Ground (static relief) wires on Happ Trackball

[electricd]

I finally got my Happ trackball connected to my Optipac tonight, and ended up not using the green ground wires that are used to release static electricity.  The ball/optipac works great, but my question is has anyone used a trackball like this long term without the green grounds hooked to anything?  Am I just asking for trouble, and if so what should I connect them to?  My control panel is completly made of wood, so no convenient grounding points asside from the ones going to the optipac.  Thanks in advance.

ED7

[liche]

The Ground wires serve much more purpose than anti-static.  The primary reason you ground everything (especially in a cabinet like a MAME cabinet) is for safety reasons.  

For example, if your monitor frame wasn't grounded and there was a short between 120VAC and the monitor frame, this can pose a electrical shock hazard to the user as the monitor frame will now be energized.  Same thing with other controls.

Also, even though some controls will have their own +12VDC and +12VDC RTN lines, grounding may be necessary for proper operation.  (See Sound and Car Amp post) for more information regarding this.

In your case, the ground is primarily used for safety (especially if there are metal components) and for anti-static purposes.

A rolling plastic ball and build up a lot of static charge (up to 50-100kV) which can damage both the electronics on board the roller and the computer it is connected to as well.

So it is VERY IMPORTANT to make sure that GROUND lead is attached ! ! ! !

[electricd]

Liche,

Thanks for the reply, but maybe you didnt understand my post.  The electronics for the X and Y axis boards both have thier own ground leads which I have hooked up.  The ball is functioning correctly with the component board ground leads hooked up, but if I hook up the static relief ground leads, do I hook them then just to the same ground point I have the electronics grounded to?

ED7

[BobA]

I would suggest using a earth ground such as the ground that the ground plug on a 3 prong electrical plug is connected to.  This is often refered to as a chassis ground but be careful here as arcade monitor chasis are often hot rather then true grounds.  Do you have an electrical distribution strip for your 120 VAC with the earth ground connection?

If it was meant to tie into the logic ground I do not think that they would have supplied the separate green wire for the protective ground.

BobA

[electricd]

There is no distribution strip, as this is a custom cabinet.  I just have all of my components plugged into a power supply.  Thanks in advance.

ED7

[Elkor]

connect it to the metal chassis of the powersupply, that is usually tied to earth ground through the plug.

-C

[liche]

Actually you have to be careful what you call grounds.  The grounds you are referring to for your control circuit are more correctly your power supply returns for your control circuit.  It is very bad to use these types of "grounds" for chassis ground.

The best method for grounding all equipment in your cabinet is the following:

1.  Install a 1/4" bolt through the bottom of your MAME cabinet so that it installs through the cabinet from the bottom.  Attach a lug from this bolt to your incoming GROUND from your 120VAC power.

2.  Next, any equipment you need to ground, simply attach a lugged ground wire and attach to the equipment and then back to this "main" ground stud.

So to get back to the original question, you shouldn't use your power supply return (ground) of your control circuitry as an ESD protection ground.  

If static built up enough on the roller ball and discharged to either the control positive line or the control ground line, it is powerful enough to possibly damage any control circuitry you may have.

Remember, that roller ball could charge up to almost 100kV.  Very high peak transient current surges can develop from that discharge into sensitive TLL and more so CMOS chips and cause permanent damage.

[electricd]

Ok that makes sense.  So If I attach the 3rd prong from my incoming AC to a lug through the bottom of the cabient, and then ground my trackballs "chasis ground" wires to it, then that should work right?  If this is the case, I will get it done today.  Thanks.

ED7

[liche]

>>Ok that makes sense.  So If I attach the 3rd prong from my incoming AC to a lug through the bottom of the cabient, and then ground my trackballs "chasis ground" wires to it, then that should work right?  If this is the case, I will get it done today.  Thanks.

Correct.  But you also don't want to modify that cord - you need that 3rd prong to make grounding connections to other devices powered on your power strip.

I use a standard industrial power cord and then terminate my ground wire (green) to a large 1/4" ground stud, and then the hot (black) and neutral (white) power wires to a large screw terminal strip in the bottom of the cabinet.  Then each device is wired off the terminal strip via ring lugs.

[electricd]

I actually have my cord terminated inside a regular wall jack box in the cabinet already.  Would be pretty easy to extend the ground from that box to an external grouding pole through the base of the cabinet.  Thanks for the help!

ED7

[atog]

I don't have my happ trackball ground connected to anything either, and my cabinet has been working perfectly for the 4 months that is has been in existence.

[liche]

Seeing the last four months were summer months (if you live in the northern hemisphere), static electric build-up isn't really much an issue as humidity is relatively high and is at a high enough level to dissipate any static build-up.

However, the winter months are approaching and this is when static electricity is at its worst.  Your homes heaters are working full tilt, the winter air is very dry, and moisture is low.  

On another note, its the best time to fire up those wimherst and van de graaf machines ! ! ! !

[Tiger-Heli]

Somewhat OT, but I was planning to mount a trackball in a plastic Radio Shack project box and use a USB mouse hack to connect it to the PC.  How would all this grounding stuff work for this set-up.

Also, Atari and the PS2 both sold plug-in T-balls for their console systems and I would think they would have these same problems.  How did they handle it?

[liche]

Its not too serious to really worry about (especially if making your own.)  Its like putting a lightning rod on your house.  Just because you do it doesn't mean lightning is really going to strike.

However, if you do plan on building your trackball in a metal frame, then you should definitely be grounding that frame for safety purposes, especially if you have exposed 120VAC in your cabinet.