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  • Power Requirement and Audio

    I'm getting a 1996 Jeep Cherokee on March 9th and have been researching how to build setup for about 2 months now (as in a computer running everything). I got my hands on the O'Reilly "CAR PC HACKS" book and used that as a foundation for everything I plan to do.

    The easiest way to ask my questions is to build a list with what I want to install and ask the appropriate question next to the item, so here goes:

    1. I am going to upgrade the alternator. Questions: Wow, there are like ... 4 alternators for a 1996 Jeep Cherokee, can I use an alternator that wasn't built for the car/SUV? How many amps should it output? I want one with a dual output for two batteries, is this suggested? I really want dual output and overkill is never bad, but I would like to spend under $300: does such a thing exist that fits those requirements?

    2. Power requirements, the flippin 'ell! I can't for the life of me even conceive what kind of power requirements two amps (one for sub, one for speaker. I'm a high fidelity guy), a 1000 watt inverter, a 1.2 farad capacitor, a second deep cycle battery, a touchscreen LCD, a relatively low end PC, a GPS receiver, and any other peripherals hooked up to my PC (keyboard w/ mouse, soundcard, radio adapter, etc...) will need. Apparently this is supposed to be a cake equation but I've spent about three hours to no avail trying to calculate power requirements but it never comes out right. What is a good round figure that I should be ok with, in Amps.

    3. What would the price run to get a dash fabricated? Is it recommended that I "tweak" my dash myself to install my LCD? I have never undertaken a real mod project and lack the fine motor skills that I perceive are needed...

    4. Audio. It seems the easiest way to hook up audio would be to have one single channel amp for the sub and one two-channel amp for the speakers (I can match the power w/ amps to speakers). But, how does the computer output to the speakers? One headphone out hardly seems capable of outputing high fidelity sound considering it would very... unbalanced? And what would I have to do in order to get sound to the sub? When I try and piece together how to get sound from the computer to the amp to four speakers and a sub it just seems like something is missing...

    5. Computer/sound card. Um, how does a integrated sound card cut it? That seems to be the card of choice. i.e. no card. If the head unit is removed there has to be a line level sound card capable of evenly distributing sound to two channels (front left+rear left, and front right+rear right) computer sound cards just aren't designed to do this, its always front left+center+front right, and then rear left+rear right, plus a separate channel for a sub. Computer sound, if I am correct, if normally connected in a car would cause the frost speakers to output the sound normally heard on the left speakers and the rear sound to produce the sound heard on right speakers. Frankly, I'd rather my head not explode as I am driving down the road. How have others hooked their car sound up to their computer? And achieved true high fidelity, balanced sound?

    6. Is there an easy way to hook all deviced that must turn on with the car up? A relay switch for the inverter, a power sequencer for the PC, another relay for the capacitor (not to mention a slew of fuses); this all seems a bit too.. demanding? Is there an easier way, for example, a power sequencer with about five outputs/inputs?

    7. Cable. Every cable apparently must be shielded, but every cable is not made shielded, so how do I get every cable shielded? Accessory lines, VGA cables, computer power cables, lines to and from the battery...

    8. This is definatley harder than it looks :/ Any answers are welcome, and corrections of my understanding are welcome, there just seems to be alot that I don't undertand here. Alot of people seem to be able to make entire systems run perfectly without having a large inverter, a crappy alternator, no capacitor, a tiny tiny amp... I was made to understand that a sound system+computer+GPS = hella power hog = upgrade everything.

    <EDIT> Ah, fyi, I get at least 50% off anything that has to do with cars at best buy; so if you know of any solution that will help me with any problem it would be perfect if I could find it at best buy.
    <EDIT>Ok, I looked at MAXX and Iraggi alternators and I can get "high performance" for a moderate price. The question is as follows: the idle output on a high performance alternator seems to be less than crappy, how would a 100 amp output from a 200 amp alternator (or 75 from a 180) affect the operation of my equipment? I live just outside of D.C. so I am rarely sustaining any high speed for a long period of time, it's purely stop and go here, so if my alternator can only supply half my power needs on idle than how will that affect my battery? I'm going to be using a 2 Farad Capacitor as well as a second battery (I need a suggestions for a passenger safe battery 55+AH) so will it really be that big an issue? And would I have to leave my car in the driveway for an hour with a brick on the gas peddle in order to get everything initially charged, as I figure it would take a very long time, if ever, to compleley charge with the kind of traffic I have to deal with?

