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Thread: My plan: am I on the right track here?

  1. #1
    Constant Bitrate doncarbone's Avatar
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    My plan: am I on the right track here?



    What i hope to accomplish:

    a) Have my deck to control bass/speaker volume, AUX etc
    b) Have the netbook take care of all general windows **** like videos, music, internet (has a SIM card built in with mini mags for improved signal)
    c) Get all this securely mounted/fastened
    d) Make sure my battery does not croak

    A few extras about the items in the diagram (numbered)

    1. I have constructed an aluminum frame that is mounted on the dash to host the netbook (above the deck). Netbook LCD is flipped over and laptop acts like tablet PC
    6. The inverter i am hoping to put under the driver's seat...but am i at any risk of sound problems if i also choose to run my amp power cable on the same side...or is it only the RCA/speaker cables that should be on the opposite side?

    This is my first attempt at anything even remotely related to car audio/fabrication/carputers. I've dealt with computer hardware/coding before (gaming PC's, web development...) but other than putting gas in my car, i've never done much with it. So just to make absolutely sure i don't go and mess something up big time, if I can have a few of you guys skim over this and offer me any advice or give me the thumbs up if it's all good, i'll be on my way and post pics when im done!

    One problem I have run into so far with this is that when i plug my laptop (headphone jack) into the AUX input on my deck and play music, i get this fuzzy noise synchronous to my engine. i took out the AUX cable and popped in a pair of earbuds into my netbook and the static crap was gone. am i correct in assuming my radio/deck is therefore not grounded properly?

    thanks again guys,

    -- Dc

  2. #2
    Raw Wave
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    Use a dc-dc for the netbook, not an inverter (unless you have specific reasons for the inverter). And I assume you mean a relay controlled by a steering wheel or other switch.


    Engine noise is probably a ground loop, else grounding, but could be wires parallel with noisy wires, or sharing a common path. (Or faulty noise suppression on alternators etc.)

  3. #3
    Constant Bitrate doncarbone's Avatar
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    Quote Originally Posted by OldSpark View Post
    Use a dc-dc for the netbook, not an inverter (unless you have specific reasons for the inverter). And I assume you mean a relay controlled by a steering wheel or other switch.


    Engine noise is probably a ground loop, else grounding, but could be wires parallel with noisy wires, or sharing a common path. (Or faulty noise suppression on alternators etc.)
    It might be the parallel wires -- at the moment my netbook power cable runs through the center console where many other wires run.

    Why do you recommend DC-DC and not the inverter? I am using the inverter because i may also want to plug some other items into it later (mainly for passengers who occupy the back seats as the inverter is facing them, under the driver's seat)

    Edit - sorry, yes it is a relay switch, 30A

  4. #4
    MySQL Error soundman98's Avatar
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    the reason for the dc-dc is less conversion, and dc-dc's also have higher switching rates.

    ac inverters create a/c power from 12v dc-- during this process, they use switching regulators, that work at 60hz-- the human hearing range is 20hz-20,000hz--so this can really mess with your audio signal

    dc-dc power supplies still use switching regulators to increase, or decrease the output voltage, but they switch at a much higher rate, so there is much less chance of audio interferance.

    there is also less conversion-- because the dc-dc is still keeping everything in the dc realm...


    you definitely have a ground loop-- this could be caused by the radio, and netbook being grounded in different spots, or a poor ground somewhere in the system

  5. #5
    Raw Wave
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    It's mainly the efficiency. Ignore the noise issue (see below).


    But you gave a valid reason for the inverter. Like me, you have OTHER loads you want to run.
    Hence I used a much cheaper inverter (plus one spare) as a universal solution.
    Inverters are cheaper, easier to replace any failed parts, and safe.

    It was only as I stumbled into cheap dc-dc converters for each item that I used them, though I still carried an inverter for backup (since their AC PSUs were along for the ride for motels etc). That was mainly for things like mobile phones & videocams.
    As for my girlfriends netbook, I got a ~50W dc-dc for under $25.


    More on converter noise....
    Don't worry about their noise - both dc-dc and dc-ac used high frequency switching (typically 50k-100kHz) so both are as likely for that noise.
    But the inverter's output AC which is rich in harmonics if it's the common non-sinewave output (eg, 60Hz, 180Hz, 300Hz).

