CarPC, audio\interference issue.

iNcArCeRaTiOn · 07-26-2007, 12:20 AM

I've got my carpc up and running now, and now it's time to work out the bugs. =]

so, the first thing i notice when i turn it on for the first time is there's an annoying interferance noise coming from my sound system (i have it hooked up to my head-unit directly from the audio out of the carpc). it's a humming noise, and according to the RPMs i will get either none or a lot of kind of louder (than the humming) constant high pitch squeeling noise. i can also hear my engine louder, it's like there's a microphone in the engine compartment next to a certain part or something.

it's not the connection to the car either cause i hooked up my Pro-97 Scanner and it sounded crystal clear, it's like something's not grounding properly or something.

then my other problem with interferance is my LCD touch screen is having like waves like a tube television would have when there's a HUGE speaker next to it or something. it's not the screen cause i've had it hooked up to another computer and worked great.

any ideas\suggestions\comments appreciated =]

i love it though, it'll be great once i get rid of the kinks, i'm using RR with digitalFX skin

scott_fx · 07-26-2007, 12:43 AM

Quote: Originally Posted by iNcArCeRaTiOn

I've got my carpc up and running now, and now it's time to work out the bugs. =]

so, the first thing i notice when i turn it on for the first time is there's an annoying interferance noise coming from my sound system (i have it hooked up to my head-unit directly from the audio out of the carpc). it's a humming noise, and according to the RPMs i will get either none or a lot of kind of louder (than the humming) constant high pitch squeeling noise. i can also hear my engine louder, it's like there's a microphone in the engine compartment next to a certain part or something.

it's not the connection to the car either cause i hooked up my Pro-97 Scanner and it sounded crystal clear, it's like something's not grounding properly or something.

thats probably exactly what it is... a ground loop. make sure the spot you ground the psu to is clean and bare metal. also try to limit the amount grounding points you have. all amps, pc's and anything else should be ground at the same point.

Quote: Originally Posted by iNcArCeRaTiOn

then my other problem with interferance is my LCD touch screen is having like waves like a tube television would have when there's a HUGE speaker next to it or something. it's not the screen cause i've had it hooked up to another computer and worked great.

any ideas\suggestions\comments appreciated =]

i love it though, it'll be great once i get rid of the kinks, i'm using RR with digitalFX skin

the rippling is a power issue. you may want to tap of your psu if you have the juice on the 12 volt line or you could also buy a point of load psu as a dedicated clean 12volt power source. but first check out the ground. are you running it off of the cig lighter socket?

iNcArCeRaTiOn · 07-26-2007, 02:25 AM

yeah it's off the cig lighter socket (the screen)

as far as the PSU in the PC, i have the VoomPC (not II) and it's just up on the pegs screwed down with 2 screws...

thx for replies so quickly

scott_fx · 07-26-2007, 02:48 AM

you know, i always wondered if adding a cap in line with the screen power leads would help solve the scrolling.

the psu has a neg, pos, and acc lead that you wire into. check the ground on that lead

durwood · 07-26-2007, 09:42 AM

If it's picking up the nosie on the video cable, you might want to install a ferrite close to the screen on the vga cable. Otherwise, a clean power supply should help. What screen are you using? Liliputs usually come with an egg shaped regulator on the power lines.

You might want to look around or search in the LCD section, I think people have discussed ways of fixing it before. I wonder too if a small cap connected across the power lines to the screen would help smooth it out or not. Dunno?

iNcArCeRaTiOn · 07-29-2007, 10:17 PM

i had the PSU wired up by some friend at bestbuy in the mobile install bay, so i'm not sure what he connected those too, i'll have to ask him about that but the audio is really bugging me.

i checked the PSU it's screwed onto the little pegs and not touching anything else neither is the motherboard i put something under it so it doesn't touch the case below it.

it has to be something with the mini-itx PSU though cause if i hook it up inside the house with a normal ATX PSU and hook the speakers up it sounds crystal clear. what else would it be? should i get rubber washers between the PCB board of PSU and the pegs or something?

should i have the guy change the wires to what they're connected to as far as the power feeds?

i've tried a different audio cable too just seeing if it was something simple, same thing.

thanks

scott_fx · 07-30-2007, 01:34 AM

did you check the grounds yet? i'm not talking about how the psu is mounted but how it is grounded

iNcArCeRaTiOn · 07-30-2007, 02:04 AM

nope, like i said i'm not sure where or what he grounded it too, i'm gonna ask within a few days when i see him at work. then i'll get back with you\you guys here.. =]

scott_fx · 07-30-2007, 02:39 AM

ok, i'd put money on it that it's a grounding issue

pancit175 · 07-30-2007, 05:22 PM

Just to chime in, If you want to eliminate the waves on the screen, another option you can do is to get +12V from the power supply. Given that your PSU can handle the extra current. I believe that the cig lighter wires is more prone to noise. And it is possible for the noise from the screen can be picked up through the motherboard to your audio output. Another reason why I like optical. I wont bore you with that though.

iNcArCeRaTiOn · 08-04-2007, 02:24 AM

haven't gotten a chance to get the guy that did the install to look at it again but i was playing a CD today and i noticed it was also (the interferance noise) there when playing a CD... what can it be? does this help at all or confuse even more?

thanks

iNcArCeRaTiOn · 08-04-2007, 11:35 PM

well, good news. i tried a test run inside the car with everything attached EXCEPT the power method being powered by the vehicle and i ran it off a standard ATX PSU connected to a normal wall outlet and i still could hear the sound but it was like a 1\3 as bad as was it before. so out of curiosity i unplugged the VGA cable from the back of the computer got better, so i unplugged the USB cable from the back (that enables touch screen abilities) it went away COMPLETELY. so now i have to figure out how i'm going to power the monitor instead of powering it from the cig lighter (i needed to do this initially but i have procrastinated to do so because it's going to entail sacrificing a cable that came with the monitor.

thanks for all the tips you guys, eventually i'll post some pictures and stuff, tomorrow i'm getting the power re-run for the CPU, i'll be able to deal with that till i get the monitor permanately (spelling?) powered elsewhere...

pancit175 · 08-05-2007, 07:53 PM

Quote: Originally Posted by pancit175

I believe that the cig lighter wires is more prone to noise. And it is possible for the noise from the screen can be picked up through the motherboard to your audio output.

See, I told you!

User Name		Remember Me?
Password