Introduction: Coiling a USB Power Cord

Picture of Coiling a USB Power Cord

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

Picture of Materials

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

Step 2: Wrapping the Cord

Picture of Wrapping the Cord

Starting at one end of the pencil, tape down one end, leaving about 5 inches of slack. Wrap the cord around the pencil, leave another 5 inches of slack and tape down. Your wrapped part should be tight and not too pulled. 

Step 3: Setting the Cord

Picture of Setting the Cord

Using the blow dryer on high, blow hot air on it until the plastic is warm. Do this all over the pencil. You can hold the pencil on one end and do this or roll it across a table and blow dry all parts of the coil. 

Step 4: Let Cool and Enjoy!

Picture of Let Cool and Enjoy!

Let the cord cool until it is cold to the touch. Remove tape, you should be able to pull the pencil out and use your cord!


scroft1 (author)2014-04-20

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.
Steve (ex Plastics Engineer)

snoopindaweb (author)scroft12014-04-20

Thank You, I see the possibility's are endless, "Jumper Cables" maybe.?

JoelSP (author)snoopindaweb2014-04-22

Do you mean the kind you use to start one car with another? Because that wouldn't be a good idea...

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.

etcmn (author)JoelSP2014-04-22

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.

metalicmike (author)etcmn2016-05-01

It is inadvisable to coil power cords in this manner.The reason being that thay carry AC current and not DC.

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.

APoes (author)metalicmike2016-06-07

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.

TomaszP14 (author)APoes2016-08-10

Hey man! Thanks so much! I really needed a coiled cable for my project, but I couldent get one I needed, and hair dryer methode isnt really very good. I wanted to use oven, but didnt know what kind of temperature I needed. So thanks one more time. Now I have a coiled cable thats just like from a factory ! Chears

Yes, but....

Inductive reactance, impedance, is a function of both the inductance of the inductor and the frequency of the "signal".


- Your mains AC is 60/50Hz - so very low,

- And the coiled USB cable, or as many loops as you could possibly put in your extension cord will be such a tiny inductance,

That the reactive impedance (I in your equation) is wayyyy smaller, magnitudes smaller, than the resistance of the copper wire.

Take apart a speaker or a "wall wort" 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.

Questor (author)metalicmike2016-05-01

I was under the impression that USB cables carried DC, not AC

LesB (author)Questor2016-05-01


The battery charging current thru a USB cord is DC. Loading files thru a USB cord, that is AC.

ChrisB13 (author)LesB2016-06-07

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.

Ah, but your switching square wave "DC" data is AC. Lots of different frequencies of AC.

When you gave some serious time to kill, investigate Fourier transforms.

You'll learn that the nice square edges of your "DC" data signal have all kinds of high frequency components. That's why they put those "lumps" 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.

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.

But - no worry. The inductance we're talking about here, by adding coils to the cord, is soooo small that it's not going to do anything serious to the USB signal.

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).

The "don't coil extension cords" 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.

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.

LesB (author)ChrisB132016-06-07

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 "DC with an AC component".

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.

zencuke (author)LesB2016-05-22

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.

JohnW51 (author)LesB2016-05-01

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.

zencuke (author)Questor2016-05-17

@Questor Correct; USB carries 5V DC.

WannaDuino (author)Questor2016-05-03

how do you think you got your DC, always need AC for it,is for charging or as a mains to DC

zencuke (author)Questor2016-05-01

Good point but everything is sort of AC when it is turned on and off. It is not so much "alternating" current AC "changing" 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.

jimvandamme (author)metalicmike2016-05-02

A few microhenries at 60 Hz are not going to make much impedance.

zencuke (author)metalicmike2016-05-01

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?

Mark 42 (author)JoelSP2016-05-03

Cars run on DC, so inductance isn't going to be a big issue with coiled jumper cables.

HAL 9000 (author)JoelSP2014-04-22

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

JoelSP (author)HAL 90002014-04-22

It depends what you're using them for and how thick your cables are as they aren't all made equal...

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.

If two or more parts of the cable are touching each other then the amount of heat adds together.

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.

jongscx (author)JoelSP2014-04-24

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.

