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Making use of 16 volt AC adapters

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    #1

    Making use of 16 volt AC adapters

    Hi Gang ,It has been awhile since I been on here to pick someones brain about somthing electronic.
    I got a nice buy on some 16 volt 7.5 amp AC to DC power supplies,better know as AC adapters.
    As we all know these "bricks" can be used for laptops, LCD panels and LCD TV sets. The thing is alot of them require 12 volt input, and 16 is somewhat on the high side and could overpower and prematurely toast some of the components inside. Some of the Dells and Samsung stuff are even 14 volt input .
    I would not be too afraid to use the 16 on the 14 volt units but the 12 volt ones is sort of pushing it to the limit.
    My question is: Does anyone know a way I could build (or where I can look for) a small voltage reducer to put between the power supply and the item to be powered ? I was hunting around on the net, but ran into alot of things that don't do exactly what I am looking to do.
    Thanks
    Dave
    Last edited by CudaDave70; 12-04-2008, 01:04 PM. Reason: correction
    I am pretty good at keeping a secret,it's the people I tell that can't keep their mouth shut!
    Tags: None
    #2
    Re: Making use of 16 volt AC adapters

    often the brick will have an adjust pot inside.
    hmmm 16v?
    ibm laptops.

    Comment

      #3
      Re: Making use of 16 volt AC adapters

      @ KC8: not every IBM, my Thinkpad 600 requires a 14.4 V tension.

      @ Cuda: open it and look for the potentiometer KC8 named. If you can't find it, why not connecting psu output to a transformer?

      Zandrax
      Have an happy life.

      Comment

        #4
        Re: Making use of 16 volt AC adapters

        Depending on the current draw you could externally wire up a linear regulator as well.
        Elements of the past and the future combining to make something not quite as good as either.

        Comment

          #5
          Re: Making use of 16 volt AC adapters

          Hey Guys ,thanks for the info ,I love the idea of being able to adjust the voltage I did not know there was a pot in there for that reason .
          Trying to open up one of these can be a disaster like sticking a screwdriver in your hand . I have tried this before ,hurts like hell .Too bad they didn't use a few tamperproof screws instead of that glue .I will try that with one and see if I can do it,maybe they were stingy with the glue on these .
          I would like to try to make a small converter that I can plug this 16 volt supply (it has a 4 hole plug) into an have a way to set it to whatever voltage needed and also have assorted plugs so you could use these on many other different applications. I don't really know where to start to figure out what I need to do this,is there somewhere I could find a schematic for one .Could someone aim me in the right direction where to locate such things as this . I have quite a few of these and want to make good use of them they are pretty heavy duty looking units and probably well made .
          Thanks
          Dave
          I am pretty good at keeping a secret,it's the people I tell that can't keep their mouth shut!

          Comment

            #6
            Re: Making use of 16 volt AC adapters

            Hi CudaDave70

            your question is similar to this one .
            If I were you I will build some step down regulator, there are a lot of dedicated IC today and it is not too complicated, you need some components.

            You can try to ask for demo board to some Chip manufacturers (TI, Maxim, National,...); here in Italy my company has a good relationship with STM , very often they give us demo boards for free as we are a customers for them, I don't know if they give free samples to private.

            For the AC/DC adapter, I think you will not find a potentiometer inside, they usually use fixed resistor for voltage feedback.
            Moreover even if you change the voltage feedback, the PSU probably will have problem to decrease so much the voltage 16V-->12V

            You can't follow zandrax's suggestion because the output is DC not AC.

            Linear regulators need big heatsinks: for a 12V 1A you waste 4W with input voltage of 16V and if you need more current you waste more energy.

            The only thing IMO is step down regulator to use these adapters on appliances with lower voltage unless you need low current on a voltage not very lower compared to 16V, in this case you can look for LDO - VLDO Regulators.

            Ciao
            Gianni
            Last edited by Gianni; 12-05-2008, 07:57 AM. Reason: Typo
            "In the confrontation between the stream and the rock, the stream always wins...Not through strength, but through persistence."
            H. J. Brown

            Comment

              #7
              Re: Making use of 16 volt AC adapters

              A switching regulator would generate much less heat but they need a stoarage inductor. The datasheet for the IC should tell you how to wire them up.

              http://www.rason.org/Projects/swregdes/swregdes.htm

              To open them is easy just buy a block plane refill from your local home improvement store. Insert it between the case halves and whack it with a hammer.

              KC uses a cheap flea market knife and the hammer both work well because the thin blade fits between the case halves.
              Last edited by Krankshaft; 12-05-2008, 09:57 AM.
              Elements of the past and the future combining to make something not quite as good as either.

              Comment

                #8
                Re: Making use of 16 volt AC adapters

                I'm no expert in electronics, but I just got this random idea from cheap, group-regulated computer PSUs. You know how for the +3.3v line they usually have one side from the +5v transformer output that goes through a saturating coil which reduces the voltage and then goes to the +3.3v schottky while the other one goes directly to other side of the +3.3v schottky - well could that idea be used here (provided that the power brick is a SMPS)?

                Comment

                  #9
                  Re: Making use of 16 volt AC adapters

                  Well I got alot of different ideas coming in, all are interesting and I thank those who offer suggestions I was able to open it up ,there were 4 screws hidden under the little rubber pads so I was able to look inside . I did locate what appeared to be a pot on the under side I tweaked it and it did nothing with the voltage. It never moved from 16.4 volts. So I am going to try some of the other ideas suggested . I will check back later
                  Thanks Guys
                  Dave
                  I am pretty good at keeping a secret,it's the people I tell that can't keep their mouth shut!

                  Comment

                    #10
                    Re: Making use of 16 volt AC adapters

                    Question: Is your adaptor of the switching type,or a simple transformer and diode bridge type? The switching type is of course regulated,and you can drop its voltage output by inserting ordinary diodes of the correct current rating in one of the leads. Each silicon diode has a constant voltage drop of 0.6 volt (regardless of current drawn,within a reasonable range of course),so 7diodes in series will give you 4.2 volts drop. Your 16.4 volts output will change to 12.2 volts. Hint: if your power adaptor is rated over 100 - 240 volts,the unit is of the switching type.

                    If your adaptor is of the transformer type, then you are out of luck. These types are usually not regulated,and the output voltage swings over a wide margin,depending on current draw of the device you use it on.
                    Last edited by berniedd; 12-07-2008, 08:14 AM.

                    Comment

                      #11
                      Re: Making use of 16 volt AC adapters

                      I am pretty sure it is a switching type. It does have a transformer inside though. It is like you would use on a laptop or LCD monitor. Is it a possibility to put 4 diodes in a series in the positive lead and the other 3 on the negative side wire . Would that work that way or am I way off base on that .
                      The current draw of most monitors is normally rated around 3 amps but I have this one that is rated about 6 amps,it is alot bigger and heavier .I really doubt if it ever demands that much current,maybe when you first light it up. Is this what they call zener diodes?
                      I am pretty good at keeping a secret,it's the people I tell that can't keep their mouth shut!

                      Comment

                        #12
                        Re: Making use of 16 volt AC adapters

                        Yes, it won't matter if 4 diodes are in one lead and 3 diodes are in the other lead. Just make sure they are connected in the correct orientation,so that all diodes are in the forward conducting direction. Make sure the diodes are rated at least 5 amperes each.

                        And no, you don't want the zener kind of diodes.

                        Comment

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