  • #2
    I will simply say that you need a 120A alternator at minimum...anyway...but bigger is better of course...the amp rating is based on a certain rpm, so at idle usually they are not producing the max power.

    The more battery you have, the longer you can run the system with the battery off...having a spare isolated battery to start the engine in a remote location is always a good idea.
    current projects

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    • #3
      So a dual output alternator isn't really going to be recommended, I was looking at running just an isolated battery as one of my options, but I remember reading something about having a second battery hooked up as an isolated battery requires ALOT of extra power to charge. If a 120amp alternator will be good then would a blue top be a good second battery?

      Lol, and nice number of posts btw ^^ Do I get to make a wish?

      Comment


      • #4
        ok..i haven't been here in awhile so i'll jump right in here.

        1. i've had a 90 amp alternator in my car for over 20 years and never had a problem running 600 watts. just get the largest output that will fit in your vehicle. i run a dual battery setup using a dual battery isolator. get a deep cycle for the rear. only drawback to this system is that if one of the battery calls for a charge they both will charge. still--never had a problem here.

        2. seeing how you are asking all these questions i assume you want to do this right so just get a dc/dc ps.

        3. just practice on something

        4. get a good sound card and either use the pc volume control or you can get an inline volume control. david navone.com--i recommend him to everyone. search for a sound card everyone here uses. i have an audigy and it sounds fine-but the output voltage is lower than a regular car head unit. there are audio processors that have built-in line drivers--try audio control.

        5. see above lol

        6. a dc/dc ps will have an ignition trigger wire that will send a signal to the motherboard to start up. of course there is a jumper between the two. i use the yellow wire on the ps to a relay to trigger all my screens, amps and such.

        7. most decent quality cables are shielded. twisted pair are best.

        8. good luck! and don't be afraid to search. all the answers are right here. when i joined this forum people were just getting into screens and were using 4 line lcd's to read their song titles!
        99.9% complete.

        http://www.cardomain.com/ride/212327

        Comment


        • #5
          if you got all that info from that book i'd say it's either outdated, poorly written, or generalized.

          1) i'll let you do the legwork on this one. i ran the stock alt. with my xtant 603x amp (100 amp fuse on that bad boy) and pc. w/o any problems.

          2) drop the inverter, get a mini-itx board, drop the cap, get the proper gauge wiring and upgrade 'the big 3'
          3)ask someone on here to do it for you or go to a car audio shop

          4-5) there are a bunch of multi chan cards. do some research on this. you can get a 4 chan amp, use two chans for the front speakers, bridge the rear chans for the sub and be done with it. Most amps will accept a stereo input for all four chans (there will be a switch that sends the information to all the channels) all you have to do from there is futz with the amps internal x-overs. This will give way to letting you use a nicer cleaner sounding dac. check out the usb dac thread in the audio subforum for a nice dac and a great hack.

          6) battery-> primary fuse -> fused distrobution block->dc/dc psu and amps

          7)vga's are usually shielded, you don't need sheilding on power wires (to and from battery) usb is usually shielded, rca's are usually shielded

          why do you need two batteries? do you plan to use this as shows? a single deep cell battery will be fine for most instances. I have an optima and it's fine. you are overcompllicating this. go over and read the faqs on this forum and realize how much better off you will be. My best advice is mimic someone that has a system that is up and running and stable. don't try to be a pioneer your first time out. My core system is basically a default car computer system and it's worked flawlessly. I have made some upgrades and improvements (mainly in the audio area) but the core is unchanged.
          New System in progress:
          M10k
          Phaze TD1500 ~> Dynaudio MD130
          Phaze TD1500 ~> Seas g18rnx/p
          Zapco Ref 500.1 ~ 12" tc-9
          Behringer DCX2496 ~ Envision Electronics psu
          Transflective Xenarc

          My Car Pc Install
          My Boat Pc worklog

          Comment


          • #6
            kk, lovin the input so far guys, ty much! Um, when referring to ps, are we abbreviating "power supply" or "power sequencer?"

            Originally posted by albysure View Post
            6. a dc/dc ps will have an ignition trigger wire that will send a signal to the motherboard to start up.
            But does it provide and on/off delay?

            Also, I'm going to be eating a little more than 600 watts, remember it isn't just a PC, it's also a rather over-complicated sound system.

