My New Wiring Diagram: Could I get some feedback?

**azzurro** · 12-10-2005, 12:32 PM

I currently have my car pc up and running great. There's a couple of changes that I want to make.

First, here's my old diagram. My current setup is just like this, only there are two diodes at each of the the wires going to the Opus Ignition, so that if the 2nd switch is closed (the one coming from the distro block, i.e. directly from the battery) and the 1st switch is closed is as well, this does not end up feeding the car's ACC line.

Fused D. Block is a fused distribution block. The 25W PSU gives out a regulated 12V for the Xenarc 700TS. The computer and sound card (which needs 5V) are in the trunk. The power supply for the Xenarc is up in the front of the car.

The relay is there to only allow the amp to turn on once the PC is on (to avoid a "boom" noise).

OK, now for the changes I've made. First of all, ignore the 2nd battery. I need to do more research into this. Just pretend that the Opus power is wired to the distribution block, like in the first setup.

What I want to do is tie the Xenarc's power to the computer's. This is so I don't need to do this Xenarc mod. Will this work as I want it to?

Also, the reason that I have two mini relays is because my current relay is rated only at 1 amp. Now, the remote lines don't draw much, but if I fed this output (i.e. pin 30) directly to the input of the Xenarc's power supply, we might be pushing more than 1 amp. Is this correct? Or should I just buy a mini relay that can do more than 1 amp?

The diagram:

Some other questions: The black wires on the molex connector... should I ground these, or is the PC and the Opus' grounds sufficient?

Also, When running 5V to the front of the car (to power hubs and such), should I run the ground cable from the molex as well, or just ground the hub to the chassis? If I ran the ground line, that would cause a ground loop issue, correct? I already have powered hubs in the front of the car, grounded to the chassis, but since I'm redoing the wiring I just want to make sure that I did this right.

Any help appreciated!

**Alanh** · 12-10-2005, 08:17 PM

Are you deliberately avoiding powering the Xenarc directly from the Opus +12 output? Someone correct me if I'm wrong, but I think a lot of people here power their displays directly from the Opus. You could avoid the relays and your second power supply if you did that unless you're short on computer power. I don't know if the mod changes things since I don't have a touchscreen.

I wouldn't use two relays for the Xenarc power supply if you keep it. The standard Bosch automotive relays that are roughly square in shape are rated for a lot more than the 2+ A the 25W supply needs (20A or 30A if I remember right), so I'd get one of those. They're not too expensive and would make the whole setup that much simpler.

As for the grounding, what you really want to avoid is multiple ground paths, so if you have stuff grounded to the chassis and leave those connected, and then add another direct ground, you might get ground loops. AFAIK, you'd be best to go one way or the other. I'd get a second opionion or two though, since I haven't actually done what you're doing.

If and when you get around to adding a 2nd battery as shown, you'll want a pretty beefy relay there. The charging current could be quite large, depending on the size and type of battery and how much it has been discharged. The standard Bosch relays won't be up to the task if its a full-size battery. Do a search for battery isolators - you'll find a lot more information than you probably want to wade through on that topic.

**azzurro** · 12-11-2005, 03:09 PM

Originally Posted by Alanh

Are you deliberately avoiding powering the Xenarc directly from the Opus +12 output? Someone correct me if I'm wrong, but I think a lot of people here power their displays directly from the Opus. You could avoid the relays and your second power supply if you did that unless you're short on computer power. I don't know if the mod changes things since I don't have a touchscreen.

I wouldn't use two relays for the Xenarc power supply if you keep it. The standard Bosch automotive relays that are roughly square in shape are rated for a lot more than the 2+ A the 25W supply needs (20A or 30A if I remember right), so I'd get one of those. They're not too expensive and would make the whole setup that much simpler.

I'm running a power-hungry Celeron D, so I don't want to push the Opus harder than I have to. I'm already using the other power supply and it's working great.

I just want to fix the issue of the USB connection not syncing with Windows. There is that mod that I referenced earlier, but I think that if I use the relay it will fix the issue. Are the people that are powering the Xenarc directly from the Opus experiencing these USB issues?

In terms of the relay: That is not a Bosch relay that I'm using. It's a mini-relay. I have to check what it's rated at, but I believe that it is 1 amp. I think I may just try and find a mini-relay that's rated at about 2 amps. Actually, if I got rid of the second relay, I'm sure the single relay would still be fine, but I would definitely be near the 1 amp mark. It would be nice to use a slightly bigger relay in case I need to add another power supply, to take care of 5V.

Are there any drawbacks of using a Bosch relay when you only need an amp or two?

Originally Posted by Alanh

As for the grounding, what you really want to avoid is multiple ground paths, so if you have stuff grounded to the chassis and leave those connected, and then add another direct ground, you might get ground loops. AFAIK, you'd be best to go one way or the other. I'd get a second opionion or two though, since I haven't actually done what you're doing.

Grounding has me confused.

My audio amps and the Opus are grounded to the same spot, a bolt behind the rear passenger seat.

My Audigy 2 NX is grounded via the black wire on the molex connector.

My USB hubs in the front of the car are grounded via the black wire on the molex connector.

The second power supply (for the Xenarc) is located in the front of the car, and is grounded to chassis.

I don't remember how I grounded pin 86 on my relay.

About this molex connector business: Power is coming from the power supply, which is grounded to the chassis. Should I also ground the ground wires from the molex to that same spot?

Should I have grounded the Xenarc PSU from the ground on the molex connector?

Where should I ground the relay?

I understand that using different grounding points will cause a grounding loop, but can't the same be said of running loooong ground wires?

One thing to note that may or may not be relevant or linked: My Audigy actually died one day, back a couple of months ago. It just won't turn on. Molex connector is still giving power, and I tried the AC-DC adaptor, which is also still working fine.

Originally Posted by Alanh

If and when you get around to adding a 2nd battery as shown, you'll want a pretty beefy relay there. The charging current could be quite large, depending on the size and type of battery and how much it has been discharged. The standard Bosch relays won't be up to the task if its a full-size battery. Do a search for battery isolators - you'll find a lot more information than you probably want to wade through on that topic.

Thanks! I haven't done enough research yet, that's why I said to ignore the second battery. The way it is now would probably cause a fire or toxic chemicals to be released into the air