is 0V always 0V?

phase · Post by **phase** » Mon Sep 22, 2003 4:38 am

Hi!

Im trying to make a stand for my MX222 with a single (multicore) wire trailing to the back of the PC. I was wondering if i could cut down on the number needed by attaching all the 0V wires together inside the pc

That is:

1 x USB, 2 x Molex, 3x GPO etc....

any ideas if this would work, i feel it should do, but just wanted some input!

thanks,

RoB

Paradigm · Post by **Paradigm** » Mon Sep 22, 2003 10:17 am

As long as you take some precautions, they can be tied together. Here is a list of all the connectors on the MX/LK20x-24 series (IN NO PARTICULAR ORDER! Check the manual for pinout orders):

USB
-------
+5 <--- Not needed if the molex provides this
D+
D-
Gnd <-- Can be common

Molex
----------
+5 <--- Not needed if the USB provides this
Gnd <-- Can be common
Gnd <-- Can be common
+12

GPOs
---------
+V (either +5 or +12)
Gnd <-- Can be common
Tach <-- Not needed if you don't want RPM sensing

1-Wire
----------
+5 <-- Not needed (as long as the molex or USB provides +5)
Gnd <-- Can be common
Sdata

Just make sure that the all the grounds are connected together on each end. As for the +5 supply, only the USB or the molex needs to be provided.

I would SERIOUSLY keep the cable length down. 2m (6ft) would be pushing it. If you get into long cable (that isn't properly terminated) you stand a chance of getting singal reflections and crosstalk. Both of which can lead to corrupt communication between the PC and the display. It "should" work, but I can't promise it.

As always be very careful when you start wiring pins together. One misstep and you could fry your PC and LCD.

phase · Post by **phase** » Tue Sep 23, 2003 2:11 pm

Thanks a lot! Thats really helpful!

RoB

Paradigm · Post by **Paradigm** » Tue Sep 23, 2003 6:17 pm

No problem. That's what we're here for.

Shawn Tartaglia · Post by **Shawn Tartaglia** » Wed Oct 01, 2003 3:44 pm

I just wanted to add that while connecting GND (0V) together as instructed in this situation is fine. 0V is not always 0V and sometimes they cannot be connected together.

In some systems different GNDs are isolated for noise. And in some cases GNDs should be separate unless the gauge of wire used is also increased to handle the AMP draw on a single return.

Just thought I would add that so it does not bite ya in the butt later.

phase · Post by **phase** » Wed Dec 10, 2003 9:25 am

hello again,

could you please confirm something for me,

If i am only using all the GPOs to control LEDs do i need the 12V supply rail or just the 5V from the Molex?

Im thinking i dont but just wanted to make sure!

Thanks again,

Rob Stanley

Miles · Post by **Miles** » Wed Dec 10, 2003 9:40 am

Hello...

If you wanted you use all the GPO's for low power all that needs to be connected is the USB cable. Next the jumper needs to be moved from the HP position over to the low powered position. One thing that must be considered if you are using GPO's 1 through 3 with LED's, these DO NOT have current limiting resistor and if connected directly without a current limiting resitor than you will damage your LED.

phase · Post by **phase** » Wed Dec 10, 2003 10:11 am

thanks a lot!

thats great!

RoB

Paradigm · Post by **Paradigm** » Wed Dec 10, 2003 10:40 am

Just thought I should throw in my $0.02(CAD)

Our boards are very simple. I didn't see a need for mutliple ground plains when I designed them, so one ground wire (as long as it's fairly solid) should suffice.

And if you over-current the advanced GPOs, you will simply draw current from your power supply. If your only power supply is the USB, then it will cut out when it noticies that you're drawing too much, and Windows will tell you that your device has been shut down.

If your power supply is an external supply, then you stand a good chance of blowing the transistors that turn on and off the advanced GPOs (witch cut out at about 1 amp) and whatever you have attached to the GPOs.

phase · Post by **phase** » Wed Dec 10, 2003 12:22 pm

ahhh..

so does that mean i do only need to connect it to the USB port (its a internal mobo header so should give enough current!) as i want to 6 LEDs in parallel off each advanced GPO (ie 6RBG LEDs each colour on a different fan channel) and have a couple of the low power GPOs with an LED on for mail notification etc?

so effectively 20LEDs (max) + the board running of the 5V from USB, that should be well below 500mA the port can supply shouldnt it!?

If not, can i replace the 5V line from the USb with the 5V line from my PSU, and im damn sure a few LEDs arent gonna make that explode!

thanks in advance,

RoB

is 0V always 0V?

is 0V always 0V?

Just a Quick Note