So, P=I^2*R is still gonna come up with the same thing.

HAL 9000 (author)jongscx2014-04-24

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

ipalic (author)HAL 90002014-09-09

If you remember electromagnetism.
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.

zencuke (author)ipalic2016-05-01

Only AC. Not an issue here.

itsjustmescotty (author)ipalic2016-05-01

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.

JohnW51 (author)jongscx2016-05-01

Correct! Do it if you like the idea. (Retired electronics engineer--44+ years in electronics.)

kenahoo (author)JoelSP2014-04-24

I liked the P=I^2*R part, but you lost me at "fair amount of heat". The resistance in any standard jumper cables (6-gauge or lower) is so low you shouldn't ever feel them get hot.

All the same, I wouldn't coil them up like this because they'd take up more room in the car.

A nice jumper cable banter is here:

Questor (author)HAL 90002016-05-01

DC current

itsjustmescotty (author)JoelSP2016-05-01

you should learn a little about electricity before you make comments like this, sigh.

snoopindaweb (author)JoelSP2014-04-22

Thank You. = Voted. : - }

j_hagen_97 (author)snoopindaweb2014-04-21

thats a great idea aha but youd need one hell of a pencil

snoopindaweb (author)j_hagen_972014-04-22


Bill WW (author)scroft12014-04-20

When I was a "youngster" plastic had not been invented. Had not heard of this trick either.

Emma B (author)Bill WW2014-04-20

Hey Bill, how old are you... 150? ;-) And don't you even remember the coiled cords on the wall telephone which enabled one to wander about the room while chatting to friends?

Bill WW (author)Emma B2014-04-21

Wow, you are good, Emma!

"The first man-made plastic was created by Alexander Parkes who publicly demonstrated it at the 1862".

I'm definitely old enough to remember coiled phone cords, but did not know how to make a coiled cord with a hair dryer!

I'm only 72.

the norm (author)Bill WW2014-09-09

I remember having a phone that did not have the coiled cord. I also remember the crank phone in the kitchen. We had the outline of the crank phone behind the dial phone until I was 12, and dad finally repainted the wall.

michaelmacnz (author)the norm2014-09-10

Those big crank phones had a pair of HUGE 1.5V carbon zinc cells... They were like gold in the 50's when I had a little .49cc glow plug plane motor..

Now they use a single LiPo the size of your finger at 3.7v

Bill WW (author)michaelmacnz2014-09-11

Yes Michael, I remember those large 1.5V cells, there were a bunch of old ones in our house when I was 10 years old. They had nice brass screw terminals. The batteries were dead; my friends and I cut them open and used the insides; for some reason we thought it was one of the ingredients to make gunpowder. Luckily we were unsuccessful.

the norm (author)Bill WW2014-09-11

You were thinking of the carbon core I think. You also needed salt peter and something else, it will come to me after I hit post. But all that does is burn with lots of pretty sparks if you just light it. I tried several silly things with it, but nothing ever went bang.

fredellarby (author)the norm2016-05-01

Sulpher. But don't tell anybody.

the norm (author)fredellarby2016-05-13

That was it!! Thanks, someone said Sodium Hydroxide or potash, didn't sound right.

AJMansfield (author)the norm2014-09-11

That 'other thing' is, of course, Sodium Hydroxide, AKA potash.

Nawaz (author)AJMansfield2015-01-24

Just a little note. Potash is a term used for Potassium bearing materials. Sodium Hydroxide is also known as Caustic Soda and Lye.

WannaDuino (author)Nawaz2016-05-01

thank you thank you, now I now how to make bombers. Hahahaha

the norm (author)WannaDuino2016-05-13

Actually, you do not know how to make a bomb.
I couldn't even get it to fire a rock out of a piece of pipe.
Actually, I'm lucky, if it had worked, I would probably have made a pipe bomb.

TheodorE2 (author)Nawaz2016-05-01

Slow down. I thought we are debating "curled cords" here ?

Questor (author)AJMansfield2016-05-01


About This Instructable




Bio: I enjoy making things. My making them is usually based on necessity, the fact that it doesn't exist, and/or buying it pre-done would ... More »
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