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Betson Imperial Trackball....Where does the Green wire go? <pic>
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Benevolance:

--- Quote ---Earth ground is pretty simple.  Hook everything that is exposed metal but otherwise not power related to it.  This would be things like your coin door, CP hinges, exposed bolts, etc.  This prevents static buildup and also serves a safety purpose of catching any electrical faults inside the cabinet by forcing the exposed metal to be "safe" to the touch.  Ideally you'd run big-honkin wires from each metal part to a single point, but it's also fine to just daisy chain metal chunks one to the next.
--- End quote ---

So, just to paraphrase and see if I'm catching this right: on my cabinet I have a piano hinge that holds the CP top to the CP box. If I were following best practices, I should be running a ground wire from the piano hinge to a grounding spot on my computer? Even though the piano hinge isn't in contact with anything electrical, but because it is exposed metal?

I don't plan to add a ground for the piano hinge, but I'm new to wiring and I'd like to understand.
MonMotha:

--- Quote from: Benevolance on November 04, 2008, 01:40:39 pm ---
--- Quote ---Earth ground is pretty simple.  Hook everything that is exposed metal but otherwise not power related to it.  This would be things like your coin door, CP hinges, exposed bolts, etc.  This prevents static buildup and also serves a safety purpose of catching any electrical faults inside the cabinet by forcing the exposed metal to be "safe" to the touch.  Ideally you'd run big-honkin wires from each metal part to a single point, but it's also fine to just daisy chain metal chunks one to the next.
--- End quote ---

So, just to paraphrase and see if I'm catching this right: on my cabinet I have a piano hinge that holds the CP top to the CP box. If I were following best practices, I should be running a ground wire from the piano hinge to a grounding spot on my computer? Even though the piano hinge isn't in contact with anything electrical, but because it is exposed metal?

I don't plan to add a ground for the piano hinge, but I'm new to wiring and I'd like to understand.

--- End quote ---

Yup.  Both cabinets I own with a hinged panel (Midway MK2 and a Neo Geo candy) in fact have this hinge grounded.  The MK2 grounds it to a giant ground strap that runs the "length" of the cabinet, and the Neo Geo takes it to a central ground point near the power inlet.  Of couse, if it doesn't bother you and isn't causing problems, then there's not a whole lot of reason to obsess over this.


--- Quote from: RandyT on November 04, 2008, 10:46:40 am ---I just tested a regular USB cable, and on my system the GND signal line is tied directly to the CPU chassis (dead short).  IOW, if you are connecting the green wire to the GND of your encoder, then it's most likely going to be fine.
--- End quote ---

For grins, test it with the power supply COMPLETELY disconnected (all mobo power cables, disk drive cables, etc) but the PC still in the case.  The power lines in a PC are pretty beefy, so the connection inside the PSU can easily read as a dead short.  USB is fortunately somewhat immune to ground shifts due to the diffential signalling.

PCs do tend to play fast and loose with the earth/power ground separation, though.  Some hard drives (for example) tie power common to their metal frames.  It doesn't usually cause problems; I was just giving "best practice" advice.  This practice is frequently ignored with no serious consequences, but sometimes it bites, and being careful can rectify eerie problems that are otherwise difficult to diagnose.
RandyT:

--- Quote from: MonMotha on November 04, 2008, 05:53:50 pm ---PCs do tend to play fast and loose with the earth/power ground separation, though.  Some hard drives (for example) tie power common to their metal frames.  It doesn't usually cause problems; I was just giving "best practice" advice.  This practice is frequently ignored with no serious consequences, but sometimes it bites, and being careful can rectify eerie problems that are otherwise difficult to diagnose.

--- End quote ---

I know, and as always, your explanations are a great read and much appreciated.  I just wanted to put people, who may not have it  hooked up "optimally", at ease.  If the grounds are tied together in other parts of the system (as my test pretty much concludes that they are), then as a practical matter, there's little difference in running the separate wire.  If one has some sort of issue with their controls, certainly consider these possibilities.  But there's probably no reason for concern or need to re-wire if everything is working properly.

RandyT
CheffoJeffo:
Just wanted to  :applaud: the explanations given here -- MonMotha's post should be part of a "Wiring Your Cab" article in the wiki.
MonMotha:

--- Quote from: RandyT on November 05, 2008, 12:13:57 pm ---
--- Quote from: MonMotha on November 04, 2008, 05:53:50 pm ---PCs do tend to play fast and loose with the earth/power ground separation, though.  Some hard drives (for example) tie power common to their metal frames.  It doesn't usually cause problems; I was just giving "best practice" advice.  This practice is frequently ignored with no serious consequences, but sometimes it bites, and being careful can rectify eerie problems that are otherwise difficult to diagnose.

--- End quote ---

I know, and as always, your explanations are a great read and much appreciated.  I just wanted to put people, who may not have it  hooked up "optimally", at ease.  If the grounds are tied together in other parts of the system (as my test pretty much concludes that they are), then as a practical matter, there's little difference in running the separate wire.  If one has some sort of issue with their controls, certainly consider these possibilities.  But there's probably no reason for concern or need to re-wire if everything is working properly.

RandyT

--- End quote ---

Heh, didn't mean to imply you were doing anything bad or wrong.  I "violate" those rules all the time (and sometimes pay the price with flaky operation during the winter time...), especially when trying out new stuff and the cabinet wiring is being constantly changed.  I was mostly looking for another data point.  Some PCs will intermix the two all willy nilly and others are pretty good about maintaining the separation, and I was just curious as to which category yours falls in.  Regardless, in all PCs using PC power supplies, DC power common will be tied to earth ground at at least one point: inside the power supply.
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