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  • Higher wattage DC-DC converters?

    Since the 12V in most of the DC-DC converters (bar the big and expensive Opus) is unregulated, presumably that means a cheaper (lower wattage) one could be used if one hooked the 12V P4-ATX cable up directly the 12V from the car. There'd still be no regulation but now you've got a much higher power available to a more power hungry PC.

    The only downside is that the DC-DC psu's do have over-voltage protection that probably protects against voltage spikes. But if you're going to have to add decent regulation (via a tank circuit or the like), the PC is already protected against that.
    Progress: 80% - Permanent install left.
    Motion LS800 Tablet PC and dock.
    Vista, Bu-535 GPS, RoadRunner, MPT2006.

  • #2
    That is not correct. Realize that your main amount of current needs to be in the 5v and 3.3v lines, as well as the 12v. A 300 watt power supply is the wattages of all rails added up. For example (this is a typical 300watt PS):
    Voltage____Current___Power (Peak)___Power (RMS)
    +12v______15A______180watts______127.3watts
    +5v_______30A______150watts______106.1watts
    +3.3v_____28A_______92.4watts_____65.3watts
    Totals_______________422.4watts____298.7watts
    We will ignore the negative lines...

    So you see that running the +12v straight in will not work as intended.

    ColdPhreze
    14" LCD, EPIA MII-10000, 256MB, Wireless LAN, GPS, CDRW/DVD, ELM Scan,
    200wRMS inverter (for the screen), CarPC Pro v2.4 Power Controller,
    2 12" Pioneer Premiers, Sony 6x9s, Sony Xplode Class D mono block, Pheonix Gold A/B amp for highs

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    • #3
      Good point.

      Voltage____Current___Power (Peak)___Power (RMS)
      +12v______15A______180watts______127.3watts
      +5v_______30A______150watts______106.1watts
      +3.3v_____28A_______92.4watts_____65.3watts
      Totals_______________422.4watts____298.7watts


      I read an article that said most power supplies cannot provide their rated sustained max power output on all rails simultaneously. Whereas all the DC-DC converters I've seen claim to be able to do so.

      But since the mini box 200W psu's are mostly identical to their lower wattage versions, but with more power available on the +12V line, there probably isn't much point, pursuing this line of thought.
      Progress: 80% - Permanent install left.
      Motion LS800 Tablet PC and dock.
      Vista, Bu-535 GPS, RoadRunner, MPT2006.

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      • #4
        Originally posted by Arathranar
        Since the 12V in most of the DC-DC converters (bar the big and expensive Opus) is unregulated, presumably that means a cheaper (lower wattage) one could be used if one hooked the 12V P4-ATX cable up directly the 12V from the car. There'd still be no regulation but now you've got a much higher power available to a more power hungry PC.

        The only downside is that the DC-DC psu's do have over-voltage protection that probably protects against voltage spikes. But if you're going to have to add decent regulation (via a tank circuit or the like), the PC is already protected against that.
        ha ha ha.. if you want to fry your CPU that is...
        ***
        CarPC Ver 4 completed. Aopen i45GMT-HD, C2D mobile 2GHz. Photofast 64GB SSD. Novatel EU-850D

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        • #5
          I did say 'with suitable regulation'...
          Progress: 80% - Permanent install left.
          Motion LS800 Tablet PC and dock.
          Vista, Bu-535 GPS, RoadRunner, MPT2006.

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          • #6
            Originally posted by Arathranar
            I did say 'with suitable regulation'...
            that's where the money is, u see. proper regulation comes at a price. u can looking the sproggy designs to see how the design allows for clean voltage regulation.
            running a seperate device to the 12V line and use cheaper smaller power supply will just ended costing u.

            not to mention now u lack the integration required for your power up and down. There is a reason why OPUS is expensive, coz short of making your own, there isn't a good alternative solution.

            u might just want to consider making a sproggy urself....

            moo
            ***
            CarPC Ver 4 completed. Aopen i45GMT-HD, C2D mobile 2GHz. Photofast 64GB SSD. Novatel EU-850D

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            • #7
              But OPUS isn't a good solution for high speed pcs. Therefore, the only solution for now is an inverter/power supply/power controller. That's how I do it, and it works like a dream. And don't bust my balls about DC-DC being more efficient. When you are drawing that much current, you might as well turn on the car, and then it isn't a problem, noone should care if you waste a few watts.

              Here's a question: Has anyone tested the efficiency of the OPUS and other DC-DC power supplies and compared it to a good inverter with power supply? Do we really know if they are worth all that extra money? (Because you can have a inverter/power supply/power contoller for about $120 and will have 300 watts or more to power your pc.)

