMI/...
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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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7
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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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7
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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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15
votes
3
answers
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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
8
answers
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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
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0
answers
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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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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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12
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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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4
answers
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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 ...
11
votes
3
answers
18k
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How do network devices detect whether an ethernet cable is connected?
I have a bit of kit with an FPGA on it which includes an ethernet adapter. I'm trying to diagnose why it's not working and while I do that I've noticed that with an ethernet cable connected to my ...
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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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votes
2
answers
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How does a coaxial aerial cable work?
My family and I managed to break the aerial cable of our TV a few days ago.
The cable is of this kind of design:
And I believe its called a coaxial cable.
Fortunately, someone more practical than ...
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votes
1
answer
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How do Tx / Rx cable pairs work in an Ethernet cable?
This question will be a simplification as I lack the proper knowledge.
Lets suppose we want to send a signal over the network. We will use this scheme as this is hopefully how the signals are send ...
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