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My plan: am I on the right track here?

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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
    2003 Mitsubishi Lancer CarPC Build Thread

  • #2
    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.)

    Comment


    • #3
      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
      2003 Mitsubishi Lancer CarPC Build Thread

      Comment


      • #4
        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
        My OLD 2001 Mitsubishi Eclipse GT:
        "The Project That Never Ended, until it did"


        next project? subaru brz
        carpc undecided

        Comment


        • #5
          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? )

          Comment


          • #6
            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
            2003 Mitsubishi Lancer CarPC Build Thread

            Comment


            • #7
              Thread moved to proposed setup.
              Originally posted by ghettocruzer
              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

              Comment


              • #8
                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....

                Comment


                • #9
                  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.
                  2003 Mitsubishi Lancer CarPC Build Thread

                  Comment


                  • #10
                    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?
                    2003 Mitsubishi Lancer CarPC Build Thread

                    Comment


                    • #11
                      don't go by max wattage-- there are many ways they can really fudge max wattage ratings.

                      have you heard those speakers at all? make sure that they sound goo dto you before you buy.

                      also, caps are useless. search for some of 'oldspark' posts, wher he goes into detail why even a small battery is better..
                      My OLD 2001 Mitsubishi Eclipse GT:
                      "The Project That Never Ended, until it did"


                      next project? subaru brz
                      carpc undecided

                      Comment


                      • #12
                        Originally posted by soundman98 View Post
                        don't go by max wattage-- there are many ways they can really fudge max wattage ratings.

                        have you heard those speakers at all? make sure that they sound goo dto you before you buy.

                        also, caps are useless. search for some of 'oldspark' posts, wher he goes into detail why even a small battery is better..
                        Nope, have not heard the speakers yet, I'll make sure i take a listen before. What type of speakers do you recommend if I have two 10's in the back? Can you direct me to a particular product? Budget for speakers is $300.

                        I'll research oldspark's posts. Thanks for the direction
                        2003 Mitsubishi Lancer CarPC Build Thread

                        Comment


                        • #13
                          Originally posted by doncarbone View Post
                          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?

                          Why do people think they get "extra power" from a cap? Or battery?

                          BUT - that is in reference to the alternator being too small which is how I interpret your (doncarbone) question... "... am I in good shape in terms of power here, or will my battery get molested by the above ....".

                          NOTE - I was looking for miserable & crying emoticons that reflect my feeling about dishonest people (re caps & batteries)... I 'm not flaming doncarbone nor anyone else that is conned or unsure - such technicalities ARE confusing!
                          And FYI - soundman98's reply cheered me up. Again!


                          NOTHING makes up for an undersized alternator except the removal of loads.
                          A bigger battery merely means longer reserve time until it flattens (ie, to make it home to a charger etc). (And a cap is essentially a very small battery.)

                          If you mean power surges that cause voltage dips - that's another issue - and that can get complex.
                          EG - alternators can typically supply (at least) twice their rated current for short durations/surges.
                          But the voltage drops can be in the distribution (voltage drop along cables, fuses, connectors).
                          But that shouldn't worry a good amp - ie, hi-power audio amps have SMPS (Switch-Mode Power Supplies = dc-dc converter) which should or could tolerate voltage dips.
                          For dip-sensitive loads, halving the distribution resistance (cables etc) HALVES the voltage dip. Otherwise caps are recommended, but usually small AGM batteries are better (& cheaper) than multi-Farad caps for that purpose. (The small 1.2AH or 7AH AGM battery is located near the amp instead of the cap - ie, at the same close location.) [There may be situations where a cap is superior, but whilst people argue things like ESR, they have no hope of figuring out if or when a cap is superior. (LOL!)]


                          Back to the alternator....

                          As soundman alluded - the only Wattage that is useful is RMS as that provides a "true power" figure. (Peak used to be 2x RMS, but I have seen peak commonly 3x and as high as 10-times which is just ******* pointless.)
                          But that's likely to be a maximum power consumption - eg, full volume, high voltage, etc.

                          Yes - use fuse ratings or RMS (input!) power as an estimate of you max alternator power requirement and cable sizes etc....
                          But what is your average real requirement?


                          Anyhow, irrespective of sizing, how do you know if your alternator is failing to keep up?
                          A voltmeter! IMO a voltmeter is the only way to confirm alternator sizing.
                          It also allows monitoring of charge state and battery condition.
                          But that I will leave for you to search. I'll only repeat so much ramble....

                          Comment


                          • #14
                            Originally posted by doncarbone View Post
                            Nope, have not heard the speakers yet, I'll make sure i take a listen before. What type of speakers do you recommend if I have two 10's in the back? Can you direct me to a particular product? Budget for speakers is $300.
                            as a rule, i do not make speaker recommendations-- every speaker sounds differently then others(to some a $10 boom box sounds great, to others, a $1 million stereo system is great), so any recommendation i make would be based on my opinion, and just 'cause its my opinion doesn't make it right..

                            my current stereo has cost about $1,500, so the specific products that make me happy are a little pricer then what you originally indicated you wanted to spend.

                            the best suggestion is to take a demo disc of your favorite music to the car audio store, and listen to the different speakers, and see what fits your style.

                            and if the shop doesn't let you demo the speakers you are looking at, leave. i have had shops go as far as to allowing me to setup the subs in my own car to hear how they sound, and there is no reason to not hear what you are getting. it is like buying a car without test driving..


                            depending on how interested in speaker setups you are, you could also build your own setup using separate speakers from companies like madisound.com, or parts-express.com.

                            this gets a little tougher because there is really no way to listen to the speakers before buying..

                            i changed my front speakers for under $150(using some Dayton ND28F-6 tweeters, and some peerless brand 6 1/2" hds mids) to something that rivals the sound of $400-600 car-audio specific speakers..

                            the trick with this is to first learn what you desire in a speaker(loud highs, or boomy bass, etc.) and then locate the very detailed reviews that list the speakers characteristics.

                            a good starter site is http://zaphaudio.com/ they have tested a lot of speakers, and give very detailed results..
                            My OLD 2001 Mitsubishi Eclipse GT:
                            "The Project That Never Ended, until it did"


                            next project? subaru brz
                            carpc undecided

                            Comment


                            • #15
                              Originally posted by soundman98 View Post
                              the best suggestion is to take a demo disc of your favorite music to the car audio store, and listen to the different speakers, and see what fits your style
                              i actually have a fairly eclectic taste in music -- so really im looking for something 'mutli-purpose' or fairly well rounded. my biggest concern above all else is that the dual 10" subs i'll have blasting in the trunk might drown out the speakers...which i've found from listening to a few of my buddy's systems is awesome for showing off the bass, but not very practical for enjoying the music.

                              having never had a sound system of my own before, what can i expect out of the 2 10's i listed above (MTX)? does anyone have these?

                              thanks for the response man
                              2003 Mitsubishi Lancer CarPC Build Thread

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