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Can A 12v Line Share A Ground With The 5v Line?


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#1 JEB-101

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Posted 04 May 2005 - 08:29 PM

I'm makig a LED ring and vents... And taking the power from molex... but my question is... I have 2 different power sources. 12V is the LED ring... and 5V is the side vents.. (im low on selection of resistors...lol) but I'm wondering if I could use the same ground?

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#2 SpookieStylez

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Posted 04 May 2005 - 08:31 PM

yup
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sS

#3 JEB-101

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Posted 04 May 2005 - 08:32 PM

thanks man... my browser didint even have time to refresh.. lmao..

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#4 SpookieStylez

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Posted 04 May 2005 - 08:35 PM

no problem biggrin.gif
i just hit the *go* button after my last post and this thread was sittin on top
plus it was a quick answer
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#5 lostboyz

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Posted 04 May 2005 - 09:15 PM

you have to use a 12v ground i believe, if you have a 12v lead going to a 5v ground you will have 7v running through the 12v cable

if you ground everything to a 12v ground or the case you should be fine

please correct me if im wrong

#6 DuckOfDeath

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Posted 04 May 2005 - 10:54 PM

QUOTE(lostboyz @ May 4 2005, 01:21 PM)
you have to use a 12v ground i believe, if you have a 12v lead going to a 5v ground you will have 7v running through the 12v cable

if you ground everything to a 12v ground or the case you should be fine

please correct me if im wrong

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You're wrong....

He's not talking about using the 5v cable as the ground comming out of his 12v leds. He's talking about using the same ground cable. There's a reason it's called common ground: it's common. smile.gif

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#7 JEB-101

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Posted 04 May 2005 - 10:57 PM

QUOTE(DuckOfDeath @ May 4 2005, 06:00 PM)
You're wrong....

He's not talking about using the 5v cable as the ground comming out of his 12v leds.  He's talking about using the same ground cable.  There's a reason it's called common ground: it's common.  smile.gif

-Duck!

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ok cool... I did it raight after Ss answered... It works great... 16 round the jewel and 10 on the vents biggrin.gif all I need to do now is put in the switch and find a spot for all the wires...lol

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#8 T.J.E.

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Posted 05 May 2005 - 12:40 AM

QUOTE(DuckOfDeath @ May 4 2005, 10:00 PM)
You're wrong....

He's not talking about using the 5v cable as the ground comming out of his 12v leds.  He's talking about using the same ground cable.  There's a reason it's called common ground: it's common.  smile.gif

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mmm...i think he ment the 5v ground wire and the 12v ground wire...but maybe they are common ground i dunno....but running the 12v ground thru the 5v ground and it turning to 7v makes a biut of sense...i just used the 12v ground for my 12v fan ground, and the 5v for my LEDs

#9 DuckOfDeath

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Posted 05 May 2005 - 03:41 AM

QUOTE(T.J.E. @ May 4 2005, 04:46 PM)
mmm...i think he ment the 5v ground wire and the 12v ground wire...but maybe they are common ground i dunno....but running the 12v ground thru the 5v ground and it turning to 7v makes a biut of sense...i just used the 12v ground for my 12v fan ground, and the 5v for my LEDs

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Gound is ground, no matter where it is. There is no such thing as "12v ground," it just doesn't make sense. Voltage is a measurement of potential. 12v means 12v with respect to ground, just as 5v means 5v with respect to ground. 12v ground means absoultely nothing, other than maybe a short, some sparks, and some non-functioning equipment.

If you take the positive end of your leds and connect them to the 12v wire comming out of the molex, and then connect the negitive end to the 5v wire comming out of the molex, you will have droped 7v worth of potential. I.E, you will have 7v running through the leds. Think of it as a staircase:

CODE


12v
------------|
              |
              |
              |
              |
              |     5v
               ------------|
                              |
                              |
                              |
                              |   Ground
-----------------------------------------


If you go from 12v to 5v, you've gone down 7 steps, or 7v. But, look, ground is always, um, on the ground.... smile.gif

The only reason there are two grounds going into the molex connector is to make sure that the current returned to ground does not become too great for the cable to handle. The amount of current you're running through your leds is negligible compaired to the amount of current say, a hard drive consumes.

-Duck
Edit: grammar

Edited by DuckOfDeath, 05 May 2005 - 03:43 AM.


#10 T.J.E.

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Posted 05 May 2005 - 03:47 AM

ok...well...i guess the guy italked to lied...anyways....i guess you learn new things everyday..thats twice somone has made me feeel stuipid today lol...o well....i am stuipid i guess...tongue.gif......but i know now, so i shouldn`t make the mistake of telling somone 'you have to use the ground next to the 5v or it will short or wreck somthing...'



#11 DuckOfDeath

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Posted 05 May 2005 - 04:18 AM

QUOTE(T.J.E. @ May 4 2005, 07:53 PM)
ok...well...i guess the guy italked to lied...anyways....i guess you learn new things everyday..thats twice somone has made me feeel stuipid today lol...o well....i am stuipid i guess...tongue.gif......but i know now, so i shouldn`t make the mistake of telling somone 'you have to use the ground next to the 5v or it will short or wreck somthing...'

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I had no intentions of making you feel or look stupid... I just wanted the correct information out there. Hell, the 5 years of hell (Electrical Engineering courses) I took in college should be put to use sometime. wink.gif

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