This is an easy way to tidy up cord that are too long or in the way. Great for the car or desk.

Step 1: Materials

USB cord for your device (Got mine at Dollar Tree)

<p>Nice one, it's an old idea, but no doubt many of the youngsters may not of heard of it. A very useful technique in and around the workshop, where stuff gets tangled. <br>Steve (ex Plastics Engineer)</p>
<p>Thank You, I see the possibility's are endless, &quot;Jumper Cables&quot; maybe.?</p>
<p>Do you mean the kind you use to start one car with another? Because that wouldn't be a good idea...</p><p>It would be ok as long as you made sure they were stretched out before you used them but with the crazy amount of current they can carry you could quite easily melt the cables if they were used whilst still coiled. I wouldn't take the risk in case somebody used them wrong.</p>
<p>Yea I was just wondering it this idea would work with an extension cord for my power tools. That's a lot more than a USB cable but a very small fraction of what the jumper cable need to carry (up to 1,000 amps). Power tools 15amp max.</p>
<p>It is inadvisable to coil power cords in this manner.The reason being that thay carry AC current and not DC.</p><p>With AC circuits any coil acts as in inductor thus increasing the impedance of the coil so tnat the I(2) R losses become greater thus producing heat.</p>
<p>Yes, but....</p><p>Inductive reactance, impedance, is a function of both the inductance of the inductor and the frequency of the &quot;signal&quot;.</p><p>Here,</p><p>- Your mains AC is 60/50Hz - so very low,</p><p>- And the coiled USB cable, or as many loops as you <strong><em>could possibly</em></strong> put in your extension cord will be such a tiny inductance,</p><p>That the reactive impedance (I in your equation) is wayyyy smaller, magnitudes smaller, than the resistance of the copper wire.</p><p>Take apart a speaker or a &quot;wall wort&quot; style power transformer to see how many coils of wire it takes (hundreds and hundreds...) to create a significant (in this case both reactive and desired electromagnetic effect) inductor at low (AC mains, or similar bass audio) frequencies.</p>
<p>I was under the impression that USB cables carried DC, not AC</p>
<p>BOTH.</p><p>The battery charging current thru a USB cord is DC. Loading files thru a USB cord, that is AC. </p>
<p>Data is also DC. Data goes through on a steady voltage, It just switches on and off quickly. AC refers to a waveform with a positive and negative voltage in respect to ground.</p>
<p>Ah, but your switching square wave &quot;DC&quot; data <b>is</b> AC. Lots of different frequencies of AC.</p><p>When you gave some serious time to kill, investigate Fourier transforms.</p><p>You'll learn that the nice square edges of your &quot;DC&quot; data signal have all kinds of high frequency components. That's why they put those &quot;lumps&quot; in your printer's USB cable. It's a ferrite inductor to reduce the high frequency radiation caused by the square waves you're talking about. otherwise they'd interfere with your WiFi and other stuff in your house.</p><p>But there is no free lunch. When you run your square wave through an inductor to reduce the high frequency emissions - you lose some of your signal. The nice sharp corners will go away and get rounded. Enough inductance and the waveform might be reduced to an unrecognizable, error filled mess.</p><p>But - <strong><em>no worry</em></strong>. The inductance we're talking about here, by adding coils to the cord, is <strong><u>soooo</u></strong> small that it's not going to do anything serious to the USB signal.</p><p>And for the guys who think that it's going to have some effect on the AC 60/50Hz (either inductive, or electromagnetic), I wish! We'd save so much copper if we could create any kind of significant effect from ten tiny coils of wire at such a low frequency. If you don't believe me, tear apart a speaker and see how many coils it takes to create enough force to move that paper cone back and forth at low audio frequencies (kinda in the ballpark of mains AC).</p><p>The &quot;don't coil extension cords&quot; warning is so you don't leave it in a lump and stretch it out to help the cord dissipate heart. Yes, heat. Run your vacuum cleaner for ten minutes and then feel the cord. It'll be warm to the touch, maybe even hot. But this heat is nothing magical. Just the high power/current required by your vacuum going through marginally sized wire. The current is high enough (don't get started about whether it's AC or DC, it doesn't matter here) that the resistance of the wire becomes significant. P = I^2 * R. </p><p>And while we're at it, the resistance causes a voltage drop in the wire (V = I * R) that may be noticeable in that light bulbs in the room may dim a bit when you turn on your vacuum.</p>
