M2-ATX(-HV) 160 watt Intelligent DC-DC PSU

**Sonicxtacy02** · 07-07-2009, 11:20 AM

I'm using an aluminum case professionally made and it has made a difference but the interference is still there. Its definitely from the power supply too, if i switch PSU's to a house PSU it goes away.

**joshuo** · 07-07-2009, 11:20 AM

how about aluminum tape?

**Sonicxtacy02** · 07-07-2009, 11:22 AM

Originally Posted by rickd

As I said before, I do not get RFI from the computer. But I did use an all-metal enclosure that is grounded.

when you say your case is grounded what specifically do you mean. You've run a wire from your case to the same ground as your power supply? I've tried this but it made no difference in any of my 6 carputer setups. This RFI issue is really the LAST issue i have before i have a perfect CarPC in my mind

**joshuo** · 07-07-2009, 11:25 AM

Have you tried grounding the case, PSU, MB, TS, and the Radio to the same ground?

**rickd** · 07-07-2009, 03:24 PM

Originally Posted by Sonicxtacy02

when you say your case is grounded what specifically do you mean. You've run a wire from your case to the same ground as your power supply? I've tried this but it made no difference in any of my 6 carputer setups. This RFI issue is really the LAST issue i have before i have a perfect CarPC in my mind

Grounding a big issue, and cars these days have a careful grounding plan. Ground loops can play hell with sensors for engine management computers.

Grounding for RFI is different, though. Effectively grounding for RFI requires a very low impedance ground path. Running a little wire from the case to the body may not be good enough. My case is grounded to the main ground point on the vehicle through 10-gauge wire, which is still marginal from an RFI point of view. But it's the best I can do. For ham radio equipment in my home, I use copper flashing as a ground conductor.

More importantly is the ground on the receive antenna for the radio receiving the RFI from the computer. The shield and the ground plane of the antenna should be grounded very carefully with a very low impedance ground conductor. A 10-gauge wire to the negative lead on the battery sounds about right. That will help shunt to ground any coupled signals reaching the shield on the radio antenna.

RickD.

**rickd** · 07-07-2009, 03:29 PM

Originally Posted by joshuo

The engine def. puts out tons of RFI, that's another reason why firewalls in cars are metal.
Just think of the amount of metal that spins at 1000's of RPMs and all the metal on metal rubbing... Add a turbo and it gets even worse.

another thought on shielding:
It could be as simple as covering the computer box with some sheet aluminum or even metallic paint?

Metallic paint? No. The case needs to have very low impendance. Think sheet metal, not a molecule-thick coating of metal on a piece of plastic, and definitely not metal particles that are effectively insulated from each other by the paint binder.

It isn't the spinning metal that makes the RFI, unless the metal is somehow magnetized (which you hope is not the case). It's the ignition system. Diesel engines are RF quiet--they have no ignition systems or spark plugs. That 20,000-volt spark plug, running through an inductive spiral-wound plug wire, makes a pretty effect spark-gap transmitter.

The alternator uses solid-state components to regulate voltage, and the switching of those components can also spray RFI.

Rick "thinking the shield on the radio antenna coax is the place to start" Denney

**Sonicxtacy02** · 07-07-2009, 03:33 PM

i always heard it was bad practice to ground directly to the battery. Would a high gauge (4-8Ga.) wire run directly to the battery then split via distribution block to all computer components be advised. Right now my radios ground is not my computers ground because the ground would then have to travel the distance of the car. I've heard that ground wires need to be short even in high gauge

**joshuo** · 07-07-2009, 04:16 PM

^ get 10 ft of 10 or 8 gauge wire at a hardware store, and test it. just hold it to your PC ground and then to the neg battery terminal....

Doesn't hurt to try...

**fatejd** · 07-08-2009, 01:54 PM

I just upgraded my car pc and now I can't get power from my M2-ATX, at least I think that's the problem. I turn on the ignition and get the green standby light on my mobo and the dim HDD activity light on my case (my power light is not hooked up). Nothing else starts up: HDD, fans, monitor, etc. Could this be the polarity problem on the J8/J9 jumpers? Also, I looked through this thread and didn't see which pin is live and which is ground on these jumpers - did anyone figure it out?

Thanks

**Sonicxtacy02** · 07-08-2009, 02:21 PM

Originally Posted by joshuo

^ get 10 ft of 10 or 8 gauge wire at a hardware store, and test it. just hold it to your PC ground and then to the neg battery terminal....

Doesn't hurt to try...

Just bought 20 feet of 8awg silver wire at parts express for 0.59/ft. Thanks for the suggestion

I just hope it works when it arrives.

Originally Posted by fatejd

I just upgraded my car pc and now I can't get power from my M2-ATX, at least I think that's the problem. I turn on the ignition and get the green standby light on my mobo and the dim HDD activity light on my case (my power light is not hooked up). Nothing else starts up: HDD, fans, monitor, etc. Could this be the polarity problem on the J8/J9 jumpers? Also, I looked through this thread and didn't see which pin is live and which is ground on these jumpers - did anyone figure it out?

Thanks

just take the jumper off of the motherboard and short the pins together to see if the fans spin and it boots. That will tell you if its the jumper or something else.