Project: Variable Power Supply Using the LM338

Discussion in 'The Projects Forum' started by ELECTRONERD, Dec 31, 2009.

  1. ELECTRONERD

    Thread Starter Senior Member

    May 26, 2009
    1,146
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    Hey Everyone,

    I just recently completed this variable power supply and thought you guys would like to look at it. For pics and details visit this link:

    http://electrobird.net/Analog Projects/Variable PSU.html

    I finally gave up batteries; they wear out too rapidly and they can only provide 25mA max!

    Austin
     
    Last edited: Jan 2, 2010
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Glad you managed to complete your power supply, Austin.

    However, you give absolutely no details on how to go about duplicating your supply, only some minor details about the completed supply.

    If you wish to be considered successful on your project, you will need to provide all of the details necessary to successfully replicate your project. You must assume that the reader of your project has very limited exposure to electronics.
     
  3. spinnaker

    AAC Fanatic!

    Oct 29, 2009
    4,884
    1,004
    Yes, I am a noob. And I would like to see at least some detail.


    • How you laid out the board. I don't even see it in there. It must me small!. :)
    • How you built the project box. Or did you buy one?

    Yeah documentation is the most boring part of the project. :)
     
  4. Ante

    New Member

    Dec 25, 2009
    10
    1
    The circuit might originate from the LM338 datasheet. Looks like this bench PSU project has an onboard wallwart to supply the voltage display.
     
  5. ELECTRONERD

    Thread Starter Senior Member

    May 26, 2009
    1,146
    16
    I apologize for not adding the schematic earlier, but it is now shown in the first post. In addition to the schematic from the LM338 datasheet, I also added some circuitry as well; particularly for the voltmeter display.

    Austin
     
  6. ELECTRONERD

    Thread Starter Senior Member

    May 26, 2009
    1,146
    16
    My PCB board is located to the top left corner with the two big caps on it. My display circuit I just soldered with out a PCB since the total quantity of parts were very few.

    I was given the project enclosure by my generous amateur radio group. Project boxes are so expensive these days so I was lucky to receive it. It already had some circuitry inside, so I quickly dissassembled everything and got to work! ;) What the preceding circuitry was meant for is tentative to me but I think it involved the computer in order to operate.

    I'm glad that people are interested!

    Austin
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    You have to document everything on your site.

    If you don't, you'll continue to get such questions.

    It's a pain, but otherwise you'll not get beyond it - you'll be too busy answering questions about that project instead of subsequent projects.

    Build a solid foundation. Then make progress based on that foundation.
     
  8. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    How did you make the PCB?
     
  9. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    See what I mean? ;)
     
  10. t06afre

    AAC Fanatic!

    May 11, 2009
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    I can see some details worth mentioning.
    1) You have no Strain relief for the mains input cable, and the cable are in direct contact with the metal housing. This is potentially hazardous as the sharp edges in the drill hole can chew through the cable insulation very quickly. Also it is a no-no not having strain relief for the mains cable. I guess you understand why.
    2) I also do not like the way you have bundled together The cables from the primary and secondary side of the transformer. They should be kept apart. To be honest your cabling is somewhat messy(bird nest). Your design would be more cleaner if you move the mains switch to the back of your housing. You should be more consistent and separate your housing in a primary and secondary side with respect to the transformers. You have the space and it would clean up the design and make it safer.
    3) I can not see any fuses in your schematics
    I suggest you temporarily remove your project until you have modified your design. Because now it is not worth sharing on the web. But if it is some comfort to you. My first design attempt looked very much like yours. It is a learning process we all have to go through ;)
     
  11. ELECTRONERD

    Thread Starter Senior Member

    May 26, 2009
    1,146
    16
    Excellent! Thank you all for the comments, questions, and tips!

    @ SgtWookie: I now realize the importance of documenting my projects, and will start doing it from now on. I will work on that and post my results soon.

    @ t06afre: I actually did modify my project since the website pics. I added a fuse, strain, and knob to the PSU. I will seperate the primary and secondary side of the transformer immediately.

    Things to look foreward to: A documentation of my PSU and new pics!

    I trust that you all will acknowledge my documentation and note what I should improve on and what I should add to it.

    Thanks,

    Austin
     
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