Dreamcast Controller + IPAC/2 -- How do I wire the GNDs?

[sofakng]

I've been told that I can't hookup my Dreamcast controllers to my arcade controls at the same time my IPAC/2 is plugged in.  So, the solution is to use a DB25 switch.

My only question, is how do I wire the GNDs?  Right now I have the GND on -every- arcade control connected together and one end of the wire is connected to Player 1 GND and the other end is connected to Player 2 GND (on the IPAC).

When I hookup my dreamcast controllers, do I have to completely seperate the GNDs from each other?  (so player 1's GND cannot touch -any- of player 2's GND?)

[DaemonCollector]

a ground is a ground is a ground is a ground...and so on.

I believe you could connect them together, it shouldn't matter.

[Dave_K.]

First, you are correct in the you do NOT want to mix grounds between dreamcast and I-PAC.  But between two dreamcast pads its ok if you share the grounds. 

The only reason why you may want to seperate grounds between hacked pads is if you are using two seperate connectors (like a pair of molex connectors, one for each side).  If you are wiring both player sides to a single db25 connector, then I think thats fine if you chain around a single ground.

Here is a pic of my control panel wiring with two molex connectors.  Both sides use the exact same pinout, each with their own respective ground.  Much cleaner wiring in my opinion.

[spiffyshoes]

The problem with connecting the ground from two PCB's together like that is that if one of them isn't recieving power it will end looking like all of your buttons are being pressed at the same time.  The simplest solution is to inaddition to connecting the grounds together, connect the +5v power cables together too so that both PCB's are recieving power.  That works great as long as you only have one system plugged in at a time but if you plug them both in and power them up then something is going to get fried.  The solution is to either use a toggle switch to select which system is providing the power at any given time or to use diods to restrict the flow of power.

[Dave_K.]

The problem with connecting the ground from two PCB's together like that is that if one of them isn't recieving power it will end looking like all of your buttons are being pressed at the same time.  The simplest solution is to inaddition to connecting the grounds together, connect the +5v power cables together too so that both PCB's are recieving power.  That works great as long as you only have one system plugged in at a time but if you plug them both in and power them up then something is going to get fried.  The solution is to either use a toggle switch to select which system is providing the power at any given time or to use diods to restrict the flow of power.

Woah, I don't know what you are talking about when you say PCB...you mean two hacked DC padsor dreamcast with Ipac?  If you are talking about two hacked dreamcast pcbs, i don't see how one pad wouldn't be getting power assumung both are plugged in to the DC, and the DC is powered on.

[pmc]

The only reason why you may want to seperate grounds between hacked pads is if you are using two seperate connectors (like a pair of molex connectors, one for each side).

[Dave_K.]

The only reason why you may want to seperate grounds between hacked pads is if you are using two seperate connectors (like a pair of molex connectors, one for each side).  If you are wiring both player sides to a single db25 connector, then I think thats fine if you chain around a single ground.

Is this also OK to use a single ground if you have two different brands or models of controllers? I remember reading (here) that the ground is tied together in the DC iteslf so it shouldn't matter, but I thought I'd ask before I go and do it. I only have one ground on my CP and one controller is already working. It's easiest to connect the Player-2 controller ground to the CP which is already tied to the Player-1 controller. Don't want to hurt my DC.

-pmc

This is correct.  But I don't see what the big deal is to run one more wire for P2 ground.  Unless you have both hacked pads wired to a single connector to your control panel (like the DB25 in sofakng's example), it makes more sense to run a second ground for a two connector setup (see my picture).   You don't want two molex connectors with only one side having ground...what if you swap controllers for PS2, you have to remember which pad and connector has the ground.  Make sense?

[spiffyshoes]

PCB stands for Printed Circuit Board which could be anything from the board in a remote controller to a mother board on a computer.  Since he was talking about hooking up an IPAC and a DreamCast controller at the same time I was talking about the PCB's from a DC Pad and an IPAC which are two different systems.  DC Pad plugs into a Dreamcast and an IPAC plugs into a computer two totally different systems which may or maynot both be constantly powered on at the same time.  Using the method I mentioned you wouldn't have to go in and unplug a molex conecter everytime you wanted to switch systems.

[pmc]

Make sense?

Yup. It's just that my CP is already built (for MAME with an IPAC) and uses a single ground. I have a single connector (it's a SCSI ribbon cable) and a single controller already working. So for now, I'll use the single ground for the 2nd DC controller.

Down the road, I agree that two grounds makes sense. I used two pins on the connector for gound so I could create two loops on the CP fairly easily.

Thanks for the clarification.

- pmc