FAQ: How to Wire an OPUS PSU - Page 5

WoLLy · 04-19-2006, 05:43 PM

I am about to hook up my dsatx into my mr2 which already has an amplifier installed. I'm trying to make this install as easy on myself as possible.

Instead of running 4 gauge wire to a power distribution block and then sending it to the amp and DSATX, would it be possible to just run another 8 gauge wire and fuse from the battery to the DSATX and ground the dsatx with a separate wire in the same place the Amplifier ground is at?

Quattro · 04-20-2006, 12:32 AM

yes, you could do that, but since your gonna run a new wire anyways why not do it the proper way? unless you have extra 8awg wire laying around.

lfndust · 04-20-2006, 12:38 AM

I know in GM cars, any "Pink" wire is an acc power wire so you can use that instead of your ignition wire. Thats my $0.02 Thanks for the great info though!!!

WoLLy · 04-20-2006, 08:15 AM

Quote: Originally Posted by Quattro

yes, you could do that, but since your gonna run a new wire anyways why not do it the proper way? unless you have extra 8awg wire laying around.

I don't really want to buy a power and a ground distribution block. Sounds expensive.

Quattro · 04-21-2006, 12:49 AM

Quote: Originally Posted by WoLLy

I don't really want to buy a power and a ground distribution block. Sounds expensive.

umm, it'll be cheaper then the wire. they'll both be what, around $20 total.

WoLLy · 04-21-2006, 08:48 AM

hrmm, for that kind of money i'll just buy the block, good idea.

01black_ac · 04-28-2006, 06:35 PM

Quote: Originally Posted by Pepe

http://www.rbeelectronics.com/wtable.htm
(Third chart down)

These values are just recommendations, as you'll find lots of charts like that all over the net with different recommendations, but I've found this one to be the best IMO. But I always choose wire at least one gauge larger than what it shows, then select a fuse that's more than the current value your going to be drawing and at or below the rating of the wire.

So for example, if your computer is going to be pulling an average of 20A
@12V over a length of 20' of wire, the recommended gauge is 12. I would then use 10 gauge (slide down to the next lower gauge on that chart under your length), and add a 30A fuse.

Sure there will be people that say "I've ran this and this off that gauge wire for years with no problem...", but a little extra resistance in the wire can make a big difference, resulting in the possibility of your wiring catching fire.

Okay, so I guess I'm still not entirely clear on something. I see from the chart you linked where you would get 12AWG wire over 20' when drawing 20Amps, and I understand dropping to a slightly heavier AWG just for a little added buffer... But why the 30Amp fuse if you've already stated the system will be drawing only 20Amps...? Isn't it safer to have the fuse as close in Amps to what you're actually going to be drawing as possible?

For example, I'm going to use 8AWG wire over about 15' to power my Opus 120 (120Watt PSU). (I realize 8AWG is overkill for a 120W PSU, but I wanted the ability to add future devices later without having to run a new cable.) The Opus has an onboard 15Amp fuse, but its max draw is 10Amps... So wouldn't I want to use a 10Amp fuse on the 8AWG wire next to the battery? Or is it because the heat at 10AMPs will never come close to burning an 8AWG wire, so going higher than 10AMP fuse is perfectly safe?

I'm also going through a distro block once the 8AWG reaches the trunk. I was planning to load the distro block with a 10AMP fuse as well, but maybe I'm not calculating that correctly?

'01

Pepe · 05-05-2006, 11:55 AM

Quote: Originally Posted by 01black_ac

For example, I'm going to use 8AWG wire over about 15' to power my Opus 120 (120Watt PSU). (I realize 8AWG is overkill for a 120W PSU, but I wanted the ability to add future devices later without having to run a new cable.) The Opus has an onboard 15Amp fuse, but its max draw is 10Amps... So wouldn't I want to use a 10Amp fuse on the 8AWG wire next to the battery? Or is it because the heat at 10AMPs will never come close to burning an 8AWG wire, so going higher than 10AMP fuse is perfectly safe?

I'm also going through a distro block once the 8AWG reaches the trunk. I was planning to load the distro block with a 10AMP fuse as well, but maybe I'm not calculating that correctly?

