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SparkFun Hydra Power Cable - 6ft

$ 5.50 $ 2.50

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Behold, the Hydra! This USB power cable probably looks a lot like something you've hacked together before. We do it all the time, because what is a computer if not a 5V power supply that happens to run software?

The Hydra brings the 5V and GND lines from your USB power supply, computer or otherwise, and breaks those lines out into three common power connectors: Barrel Plug, JST and Alligator Clips! The clips are shrouded to avoid shorts and the barrel plug is center positive. The cable is 6 feet long overall which give you plenty of room to work.

Remember that USB power does have its limitations. Most USB hosts will only provide between 100 and 500mA at 5VDC.

Warning: Due to a defect by the manufacturer, the polarity on the JST connector on this cable has been reversed. The cables can be swapped after purchase, but please do not plug the JST connector in as it is. Additionally, since these cables are being retired due to this defect, once we are out of stock, we will not carry it again.
  • 6' Long

SparkFun Hydra Power Cable - 6ft Product Help and Resources

Connector Basics

January 18, 2013

Connectors are a major source of confusion for people just beginning electronics. The number of different options, terms, and names of connectors can make selecting one, or finding the one you need, daunting. This article will help you get a jump on the world of connectors.

Core Skill: Electrical Prototyping

If it requires power, you need to know how much, what all the pins do, and how to hook it up. You may need to reference datasheets, schematics, and know the ins and outs of electronics.

1 Electrical Prototyping

Skill Level: Noob - You don't need to reference a datasheet, but you will need to know basic power requirements.
See all skill levels


Looking for answers to technical questions?

We welcome your comments and suggestions below. However, if you are looking for solutions to technical questions please see our Technical Assistance page.

  • The Crazy Maker Guy! / about 6 years ago / 1

    Everyone The Polarity is reversed BUT its a easy fix. Just reverse the red and black wires.

    I emailed SparkFun about this and they are seeming to do this from some internal standard different from the batteries.

  • MDGeist / about 8 years ago / 1

    Well, Good thing I checked here and the review, BEFORE plugging this thing in! As of a week ago, the polarity is STILL REVERSED on the JST...AND... NO official comment!! Those Chinese cables are looking better all the time.

  • Drun / about 12 years ago / 16


  • tld / about 12 years ago / 7

    There's so many things wrong with this cable, that I can't stop myself from wanting one.

  • Gregly / about 12 years ago / 4

    I want a USB-to-115v mains cable just to annoy all the people that freaked out over the Cerberus cable.

    • Sleepwalker3 / about 11 years ago / 3

      Gotta upvote that one, love it! But what about a 240V - USB for those in other countries? :D

    • Oh, that's no problem. A regular automotive inverter will do you just fine. 5v is close enough to 12v to work, right? You might get a bit of noise, but who cares.

    • K3QVKen / about 12 years ago / 1


  • scicior / about 12 years ago / 4

    Something my Grandpa taught me a long time ago, if you are going to make a "Suicide cord" (what he called a 110V cord with two alligator clips on them; useful for powering TVs you are repairing with the back case off), make the two leads to the alligator clips two different lengths. That way, they are less likely to touch each other and short out!

    • Steven Ciciora

    • Sleepwalker3 / about 11 years ago / 2

      Sounds like a smart man your Grandpa. 110V is only a tickle lead, try it with a 415V 3-phase 'Death lead' as we call them.

      • Citros / about 10 years ago / 1

        Voltage doesn't kill you, current does.

        • Sleepwalker3 / about 10 years ago / 2

          Well actually it's the Power, not Voltage or Current on their own (obviously the current is limited by V and R). Power is equal to V squared / R and so when you double the voltage at a given resistance, you quadruple the power dissipated - essentially there's a lot more thump on the heart with increased voltage. But either way, they are all more than enough to kill you, so my joking about a 'tickle' above shouldn't be taken seriously, so always play it safe.

          • Citros / about 10 years ago / 1

            50mA across the heart is enough to interrupt someones heart beat anything above 50V is considered a possible lethal voltage

            • Sleepwalker3 / about 10 years ago / 2

              Yes, indeed I would think far less than 50mA would. It's already been proven that a 1.5V AA can stop the heart, it's all a matter of where the voltage is placed (across what points) and hence how much current actually flows through the heart.

  • Member #229304 / about 11 years ago / 2

    Am I the first one to notice this... the JST polarity is the wrong way round!

  • Member #125582 / about 11 years ago / 1

    Could I safely use this to power a Mega with with the 5V 1A USB wall charger? https://www.sparkfun.com/products/11456

  • K3QVKen / about 12 years ago * / 1

    Just do what I do...just clip one clip to the wire or something else insulated on the cord. Cheap, easy and doesn't cause a cool product to be expensive or overly engineered.....If you need all that extra flexibility, make your own adapters, or your own 10 legged cord. Just sayin..... ;)

    • Sleepwalker3 / about 11 years ago / 1

      Yes I've done that in the workshop lots of times and 'usually' it's fine, but it's that one time when something moves a bit and the alligator clip flicks off and ...BANG Yep you can make your own if you want something fancy, but isn't this actual product something you could make yourself and a bit fancy? It's a good thing, very handy, I just think it could be improved.

