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  • Help with Making a 5V/3A voltage regulator

    Hello All :

    I am working on building a 5V/3A voltage regulator from my car battery. I am going to use this to power my Audigy2 NS. I am a little lost on the AMP aspect of the regulator. The 7805 is 5V/1A - how do I boost the AMPS?

    My soldering skills are there - I understand the basics - just don't understand what parts to buy and how to link them so that I can power my external USB soundcard. Any help is greatly appreciated!!! I did search and haven't found the exact topic I need help with.
    2003 Chevy Tahoe Z71
    STOLEN - M10000, 512MB, 60GB 2.5" HDD, 7" Custom mounted Lilliput, Morex 3688 Case, 90W PSU w/ ITPS, GPS & CD-RW/DVD. New parts ordered for the next generation!

  • #2
    One option:
    http://www.mp3car.com/vbulletin/showthread.php?t=32868
    Be sure to read the whole thing as their is a problem with that schematic.

    There in a 7805 in a T-03 package I believe that supply's 3 amps.
    Simple to build, but it gets pretty hot.

    You may want to look for a cigarette lighter adapter that will do it and chop off the plug to hard wire it in.

    -Mario

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    • #3
      Be prepared to dissipate ~25W of heat at 3A.

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      • #4
        TI PT6625 (5V/6A). It doesn't get any easier. I use a variant (PT6653D 5V/5A) to power my Audigy NX. It works great and doesn't get hot at all. Search for a post by Rob Whitney.
        2004 4runner

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        • #5
          What he said...

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          • #6
            m3rdpower - I have used the 7805 but they are only 1amp and I need 1.5amps minimum. I haven't seen a 3 amp version - but if it is out there I would love to work with it because the 7805 was VERY easy to work with. Also, I posted that schematic and built it last night. there were a few errors, but I have since modified them and I am re-working everything tonight after blowing the 10mf cap on the 5V out.

            MrPerfectionest - I have a really nice heat sink which worked well with 5A last night - it gets hot - but not crazy hot!

            Rando - I will check out the TI stuff - I have read a lot about it - but the only place I have seen to get them is online. I am always in to buying and building - I can never wait!!! LOL Anyways - I will research the PT6625 and perhaps build V2.0 with that one! Thanks guys!!!
            2003 Chevy Tahoe Z71
            STOLEN - M10000, 512MB, 60GB 2.5" HDD, 7" Custom mounted Lilliput, Morex 3688 Case, 90W PSU w/ ITPS, GPS & CD-RW/DVD. New parts ordered for the next generation!

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            • #7
              The TI and 7805 hook up to your circuit essentially the same. Input, GND, Output with caps across the input and output rails. The TI also has an enable/disable input, feedback, and some voltage adjustment pins that you can ignore. You're right, you can probably only order them on-line.

              The linear regulator approach probably isn't going to work for you unless you're willing to use a massive heatsink and fans. 25W+ of heat is a crap load! You've already waited a day just for these replies. If you're clever, you can have the TI chip at your place by tomorrow / Thursday at the latest.
              2004 4runner

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              • #8
                rando - where is the best place to buy them? and I appreciate your help!

                Why does the linear chip create more heat?
                2003 Chevy Tahoe Z71
                STOLEN - M10000, 512MB, 60GB 2.5" HDD, 7" Custom mounted Lilliput, Morex 3688 Case, 90W PSU w/ ITPS, GPS & CD-RW/DVD. New parts ordered for the next generation!

                Comment


                • #9
                  Originally posted by rando
                  The TI and 7805 hook up to your circuit essentially the same. Input, GND, Output with caps across the input and output rails. The TI also has an enable/disable input, feedback, and some voltage adjustment pins that you can ignore. You're right, you can probably only order them on-line.

                  The linear regulator approach probably isn't going to work for you unless you're willing to use a massive heatsink and fans. 25W+ of heat is a crap load! You've already waited a day just for these replies. If you're clever, you can have the TI chip at your place by tomorrow / Thursday at the latest.
                  I agree, they get hot as hell.
                  I still have my fixed and variable output I built in 1985 in high school.

                  I would assume the TI that rando mentioned is switching type regulator which is why it doesn't run hot like any 78xx series linear regulator.

                  -Mario

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                  • #10
                    What about this ?
                    http://www.national.com/ds/LM/LM123.pdf
                    2003 Chevy Tahoe Z71
                    STOLEN - M10000, 512MB, 60GB 2.5" HDD, 7" Custom mounted Lilliput, Morex 3688 Case, 90W PSU w/ ITPS, GPS & CD-RW/DVD. New parts ordered for the next generation!

                    Comment


                    • #11
                      Originally posted by nirvanades
                      That will get pretty hot to as it works pretty much the same as a 78xx series.

                      Honestly, rando's suggestion is the best way to go.
                      Again, you can always run to Walmart or something tonight to see if they have a cigarette lighter adapter that will do it as they use something more efficient than a 78xx series. Return it after you build rando's solution...

                      -Mario

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                      • #12
                        Kick *** - I really appreciate ALL of your help! I'll let you know how everything turns out
                        2003 Chevy Tahoe Z71
                        STOLEN - M10000, 512MB, 60GB 2.5" HDD, 7" Custom mounted Lilliput, Morex 3688 Case, 90W PSU w/ ITPS, GPS & CD-RW/DVD. New parts ordered for the next generation!

                        Comment


                        • #13
                          Which one do I get? ,,, D, M, R, B, F, G... lol I am sure you get what I mean!

                          http://www.digikey.com/scripts/DkSea...?KeywordSearch
                          2003 Chevy Tahoe Z71
                          STOLEN - M10000, 512MB, 60GB 2.5" HDD, 7" Custom mounted Lilliput, Morex 3688 Case, 90W PSU w/ ITPS, GPS & CD-RW/DVD. New parts ordered for the next generation!

                          Comment


                          • #14
                            Look in the data sheet. The different letters correspond to different packaging. I used a PT6653D type. It lays flat and has hole through pins. Also the 665x series can be had a bit cheaper (cough), if you know what I mean.

                            Originally posted by nirvanades
                            Why does the linear chip create more heat?
                            Linear regulators act like a current controlled resistor in a circuit (i.e. a transistor). As such the current going into them is the same as that going out. The extra power (Vi-Vo)I is dissipated within the chip as heat. In your case you want (14.4V - 5V)*3A = ~25W.

                            The TI chip is a switching (buck) regulator. It switches the input power on/off rapidly through an inductive/capacitive network. The rate of switching controls output voltage. Because the active components are used primarily in saturation (instead of their linear region), there is very little voltage drop across them and thus much less power is wasted as heat.

                            Mr. P. or Mastero can almost certainly give a better explanation of this than I just have.
                            2004 4runner

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                            • #15
                              Cool - That makes total sense from everything I have been reading! Thanks
                              2003 Chevy Tahoe Z71
                              STOLEN - M10000, 512MB, 60GB 2.5" HDD, 7" Custom mounted Lilliput, Morex 3688 Case, 90W PSU w/ ITPS, GPS & CD-RW/DVD. New parts ordered for the next generation!

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