            Originally posted by scott_fx View Post
            i'll let you do the legwork on this one. i ran the stock alt. with my xtant 603x amp (100 amp fuse on that bad boy) and pc. w/o any problems.
            You are also driving a corvette the stock alt is assumabley a little bit beefier of a stock alt than that you might expect in a "lesser" vehicle. Also, a good sound system alone usually draws about 100amps. I found a decent power equation: 40% stock alt+50% battery bank (ah)+average audio (100amps)+my junx (probably 25amps) that ends up around 230amps, and thats assuming your getting the alternators maximum output.

            why do you need two batteries? do you plan to use this as shows?
            I plan to use two batteries so that my car will start in the morning for example, if I am exceeding the alternators output even by a little, I will eventually completely drain my main battery. Or, if I leave the PC or inverter on overnight (which I would like to install for the sake of the convenience of standard house current in my car); now this shouldn't happen if I am able to wire any relays or sequencers correctly. Also a second battery would prevent the voltage drop that occurs at engine start.

            Also, could either of you answer my last edit to the first post?

            Comment


            • #7
              Originally posted by Otterski View Post
              kk, lovin the input so far guys, ty much! Um, when referring to ps, are we abbreviating "power supply" or "power sequencer?"

              But does it provide and on/off delay?
              Most good dc/dc power supplies (m2-atx, opus, dsatx) provide startup/shutdown capabilities. There is usually no need for a separate psu and a startup/shutdown controller.

              Sounds like the others in this thread have answered the other questions pretty good. If you can do compact flash, it will help. There have been one or two times this winter where my laptop hard drive hasn't spun up for about 5 minutes because it's so cold. In my next carpc incarnation (lol, I crack myself up), I'll get a mobo with cf or some other bootable solid state media so I don't have to deal with that issue.
              My Worklog

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              • #8
                Originally posted by Otterski View Post
                1. I am going to upgrade the alternator. Questions: Wow, there are like ... 4 alternators for a 1996 Jeep Cherokee, can I use an alternator that wasn't built for the car/SUV? How many amps should it output? I want one with a dual output for two batteries, is this suggested? I really want dual output and overkill is never bad, but I would like to spend under $300: does such a thing exist that fits those requirements?
                You need to use an alternator designed for your engine. Else there will be a lot of fabrication to get it to mount correctly. No matter what the max output is, you need to consider what the idle output is. Compare those numbers, not necessarially max. A HO alternator for under 300 is a bit tough.

                I just purchased one for my GTi that retails for 650...120 amps at idle, 250 max. However, because I'm competing and sponsored by some companies, I didn't pay that.

                2. Power requirements, the flippin 'ell! I can't for the life of me even conceive what kind of power requirements two amps (one for sub, one for speaker. I'm a high fidelity guy), a 1000 watt inverter, a 1.2 farad capacitor, a second deep cycle battery, a touchscreen LCD, a relatively low end PC, a GPS receiver, and any other peripherals hooked up to my PC (keyboard w/ mouse, soundcard, radio adapter, etc...) will need. Apparently this is supposed to be a cake equation but I've spent about three hours to no avail trying to calculate power requirements but it never comes out right. What is a good round figure that I should be ok with, in Amps.
                For the amplifiers, check this wiki article, it will help to explain some of the equations: http://www.mp3car.com/wiki/index.php/Amplifier

                No need for a 1.2 farad cap, it won't really do any good. If you want to use a cap, get a bigger one.

                A 1k watt inverter? Why? Inverters cause a lot of problems and a lot of noise. Go with a DC-DC PSU, if you need more power, string them together.

                As for power, see this wiki page: http://www.mp3car.com/wiki/index.php/Power

                3. What would the price run to get a dash fabricated? Is it recommended that I "tweak" my dash myself to install my LCD? I have never undertaken a real mod project and lack the fine motor skills that I perceive are needed...
                Once you get everything installed, you can always take the car and screen to a shop and have them fabricate it. However, fabrication is not cheap. It takes a good deal of time and you're paying for someone elses time and knowledge. You can give it a go for yourself, just spend some time in the fabrication forum.