    Both types can have the switching interference on their outputs.
    (I doubt that any modern inverters would use 50/60Hz internal conversion - they'd be too big & heavy! Ever seen how big a 1kW mains transformer is? )

  6. #6
    Constant Bitrate doncarbone's Avatar
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    Thanks for the replies. I think i will stick with the inverter, later on I can do DC-DC...i've already bought it and just spent the last few minutes lengthening/soldering wiring that will go from the inverter to the battery.

    the sound issue was fixed too -- all i did was moved the power wires for the netbook from the center console (where it was running alongside other wires) to the passenger side. now it works just fine no sound problems whatsoever!

    As for the relay switch -- I checked, the one i have is actually NOT a relay switch, its a rocker switch (12VDC) rated at 16 amps -- good enough?? The reason i want the switch is obviously to turn the inverter off when the car ignition is turned off. There is already a switch on the inverter but because it'll be hidden under a seat i wanted to add in a simple switch i can click near the steering wheel. Will this switch i have not be sufficient? Is a relay switch an absolute must here?

    Thanks

  7. #7
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    Bugbyte's Avatar
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    Thread moved to proposed setup.
    Quote Originally Posted by ghettocruzer View Post
    I was gung ho on building a PC [until] just recently. However, between my new phone having internet and GPS and all...and this kit...Im starting to have trouble justfiying it haha.
    Want to:
    -Find out about the new iBug iPad install?
    -Find out about carPC's in just 5 minutes? View the Car PC 101 video

  8. #8
    Raw Wave
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    Inverter is fine.... Good reasoning etc.


    Re the switch, I was assuming it was ON the steering wheel, and hence should not be high current.

    You can try the 16A switch, but see how hot it gets...
    1: I don't like using switches for anything near 10A or above.
    2: My 16A rated switch melted for an 80W (7A) fan.
    3: Assume 30A for a 300W inverter at max output (ROT - divide dc-dc & dc-ac output Wattage by TEN for (max) input current on a 12V system (or divide by 5 if the unit works down to 6-8V etc).
    4: 16A input @ 12.6V = 200W implies max 150W output for a good & new 16A switch.
    5: A 30A or 40A relay is best....

  9. #9
    Constant Bitrate doncarbone's Avatar
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    Quote Originally Posted by OldSpark View Post
    Inverter is fine.... Good reasoning etc.


    Re the switch, I was assuming it was ON the steering wheel, and hence should not be high current.

    You can try the 16A switch, but see how hot it gets...
    1: I don't like using switches for anything near 10A or above.
    2: My 16A rated switch melted for an 80W (7A) fan.
    3: Assume 30A for a 300W inverter at max output (ROT - divide dc-dc & dc-ac output Wattage by TEN for (max) input current on a 12V system (or divide by 5 if the unit works down to 6-8V etc).
    4: 16A input @ 12.6V = 200W implies max 150W output for a good & new 16A switch.
    5: A 30A or 40A relay is best....
    Ok, i think you are right and others i have asked have also suggested the 40A relay.

    fortunately the store i bought the switch from is pretty damn good with returns so i can take my switch back and get a relay...i'll also pick up an inline fuse which i can put right next to the + terminal on the battery.

  10. #10
    Constant Bitrate doncarbone's Avatar
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    Update:

    So everything works -- monitor has been installed and is powered. sound quality is decent on stock speakers but im eager to update my sound system!

    here's what i have lined up:

    Speakers:

    - 4 x Alpine SPS-600 (recommended power range 80w per pair)

    Subwoofers:

    - 2 x MTX 12" JackHammers w/ vented box - max 1200w

    Amps:

    - MTX 4 channel amp (for speakers) - total max power 800w
    - MTX 1 channel amp (for subs) - total max power 1200w

    My question here is - am I in good shape in terms of power here, or will my battery get molested by the above + the 300w inverter & laptop? also is my setup pretty good or should i look at alternative products?

    what can i look at to keep myself safe? can anyone recommend a solid capacitor or possibly an extra battery to ensure i have enough power?

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