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Can I use a mini jack to power things up? Answered

Hi, first of all I must apologize if I'm not being clear on the description of what I'm planning on doing (english is not my first language), there's a drwing if it can help understand what i'm trying to say.
So here's my "problem":

I have been building several devices (small LED lamps, robots and other geeky stuff I found here on Instructables) and I'm trying to find a good and "universal" solution to power them. Their energy consumption is low so I decided I could use a USB connection as the power source/supply.
Now, I would like to use a single cable to power all these, a "plug and play" solution and I've been thinking to jacks, the kind you find on headphones: easy to plug/unplug and I've got plenty of spare female jack plugs I can use with the devices (with the appropriate resistors included).

So basically I would end up using a cable with a male USB on one end and a male mini jack on the other.

Is it possible to use the jacks this way?
Will the mini jacks and/or the headphones cables stand the power from a USB source?

Thanks for your answers!


Yes it will work, just be careful with how you wire the jack:

You want the ground (- connection) to go to the RING, at the base of the mini jack, and you want the +5v to go to the very tip - then its less likely you'll short out the connection.  The computer's usb port SHOULD be connected from short circuit, but I've wrecked more than a few by shorting things out. 

Thanks for your answer (it also applies to the others! Now I know with certainty the USB port can provide 5V :-) ). I should not overload my USB since I'm mostly using small LEDs (2 max) or small circuit boards.

But now I have a new question:
You (frollard) raised the matter of the "ground wire". From my memories of electronics in school, the ground is used as a protection against short circuits by diverting the electricity caused by a miswiring to....the ground where it's rendered harmless for the device components.

But on a USB there are only 4 wires: 2xData, 1 positive and 1 negative. Where do I  solder my ground wire from the jack?

Again: thanks!

*in general* but not always the voltages will be marked.  If something is +5v that's 5 volts ABOVE ground (zero).  Computer power supplies have a negative ground, so the +5, +12 are above ground volts, where the current flows from +5 to ground (the electrons flow the other way, but thats electrical engineering for you, being invented before electrons were common knowledge, and 'doing it wrong' stuck.)

Computer psu's also usually have a -12 rail, so you have -12, ground, +5, and +12 volts.  hooking -12 to +12 in a circuit would yeild 24 volts...etc.

So again; generally things are negative ground - but always check with a multimeter.

Yes, and your English is considerably better than many of the native speakers who post here. Thanks for that.


8 years ago

Yep, that will work, done it myself. So long as your appliances can be powered by the five volts carried by the USB, that will work.

And don't overload the usb port on the computer.