'01

Your Opus is already fused, so that's not a problem. The reason your adding another fuse is to protect the wiring. If your wiring shorts out 2" before getting to your Opus, it could start a fire. Your 8 gauge wire has a much higher amperage rating that what your Opus is going to pull, so you do have a lot of lee-way (sp?) there for the size of your fuse. Anywhere between 15 and 30 amps would be fine. I just wouldn't use a fuse that's exactly the same size as your Opus max rating. Give it a little bit of freedom. If Opus puts the fuse higher than it's max rating right from the factory, that there's no reason why you shouldn't do the same.

01black_ac · 05-05-2006, 08:39 PM

Okay, thanks for that info... I think I'll end up going with a 20Amp fuse near the battery. Now I'm thinking I might want to put higher Amp fuses in my distribution block, since I was planning on using 10Amp fuses in there. I suppose I could run it with 10's in the distro block for a few days and see if they blow out, then switch to 15's...

'01

Mikomi · 08-05-2006, 10:48 PM

Wow, nice this clears things out (==> pictures) !
i only dont understand the ign thing, the one side is connected to the
power supply and the other to ? according to the sceme it's connected
to the positive (red) wire ? but according to to sceme with pictures it's connected to something else but it's not realy clear to me to what.
pictures make it easy for ppl to understand (especialy ppl like me who don't know anything about electronics and still realy want a carpc)
thnx

Quote: Originally Posted by Quattro

2) Run the IGN wire to the Opus as well. For this you can either tap into a fuse for the ignition switch of the car.

Quattro · 08-06-2006, 12:05 AM

You can connect the IGN wire to either the ignition switch or a fuse or anything that recieves power once the key is turn to the on position. You can connect it to your stock headunit as well, you'll just have to check the pinout and figure out which one get power to it when the key is turn.

jollyeskimo · 08-17-2006, 10:51 PM

note: This is meant as an addendum to Bugbyte's Powering your Car PC when it's not in the car post.

Basically this is how I connect a spare desktop power supply to my opus for testing standby/hibernation/startup while not hooked up to the car.

Just make sure the power supply is up to the job, and that the power supply is turned on (green/PS_ON lead on ATX connector (pin 14) shorted to any black/ground).

Close the switch to simulate an "ignition on" in the car, and open the switch to simulate an "ignition off" in the car, which will start the delayed shutdown/hibernate/standby.

I don't know the pinout of the power input connector on other opus psu's, so you might have to rewire appropriately for your model.

also, for OPUS ITX MINI case owners, make sure to screw in the top cover before powering on the system. The power supply is grounded to the top cover, and unless the cover is screwed in an connected to the other piece (that the motherboard is grounded to), it can be a cause for problems like not POSTing and giving you a Bad Power Supply beep code.

Quattro · 08-18-2006, 12:32 AM

good job I added it to the first post.

DodgeCummins · 08-19-2006, 06:56 AM

This is a very good FAQ.

FUSES. You want to always fuse as close to the battery as possible...and as close to the power you plan on pulling without going too far over. Why? Obviously if it is unfused or has a ridiculously sized fuse then a direct short will turn your battery/wire into a light bulb for a while until the engine bay catches fire.

If you have a fuse too large, your cabling will be OK, but if you have a malfunction on the board, that circuit board will now become the source of fire...and you will get a fire in your dashboard.

You want the fuse to blow EXACTLY when it is needed...and not so early that it blows every other day.

The OPUS 120 has a built in 15A fuse right at the power entry...there is no need to put a larger fuse on the line from the Battery to the board.

DISTRIBUTION BLOCKS...for audio equipment...if you have them hooked to different grounds (due to using the vehicle chassis as the wiring) you can get the problem known as Ground Loop. The symptoms are noise/hum in your speakers. The best answer would be to run some nice welding cable to your amp racks from the negative battery terminal and use a giant distribution block to feed ALL your components from...no you don't need a fuse because if the grounding wire touches the chassis...there is no voltage potential...so no problem (the are the same electrically)

I have all my amps running from the same chassis ground, and everything else from separate grounds...I run no filters, and have no noise in the stereo...(however I do get computer noise in my ham radio...but that is a different story)

DarquePervert · 08-26-2006, 12:38 PM

This FAQ is so good that the newbies are postin their wiring questions in it.
For this reason I'm closing this FAQ thread.

We really do ned to make the FAQ Emporium a moderated forum.