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12V to 5V step down regulator VS. Switching regulator.

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  • 12V to 5V step down regulator VS. Switching regulator.

    I have been wanting to test my setup but can't until I have the KVMP switches powered on external power.

    In the past I had two different devices brought to my attention.

    The first is this one. Its a 12V to 5V step down regulator. What I like about this one is that for my install I will only need one. Its rated at 20A and I need 16A.

    http://www.current-logic.com/shop/in...products_id=14


    Then there is a switching regulator.

    http://www.jameco.com/webapp/wcs/sto...0001_212549_-1


    Now my understanding is that the step down regulator lowers the voltage in the form of heat. Are there any other disadvantages to it? How is reliability? A thing I do like is that I would only need one of these and its only about 39.99 after shipping.

    As far as the switching regulator, it puts out less amps, so I would have to buy 2 of them, which is more expense. I wonder though if the switching regulator is better then the step down regulator.

    So I guess the question is, which is better?
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  • #2
    I think what you are referring to as a step down regulator is actually a linear regulator. Basically, it reduces voltage through resistance, hence the reason it generates heat. As you can imagine, that heat is what makes them inefficient.

    I don't have any experience using a linear regulator for that much amperage but if I had to guess, it is going to get HOT. Like fry-an-egg hot.

    A switching regulator will be more efficent and run much cooler. If it were me, I'd go with the switching regulator, even if you need two.

    Are these for USB hubs in your install?
    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.
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    • #3
      Originally posted by Bugbyte View Post
      I think what you are referring to as a step down regulator is actually a linear regulator. Basically, it reduces voltage through resistance, hence the reason it generates heat. As you can imagine, that heat is what makes them inefficient.

      I don't have any experience using a linear regulator for that much amperage but if I had to guess, it is going to get HOT. Like fry-an-egg hot.

      A switching regulator will be more efficent and run much cooler. If it were me, I'd go with the switching regulator, even if you need two.

      Are these for USB hubs in your install?
      No, I have 6 hubs total, but only 3 need to be powered. The Rear PC is powering its own hub, via the OPUS 320. The other 2 hubs are being powered by a 15W OPUS PSU (5V 3A).

      The problem is the KVMP switches. They use 2.6A each. Basically the KVMPs can be powered via USB, but they would have to get it from both PC units, which will strain the PSU. So I have to power them external to keep the PC running good.

      If I want to be exact, the KVMPs will use a total of 15.2A. Before I needed 20 something amps, but I managed to get the rear system to power Ethernet switch and Access Point also. I may be able to use a PSU.
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      • #4
        In fact, a PSU might be a better route. I am sure the KVMPs dont use 2.6A all the time. Reason being is that I can use the 12V side of the PSU to power all my 12V fans. That will take some load off both the OPUS 320 and OPUS 360. My understanding is that fans can use upwards of 11W and I'd rather have my PSU keep that 11W. It would be more expensive, but I would have 12V and 5V regulation.
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        • #5
          Could also use an inverter. If I am reading this right (Bing), I take the Volts x Amps = Watts. What am I using though? The adapters are for 12V but they put out 5V. Because if I use 5V, all I need is a 100W supply. If I use the 12V number, I need a 200W supply. If I go the inverter route, I can use the original adapters and inverters are easy to get. Seems both the otehr items have to be ordered from China.

          Plus get maybe a 400 watt unit instead of the 200 watt so if anyone wants to use a video game console in the car.
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          • #6
            What is a kvmp? I know what a kvm is...

            I think you need to use the 5 volt figure for your calculation. The 12 volt is just the adaptor input voltage. The output is what you want to look at.

            5V X 2.6amps = 13 watts
            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?
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            • #7
              Originally posted by Bugbyte View Post
              What is a kvmp? I know what a kvm is...

              I think you need to use the 5 volt figure for your calculation. The 12 volt is just the adaptor input voltage. The output is what you want to look at.

              5V X 2.6amps = 13 watts
              A KVMP is a KVM that has a built in USB hub for peripherals. This is how I am sharing the touch screens between 2 computers. It also has sound switching so if the user wants to say watch a movie with everyone else on the 19 inch, they hit a command and the KVMP will allow them to see the PC2 on their screen, but keep the audio on PC1. These things are pretty cool. Without them my install would have been nothing.

              I think I will go the inverter route. The inverter would cover so much more. It would get the dumb KVMP switches out the way, and give me an outlet if anyone wants to use a house hold appliance like a video game system.

              Boy, I sure strayed far away from the regulator idea, lol.
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              • #8
                The Current Logic unit could actually be a switching type converter. It says 90% efficiency (if it were linear that number would be far far lower) and other similar units in its product line say they are "dc-dc converters" which essentially means the same as switching.

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                • #9
                  Originally posted by CanuckMark View Post
                  The Current Logic unit could actually be a switching type converter. It says 90% efficiency (if it were linear it would be far far less than that) and other similar units in its product line say they are "dc-dc converters" which essentially means the same as switching.
                  Thanx for that update.