<p>Since the signal does not cross the zero line, it is basically DC, true. But when you switch DC off and on you end up with what's called &quot;DC with an AC component&quot;. </p><p>That AC component acts in many ways just like basic AC, and it will be affected by inductances in the line just like basic AC. Put a large enough inductance in a line and the switched signal gets averaged out to a smooth DC. This method is used in some DC power supplies to filter out the 60Hz ripple. The size of the inductor needed depends on the frequency involved. A 5 Gbit/s signal would not need much of an inductor to be significantly affected.</p>
<p>Technically not true. AC usually refers to sinusoidal signals with an average voltage and current of zero (i.e. they swing positive and negative and average out) or at least close to zero. On the other hand you are right about these signals cause impedance. In this discussion people are being sloppy and calling any signal that changes AC.</p>
<p>True, but the AC is VERY low power, not like the AC from a wall outlet. So the losses would not be important. In fact, there are many off-the-shelf audio, video and USB cords that are coiled like this.</p>
The inductance of the coil is a joke at the frquencies involved. A little knowledge is a dangerous thing. Companies make money off this kind of ignorance. They sell ridiculoisly heavy audio cable by saying that audio only travels on the wire surface when this effect only occurs at fequencies millions of times higher than audio.
<p>Just what are the frequencies involved? </p><p>Consider that the cable may be used for a USB 3.0 data transfer. USB 3.0 is spec'ed to transfer at 5 Gbit/s. </p><p>Unless the cable is shielded, the air-core single layer inductor formed by the coiling can have significant impedance at GHz frequencies.</p>
<p>how do you think you got your DC, always need AC for it,is for charging or as a mains to DC</p>
They carry both. There are 4 wires. One pair carries 5 volts DC and the other pair carries data, which is definitely not DC. They sell coiled usb cables and this talk of the coil affecting the signal is utter nonsense. It is like saying that weighing yourself with or without a cash register receipt in your pocket will make a difference
<p>From Wikipedia: The key in the definition is direction. This was the key in the great debate that Edison (proponent of DC) eventually lost.</p><p><strong>Alternating current</strong> (<strong>AC</strong>), is an <a href="https://en.wikipedia.org/wiki/Electric_current" rel="nofollow">electric current</a> in which the flow of <a href="https://en.wikipedia.org/wiki/Electric_charge" rel="nofollow">electric charge</a> periodically reverses direction, whereas in <a href="https://en.wikipedia.org/wiki/Direct_current" rel="nofollow">direct current</a> (<strong>DC</strong>, also <strong>dc</strong>), the flow of electric charge is only in one direction. </p>
<p>@JefferyD25. AC and DC normally refer to the power source. To most people AC (Alternating Current) means sinusoidal signals going full negative to full positive at a constant frequency and voltage. DC means constant value voltage or power input. AC and DC are both special cases but almost any power source will be one or the other. In electronics the wires with other properties are generally called &quot;signals&quot; or &quot;data&quot;. They are not called AC just because they change and therefor aren't DC. On the other hand AC and DC are not defined officially. The terms originally came out of the power industry but people use them whenever they find them useful. For example when talking about inductance the key issue is signals that change so it is tempting to call any changing signal AC in that context and there is no &quot;official&quot; standard to call you wrong. Just nit-pickers like me. ;-) From that perspective USB is called DC because the power input is constant. It has data signals which by definition must occasionally change to be useful but they are seldom called AC. Sometimes a square clock signal will be called AC but even that is unusual. Calling it AC doesn't say anything you didn't already know so it is sort of useless.</p>
The data pins carry a pulsing DC connection which alternates between digital low (less than 1V usually) and digital high (+5V); the two states of a binary computer... The only time data pins would be close to AC is in a trinary logic circuit using a positive voltage, a negative voltage, and near 0V for the 3 states, and even then, it would be pulsed DC which occasionally emulates AC current.