                4. Audio. It seems the easiest way to hook up audio would be to have one single channel amp for the sub and one two-channel amp for the speakers (I can match the power w/ amps to speakers). But, how does the computer output to the speakers? One headphone out hardly seems capable of outputing high fidelity sound considering it would very... unbalanced? And what would I have to do in order to get sound to the sub? When I try and piece together how to get sound from the computer to the amp to four speakers and a sub it just seems like something is missing...
                Spend some time in the car audio forum. This is a topic that's covered quite often....especially since just about every newbie that comes into this hobby asks the EXACT same question. There are a few options, only you can decide which one meets your needs.

                5. Computer/sound card. Um, how does a integrated sound card cut it? That seems to be the card of choice. i.e. no card. If the head unit is removed there has to be a line level sound card capable of evenly distributing sound to two channels (front left+rear left, and front right+rear right) computer sound cards just aren't designed to do this, its always front left+center+front right, and then rear left+rear right, plus a separate channel for a sub. Computer sound, if I am correct, if normally connected in a car would cause the frost speakers to output the sound normally heard on the left speakers and the rear sound to produce the sound heard on right speakers. Frankly, I'd rather my head not explode as I am driving down the road. How have others hooked their car sound up to their computer? And achieved true high fidelity, balanced sound?
                I'm not sure where you get that the card of choice is onboard? Remember that most folks on this board are computer people. Audio doesn't really mean too much, just as long as it works and you can tell what you're listening to.

                Again, hit up the car audio forum, there's a lot of information on this.

                6. Is there an easy way to hook all deviced that must turn on with the car up? A relay switch for the inverter, a power sequencer for the PC, another relay for the capacitor (not to mention a slew of fuses); this all seems a bit too.. demanding? Is there an easier way, for example, a power sequencer with about five outputs/inputs?
                again, a DC-DC power supply...not an inverter.

                7. Cable. Every cable apparently must be shielded, but every cable is not made shielded, so how do I get every cable shielded? Accessory lines, VGA cables, computer power cables, lines to and from the battery...
                Where do you get that EVERY cable must be shielded?

                RCAs need to be shielded...and for the rest, just use proper install techniques. Never run RCAs next to power, etc.

                8. This is definatley harder than it looks :/ Any answers are welcome, and corrections of my understanding are welcome, there just seems to be alot that I don't undertand here. Alot of people seem to be able to make entire systems run perfectly without having a large inverter, a crappy alternator, no capacitor, a tiny tiny amp... I was made to understand that a sound system+computer+GPS = hella power hog = upgrade everything.
                That's just not the case. If you're running small amps, this really isn't the case.

                <EDIT>Ok, I looked at MAXX and Iraggi alternators and I can get "high performance" for a moderate price. The question is as follows: the idle output on a high performance alternator seems to be less than crappy, how would a 100 amp output from a 200 amp alternator (or 75 from a 180) affect the operation of my equipment? I live just outside of D.C. so I am rarely sustaining any high speed for a long period of time, it's purely stop and go here, so if my alternator can only supply half my power needs on idle than how will that affect my battery? I'm going to be using a 2 Farad Capacitor as well as a second battery (I need a suggestions for a passenger safe battery 55+AH) so will it really be that big an issue? And would I have to leave my car in the driveway for an hour with a brick on the gas peddle in order to get everything initially charged, as I figure it would take a very long time, if ever, to compleley charge with the kind of traffic I have to deal with?
                100 amp is fine. Consider that if you have a 100 amp stock alternator, you're putting out VERY little at idle...just look at the number for a HO alternator.

                I'd also recomend: www.highoutputalternator.com

                Jan Bennett
                FS: VW MKIV Bezel for 8" Lilliput - 95% Finished

                Please post on the forums! Chances are, someone else has or will have the same questions as you!

                Comment


                • #9
                  Originally posted by Otterski View Post
                  kk, lovin the input so far guys, ty much! Um, when referring to ps, are we abbreviating "power supply" or "power sequencer?"
                  Power Supply.


                  But does it provide and on/off delay?
                  Yes.

                  Also, I'm going to be eating a little more than 600 watts, remember it isn't just a PC, it's also a rather over-complicated sound system.
                  I promise, it's not over complicated. It's just a basic system. Your PSU is not going to power your amps, just the computer components.