                  I did change a few things. I may just go with the step down regulator. I do not trust the amperage the inverters claim to handle. It seems every site has a different amperage. I think i'll get the step down and call it a day.
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                  • #10
                    A linear is at least 60% inefficient - ie, 7/12 (7volt drop from 12V).
                    If running at 14.5V, its (14.5-5)/14.5 = 65% inefficient.

                    If it drops [email protected], that's 7x16 = 112W in heat.
                    If it's 14.5V hence dropping 9.5V to 5V is 9.5V x 16A = 152W of heat.
                    And the input current will be 16A to provide 5V @ 16A = 80W output.

                    Switching regulators can be 90% efficient - eg; if [email protected] = 87W input for [email protected] = 80W output => 80/87 = 92% efficiency.



                    PS - that linear converter is a "12V/24V to 5V, Step-down, 20A, 100W". I hope the 100W simply means its output, not its thermal rating. IE; [email protected] = 100W.
                    But max V-input if thermally limited to 100W is 10V for 20A, or (5 + 100W/16A) = (5+6.25) => 11.25V maximum for [email protected] output (as opposed to dropping 112W & 152W at 12V & 14.5V as above).

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                    • #11
                      Originally posted by OldSpark View Post
                      A linear is at least 60% inefficient - ie, 7/12 (7volt drop from 12V).
                      If running at 14.5V, its (14.5-5)/14.5 = 65% inefficient.

                      If it drops [email protected], that's 7x16 = 112W in heat.
                      If it's 14.5V hence dropping 9.5V to 5V is 9.5V x 16A = 152W of heat.
                      And the input current will be 16A to provide 5V @ 16A = 80W output.

                      Switching regulators can be 90% efficient - eg; if [email protected] = 87W input for [email protected] = 80W output => 80/87 = 92% efficiency.



                      PS - that linear converter is a "12V/24V to 5V, Step-down, 20A, 100W". I hope the 100W simply means its output, not its thermal rating. IE; [email protected] = 100W.
                      But max V-input if thermally limited to 100W is 10V for 20A, or (5 + 100W/16A) = (5+6.25) => 11.25V maximum for [email protected] output (as opposed to dropping 112W & 152W at 12V & 14.5V as above).
                      So if it was your install, which would you get? The Linear or the Switching Regulator? The heat is concerning me on the Linear. I am starting to lean more towards the Switching now because PaulF uses one and swears by it. I havent seen anyone use the Linear and maybe the heat issue is why. Ive already spent so much money on my install, no reason to be cheap now, I'll just spend the extra money!
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                      • #12
                        I'd get the Switching.
                        Else the switching.
                        Or at a pinch, the switching....

                        For small loads, linear is ok.
                        For big or otherwise, switching is preferred for efficiency, and often size.
                        Problem with switching is expense.
                        But those Mean Well switchers seem to be a very good price, and from what I hear, they are good & reliable.

                        Since the prices are so close in this case, switcher definitely.
                        Even at greater price differential, 100W of more of heat is a lot of heat; and wasted load (ie, equivalent to a pair of headlights...).


                        Just one thing - do NOT parallel PSUs - ie, don't connect two 10A linear OR switchers together to get 20A; keep them separate else buy the right size....

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                        • #13
                          HEHE, noooooooo, I wasnt going to do that. I was going to put three KVMPs and maybe the ethernet hub on one switch. Then three KVMPs and maybe the Access Point on the other. So one would be 9.8 amps in use, the other would be 9 amps. Thats going by the adapter brick numbers, it will most likely be less then that.
                          Nirwana Project, the Android/Win 7 hybrid system!

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                          4X MK808b
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                          3x 7 inch Screens
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                          • #14
                            I have a question though. I also have one USB hub that is on the OPUS 320. In the past the OPUS 320 would act funny with a USB hub. I would have to unplug the hub for the PC to boot correctly. Do you think it will do harm if I put the USB hub on one of the switching regulators and max it out to 10A?
                            Nirwana Project, the Android/Win 7 hybrid system!

                            1X Ainol Novo Flame Tab
                            4X MK808b
                            3x Perixx Touchpads
                            3x 7 inch Screens
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                            1x Win 7 PC

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                            • #15
                              I believe they are both switching power supplies.

                              Here is some math that applies to linear regulators.

                              (12V - 5V) x 20A = 140W wasted as heat
                              (14.4V - 5V) x 20A = 188W wasted as heat

                              The largest heatsink I could find on digikey is one that can dissipate roughly 50 watts of heat.


                              I was googling around for a +5V supply for my truck, and the best I could find was a BEC for RC radios and it had a rating of 10A for ~$38.

                              The one from Current-Logic can do 20A and is about $25 plus it is epoxy sealed and waterproof.

                              I plan to buy this and mount it in my dash and use it for projects (Arduino / AVR) and for charging my iPhone.

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