@Questor Correct; USB carries 5V DC.<br>
Good point but everything is sort of AC when it is turned on and off. It is not so much &quot;alternating&quot; current AC &quot;changing&quot; current that causes the problem. Thus the arc welder example described previously. It also depends on what effect you are talking about. A coil will generate a magnetic field with DC. That's how a solenoid works.
<p>Sorry mate, but your information is just plain wrong. If you follow this link you'll see how power cable manufactures do it. With long metal poles and industrial ovens heated to 230F (110C). It's the same process as coiling a USB cable, only on a more industrial scale.</p>
A little physics is a dangerous thing. :-) It is not just you but all this talk about inductance is true but the effect is so small as to be irrelevant. Do you know how many windings are in a transformer? Do you know why?
WOW, I thought I was the only one that got past day three in electronics school. THE inductance is a joke at 60 hz and with both side of the AC cord in rhe coil the cancel the almost non existent effect.
<p>&quot;THE inductance is a joke at 60 hz&quot; Really? Just try running a marginally designed 60 Hz inductive load device ( read - most US products) at 50 Hz and measure temperature rise. I had one hour long chat with GE engineers about how to safely use a 60 Hz US model AC in India on 50 Hz supply. It was an eye opener. Even your low power transformer based AC adapters will heat up under these conditions. </p>
@pmshah You have totally distorted what I said. I said the inductance of a coiled jumper cable or some usb cord is a joke at 60 hz. It is a bigger joke at 50hz. This has absolutely NOTHING to do with electric motors with inductances millions of times bigger than some coiled up cord. I am well aware of problems that can arise trying to use 50 or 60 hz devices at the wrong frequency. Talking to some clerk at GE customer service is no substitute for some basic electronics school.I worked electronics in design, production and repair for 50 years and this whole discussion is a bunch of people throwing around terms that they barely understand.
@pmshaw: Most smaller appliances have an adapter to easily switch from 50 to 60hz. You've probably seen them. They are designed for both standards to keep inventory low; they can sell the same design in multiple countries. The problem with quoting someone else (GE engineers) instead of speaking from your own knowledge is you don't know what caveats and conditions they didn't have time to tell you. There are devices that will do poorly when switched from 60 to 50. Usually they have transformers with LOTS of tightly packed windings around iron cores. Either that or electric motors with the same properties. (electric razor!) I'm guessing that was too complicated a story for your GE buddies. Some common devices are dangerous at the wrong frequency so they told you about the worst case to make sure their advice didn't kill you. A loose widely spaced coil with no iron core like we are discussing here will have minimal inductance. Trust me the GE engineers were not talking about that situation. A good electrical engineer will know at least as much physics as I do, the good ones anyway. And working at GE is no guarantee. Unfortunately there are a depressing number of sloppy and/or lazy engineers who couldn't calculate their way out of a Goodyear blimp hanger with a tail wind and the doors open. I'm sure some of them work at GE.
<p>I lived in US for 6 years and brought a whole lot of used equipment back with me when I returned to India. At that time ALL the ac adapters were transformer based and there was no such thing as SMPS designed for international use. and believe me they did run hot and not warm. Blenders mixers and electric irons, almost purely resistive loads were an exception as they were universal type AC/DC operable. The advice of the GE engineers - specific to their A/C unit - worked perfectly and I used my 6 year old - from US use - for 10 more years when finally the plastic body simply fell apart. So don't discount everything out of hand. &quot;THE inductance is a joke at 60 hz&quot; may be true for the specific situation relating to the application here but certainly not in all situations. BTW US made high speed, high volume photo processing machines that I dealt with for many years used motors which were specifically designed for 50 Hz. </p>
<p>A few microhenries at 60 Hz are not going to make much impedance. </p>
TRUE but it sounds like most if these guy took the short bus to electronics school and don't know a Henry from an O'Henry. Besides you have both sides of the cord there which cancel out. That is why you need a line splitter to use a clamp on ammeter.