                  I plan to use two batteries so that my car will start in the morning for example, if I am exceeding the alternators output even by a little, I will eventually completely drain my main battery. Or, if I leave the PC or inverter on overnight (which I would like to install for the sake of the convenience of standard house current in my car); now this shouldn't happen if I am able to wire any relays or sequencers correctly. Also a second battery would prevent the voltage drop that occurs at engine start.
                  EXACTLY what amps are you going to be using? I'm guessing that your 1000watt sub amp is in all reality not 1000watts RMS.
                  Jan Bennett
                  FS: VW MKIV Bezel for 8" Lilliput - 95% Finished

                  Please post on the forums! Chances are, someone else has or will have the same questions as you!

                  Comment


                  • #10
                    Originally posted by scott_fx View Post
                    1) i'll let you do the legwork on this one. i ran the stock alt. with my xtant 603x amp (100 amp fuse on that bad boy) and pc. w/o any problems.
                    I've been running my stock alternator on my GTi for close to 5 years now.

                    At most, I've been running about 3000 watts RMS (NOT max mind you). No problems so far.

                    People tend to blow the whole alternator thing out of the water really.
                    Jan Bennett
                    FS: VW MKIV Bezel for 8" Lilliput - 95% Finished

                    Please post on the forums! Chances are, someone else has or will have the same questions as you!

                    Comment


                    • #11
                      Sweet, thank you RedGTiVR6. I spent a notepad a good amount of time with a few friends puzzling over everything today and I think we've got a pretty good solution. As for the audio situation, I'm keeping a head unit. I found a great head unit with a 1/8" in on the rear that I can easily hook up a sound card to. I will then have the head unit output to a mono for the sub and a four channel (one for each speaker). The set up will be quite easy and consume minimal power. I am set on this option as a few quick sound comparisons told me that a head unit amp = crap, post-amplified sound from a crap computer sound card = still superb sound. As for the inverter and capacitor, I trashed that idea as everyones recommendation (other outside mp3car suggested the same). Apparently a second deep cycle battery will work for me and my needs, later I will upgrade the amp as it will take a few hundred hours of operation to drain the deep cycle for the first time, and even when I do... it's a deep cycle, recharge is no prob I can just power down my sound system and PC. Eventually I am going to get a 200 amp iraggi though (100 amp idle). The DC/DC power supply sounds great, I was anticipating having to create my own device to provide appropriatley timed power, didn't realise there was aftermarket products designed to do just that. I am looking at a via set up for the computer now and an 8" lilliput. Notebook harddrives are what I am going to go with. Compact flash for me is just not an option, my entire music collection is going on this computer (about 130 gigs) which would be a very large array of flash cards The only things I have left to puzzle over is the fabrication of the dash, which I guess I'll just practice on myself (assuming I can find some junked XJs), and the gauging of all the wires, which I can figure out, I'm just lazy atm. Alright guys thankyou so much for helping get this project going! Well, on paper at least. Looking forward to becoming part of the communiting and sharing any advice I learn along the way as well as absorbing all info anyone will feed me. Thanks again, wish me luck! I'm going to be doing a few schematics as well as make an order of virtually every part before I start on the project. I also have a little cosmetic work to be done to the car, and I need to clear out the spare tire from the back and put it on a rear mount to make room for any electronics that I dont want under the seat. Also givin her a new paint job from vomit green to black Ill start a project thread else where with before and after pictures if ya'll want.

                      Sorry, I'm not the biggest fan of paragraphs...

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                      • #12
                        Originally posted by Otterski View Post
                        Compact flash for me is just not an option, my entire music collection is going on this computer (about 130 gigs) which would be a very large array of flash cards
                        You can put all your programs on the flash drive and all your music on a hard drive...it's what I was going to do. I have close to 225 gigs of music now so I can feel your pain there.
                        Jan Bennett
                        FS: VW MKIV Bezel for 8" Lilliput - 95% Finished

                        Please post on the forums! Chances are, someone else has or will have the same questions as you!

                        Comment


                        • #13
                          Originally posted by RedGTiVR6 View Post
                          You can put all your programs on the flash drive and all your music on a hard drive...it's what I was going to do. I have close to 225 gigs of music now so I can feel your pain there.
                          Exactly my problem. I've got 2 terabytes of music and video. I've come to the conclusion that I'll probably use some sort of syncronizing program like the one v8 scimitar has. Isolating the operating system by itself is a good idea on its own. Having a second drive for applications (frontend, music player, gps software, etc.) and yet another drive (or more if possible) just for data (music, video, games, etc.) is a great design, but consumes a lot of power and space...
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