  • raymohi / about 12 years ago / 1

    Would be nice if there was a version that went from banana plugs to alligator clips, barrel plug, and more banana plugs. That would be great for bench power supplies..

  • John Laur / about 12 years ago / 1

    I forsee a problem where you are using the barrel jack and the alligators short out and ruin your fun. Ether the alligator clip should have a longer sleeve (so it can be fully protected) or the alligator clip version should be a standalone cable...

    • RocketGuy / about 11 years ago / 1

      I'd just get a non-conductive item, piece of wood or plastic, and clip both clips to it. For extra points, it could be shaped so that there is a non-conductive bumper all around and a barrier between the two clips. Or drill pairs of holes to clip into in a chunk of wood...

      I leave the rest as an exercise in creative design for the student.

    • Sleepwalker3 / about 12 years ago / 1

      I fully agree, the alligator clips should be made detachable, by doing away with the alligator clip part and having a 'barrel jack (socket) - flying leads with alligator clips' unit that can plug into the existing barrel jack, that way you don't need have to worry about the alligator clips touching on your project and damaging something when they aren't being used. You just plug them in when you want them.

      • Member #197750 / about 12 years ago / 1

        As stated above - "any USB port that actually conforms to the USB spec should have usb protection built into the port itself. Each USB port typically has it’s own power switch and will automatically shut off in the event of an over-current situation. If you have proper drivers, you OS will even notify you." ... "we tested it with the alligator clips clipped together and never had a problem. it’s not necessarily wise to do this, but at the same time, if you accidentally do, there shouldn’t be an issue."

        • Sleepwalker3 / about 11 years ago / 1

          It's a known fact that it doesn't always work and that not all USB ports conform, what 'should' meet the standard may not. In any case, would you like a +5V alligator clip to accidentally touch your 3.3V micro in some random place, just because something moved? 500mA is more than enough to damage many 3.3V chips in that scenario. I can also see many people plugging this into one of those wall-wart style USB supplies that can supposedly supply an amp or possibly more - likely just a largish electro on the output of those. I expect SF sell them even. Far better to be safe than tempt fate and in any case a Barrel Jack - Alligator clip plug would like be a handy product all on its own - Suddenly SF have another new product :)

        • Zmaster / about 12 years ago / 1

          Even if your PC probably won't die because of this, there are situations where it would be surely better to not have those alligators clips hanging out. Think about non-properly designed USB hosts and hubs (i don't even want to know...). Or powering your circuit with the plug and then having the clips make a short on ICs.

          Detachable clips sounds like a good compromise to me.

  • cairn / about 12 years ago / 1

    That's a barrel plug, not a barrel jack, right? It also doesn't state the size of the plug (I'm guessing it's the 2.1mm center variety).

    • It is a plug, sorry. And yes, it's intended to fit the Arduino and other products on our site that have a 5.5x2.1mm, center-positive barrel jack.

  • Alfonso82 / about 12 years ago / 1

    I think that it you guys should have put some kind of short circuit protection, cuz I'm seen a lot of burn out USB ports or even motherboard, just a thought. A diode will do the job but it take 0.3 to 0.6 volts down ;)

    • Sleepwalker3 / about 12 years ago / 4

      A diode will not provide any sort of short circuit protection.

    • jbookout / about 12 years ago / 2

      I disagree. If I purchased this I wouldn't want random unmodifiable components hidden in the cable. A cable like this IMO should contain only copper...and terminators of course.

    • tecmec / about 12 years ago / 1

      Actually, any USB port that actually conforms to the USB spec should have usb protection built into the port itself. Each USB port typically has it's own power switch and will automatically shut off in the event of an over-current situation. If you have proper drivers, you OS will even notify you.

      • this. we tested it with the alligator clips clipped together and never had a problem. it's not necessarily wise to do this, but at the same time, if you accidentally do, there shouldn't be an issue.

        • John8 / about 12 years ago / 3

          Right. Keep in mind that these protection circuits aren't perfect though. I have a friend who was powering a project off of USB and accidentally energized the circuit with reverse power from another source. The result was -5V applied to the USB bus. Luckily his Mac was still under warranty and he was able to bring it in, act all unknowing-like and say "it doesn't work anymore." I've had similar problems when a project was drawing pulsed power and may have been injecting some RF.

          Bottom line: Be smart. Your computer is convenient for many things, but it's a whole lot more expensive than an LM8705 to replace.

Customer Reviews

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10 of 10 found this helpful:

WATCH OUT! - JST polarity is backward

JST polarity is backward... errr well different than anything I've come across, lithium batteries, Fio V3, Arduino Pro, SAMd21

OK... I can't blame this ALL on the connector but who else am I going to blame for smoking my brand new board..... :(