<p>&quot;Besides you have both sides of the cord there which cancel out.&quot;. You are right. That is how Bifilar windings work to make non inductive load resistors. </p>
<p>no only a bit yES, but if you say the a cable on AC is no danger, your the little prick here</p>
<p>and for your info before you think again your OWN story's,like the Flinstones,</p><p>In a coil on a role an Carry hight watts and Amps.</p><p>They to temp messure iT.</p><p>But ONLY IN A LONG TIME IT WILL BE DANGERUS.</p><p>IS IT CLEAR NOW.</p><p>MY GOD WHAT A STORY MAKERS HERE</p><p>So no DC .</p>
Coiled AC line cords are a common item. The inductance of an air core coil of a few dozen turns at 60 hz is a joke.. Besides, you have both sides of the AC line there that cancel each other out. AC chokes are usually in the Henry range and you are talking about micro Henrys
Not all cords are cords are thermal plastic that gets soft when you heat it. Some are rubber that can tolerate quite a bit of heat until it starts to burn. You don't mean 1000 amps but 1000 watts The total srvice for my whole house is 200 amps. 1000 watts is about 8 amps at 120 volts AC line voltage.
wait, what? Why would they behave any differently when they're coiled? my jumper cables haven't even gotten noticeably warm to the touch with use
<p>It depends what you're using them for and how thick your cables are as they aren't all made equal...</p><p>Basic laws of electricity give the equation of P=IxIxR, Power = Current squared times the Resistance. A car's starter motor for a large vehicle can draw up to 600Amps so even with a low resistance ie. thick cables, you can end up with a fair amount of heat.</p><p>If two or more parts of the cable are touching each other then the amount of heat adds together.</p><p>It would probably be fine if you stretch them out before you use them or if you've got decent cables and a small car and it starts quickly but the worst case scenario could be pretty bad hence my advice against it. It's up to you if you do it, but I'd say better safe than sorry.</p>
<p>I'm still not convinced that IS the reason why you shouldn't do it. Resistance is based on material property*material cross-section*material length. You're not changing any of these things, it's still copper, the wire is still just as thick as before (or that's one hell'a powerful hair dryer), and it's still just as long, albiet coiled up now.<br><br>So, P=I^2*R is still gonna come up with the same thing.</p>
<p>I think he was mostly concerned with the cables having a reduced capacity to dissipate heat if some of the coils are touching. Still, it shouldn't have any *real* effect, unless you throw a blanket over the top of it or something</p>
<p>If you remember electromagnetism. <a href="http://en.wikipedia.org/wiki/Electromagnet" rel="nofollow">http://en.wikipedia.org/wiki/Electromagnet<br></a>That's why you shouldn't coil power cords, of any kind. It induces magnetic field that creates force opposite of the current that flows through the cord.<br></p>
<p>when I was welding and bored, many years ago, we would wrap many feet of welding lead around a copper tube with some metal rod inside then strike an arc - 250 amps 26 volts DC and propel the metal across the room. Even better was 600 amps gouging current. </p>
Cool!! You built a giant solenoid. It was a single conductor and DC and gobs of current. These gus are talking about 2 conductor AC at low current and are all spouting terms that they barely understand. I really like your experiment.
It us called inductive reactance. You better not coil up an extension cord in your living room. The magnetic field will attract the screws in your big screen TV and rip it off the wall. You learn a tiny bit of electronic theory and haven't a clue how it works in the real world. Getting back to your original statement at 60 hz the <br>Inductance of the coiled up cord is a joke.
Only AC. Not an issue here.
I agree but I just noticed a tag in an extension cord saying to uncoil before use. Their lawyers probably advised them to say it. They warn you about every possible senario to cover themselves if sued. Everything I buy comes with an instruction book that has three pages of warnings before they get to the instructions.

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