              ColdPhreze
              14" LCD, EPIA MII-10000, 256MB, Wireless LAN, GPS, CDRW/DVD, ELM Scan,
              200wRMS inverter (for the screen), CarPC Pro v2.4 Power Controller,
              2 12" Pioneer Premiers, Sony 6x9s, Sony Xplode Class D mono block, Pheonix Gold A/B amp for highs

              Comment


              • #8
                yup
                OPUS isn't meant to handle high wattage PC
                it's a matter of design considerations
                for u, power seems to be your drive... hence your solution (alternative will be forward invertors... which is even harder than building the sproggy)

                for others, heat, size, efficiency, ability to run with engine off, ability to run off battery continuously might be the primary drive. for eg. i ran a EPIA TC10000 (before it fried) normally, which is not suitable for continuous surveillance/ telematics. I am in the process of working with some developer to look into low power embedded device to handle that....

                it's all matter of different requirement. on that note, i reallty admire those guys who can design the power supply according to their needs and build them themself.... wish i have the ability to do so

                moo

                i
                ***
                CarPC Ver 4 completed. Aopen i45GMT-HD, C2D mobile 2GHz. Photofast 64GB SSD. Novatel EU-850D

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                • #9
                  I'm looking to minimize size. Sproggy and Opus are too big. Plus, where's the fun in building or buying someone else's work?

                  I can make a practically free guaranteed serial port driven shutdown controller so I don't need to buy that. Plus it will work exactly the complicated way I want it to .

                  Regulating just the 12V into the m/b is probably doable with a handful of cheap components with a tank circuit. Still working on that though...
                  Progress: 80% - Permanent install left.
                  Motion LS800 Tablet PC and dock.
                  Vista, Bu-535 GPS, RoadRunner, MPT2006.

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                  • #10
                    If you think you can do it cheaper than someone who is doing mass production or even low volume production, you have something to learn. I don't mean to discourage, but if you are trying to save some money, I assure you, you will spend more trying to get it to work than simply buying a workable solution. If you are simply wanting to learn/diy, go for it. I'll even help you out when I've got some time.

                    ColdPhreze
                    14" LCD, EPIA MII-10000, 256MB, Wireless LAN, GPS, CDRW/DVD, ELM Scan,
                    200wRMS inverter (for the screen), CarPC Pro v2.4 Power Controller,
                    2 12" Pioneer Premiers, Sony 6x9s, Sony Xplode Class D mono block, Pheonix Gold A/B amp for highs

                    Comment


                    • #11
                      yes. i am sure your tank circuit is smaller than the opus.

                      anyway. have fun.
                      ***
                      CarPC Ver 4 completed. Aopen i45GMT-HD, C2D mobile 2GHz. Photofast 64GB SSD. Novatel EU-850D

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                      • #12
                        Actually it will be...

                        But in general, I have many places I can stuff the battery and few I can put the Opus.
                        Progress: 80% - Permanent install left.
                        Motion LS800 Tablet PC and dock.
                        Vista, Bu-535 GPS, RoadRunner, MPT2006.

                        Comment


                        • #13
                          Got a question Dont know what inverter to get. I have usb 2..0 hub in my car and external dvd drive. THey both have ac-dc adapter. i am wondering how many watts inverter will work.

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                          • #14
                            Originally posted by ColdPhreze
                            If you think you can do it cheaper than someone who is doing mass production or even low volume production, you have something to learn. I don't mean to discourage, but if you are trying to save some money, I assure you, you will spend more trying to get it to work than simply buying a workable solution. If you are simply wanting to learn/diy, go for it. I'll even help you out when I've got some time.
                            There are also advantages to one off diy solutions that can make it cheaper too though. Being able to scavenge from dead electronics, not having to build a generic solution, getting samples, using tank batteries, etc.

                            I am thinking of buying the reasonably cheap and very small mass produced 200W mini box PSU to do the complicated portion. Digging up my atrophied electronics knowledge is a slow and painful process so I always welcome people correcting my misconceptions .
                            Progress: 80% - Permanent install left.
                            Motion LS800 Tablet PC and dock.
                            Vista, Bu-535 GPS, RoadRunner, MPT2006.

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                            • #15
                              Found these chips:
                              http://www.national.com/pf/LM/LM350.html#Datasheet
                              3-35Vin. 1.2-33Vout. Upto 3A (limited by 30W max power). ~$1.50 from mouser.
                              Definitely looks promising as the base of my voltage regulation circuit using the tank to survive the crank, a 200W snap-on to do most of the m/b voltage regulation, and these chips to post-regulate the 12V into the m/b.
                              Progress: 80% - Permanent install left.
                              Motion LS800 Tablet PC and dock.
                              Vista, Bu-535 GPS, RoadRunner, MPT2006.

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