Variable bench supply project - comments?

Discussion in 'The Projects Forum' started by marshallf3, Apr 27, 2011.

  1. marshallf3

    Thread Starter Well-Known Member

    Jul 26, 2010
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    Decided I needed another bench supply for home and whipped this design up using their examples as a reference, looking for comments. With the right transformer it's easily capable of 1.2V - 36V @ 5A, it also has the option of adding a variable current limit simply by replacing a single resistor with a single pot. Very minimal component count.

    National will sample the IC to you for free - you pay the postage if you're not a registered business with a business e-mail address or it's totally free if you do.

    I've included the schematic and a bill of materials which is somewhat flexible.

    http://www.innoengr.com/forum_projects/bench_top_supply.jpg
    http://www.innoengr.com/forum_projects/supplyBOM.xls
     
  2. BillO

    Well-Known Member

    Nov 24, 2008
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    I can't see anything immediately obvious except that at 24v and 5 amps you might loose some regulation due to R2, but I've not done the math. Also, I'd suggest a big heatsink and a fan to get the most out of it.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    It is preferable to use .png files for schematics, as they are not "lossy" like .jpg files are.

    Many people won't have Microsoft Excel, so won't be able to see your spreadsheet.
    If they are running a Windows platform, they may be able to download/install the Microsoft Excel Viewer:
    http://www.microsoft.com/downloads/...F9-CE06-4E1C-8DCF-F33F669DBC3A&displaylang=en
    but those running other OS'es will be out of luck.
    Consider posting a .txt file that has tab separated values.
     
  4. marshallf3

    Thread Starter Well-Known Member

    Jul 26, 2010
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    R2 is not essential or can be changed to a far lower value, at present it would drop 0.5V at 5A so I may have specified too high a value or should have just left it off.

    The thing is I've always liked to very slightly buffer the voltage from a rectifier section to the filter cap if it's a large cap. When you first turn the thing on that 4,700 uF cap is like a dead short and puts a very large surge current on the rectifier. Guess I'll change tht to a 0.05 or less as it would still serve the same purpose.

    What surprised me is how low of a component count one could achieve building a decent amperage variable switched supply. Getting the IC for free (they'll send you up to 5) is a great deal too. The biggest limiting factor would be if you had to buy the transformer. Then again there are some good deals on surplus transformers running around or you could get lucky like I did and already have one, it came out of an old satellite positioner arm driver box.

    In other words if you've got any satellite dealers that have ben in business since the days of the 10' dishes they may have a junk pile of those old boxes stashed away in their junk pile.

    Here's a half decent deal if you didn't need to go much above 12V: http://www.goldmine-elec-products.com/prodinfo.asp?number=G17913

    Unfortunately I don't have any software to create or convert to .png files, guess I should update my Photoshop (need to anyway) or find some free converter download software as my schematic program will only export drawings as .bmp or .jpg
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    While in your schematic program, you can just do a Ctrl+PrintScreen to capture the image in a buffer, and then paste it into MS Paint, and save it as a .png file.
     
  6. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
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    Typical Excel spreadsheets that don't use fancy plug-ins or macros can almost always be opened up in Open Office. I've done it many times on Windows and Linux and I can't recall any spreadsheet that I had lots of trouble with. Of course, macros don't transfer over.

    IrfanView is free and can do the conversion (as well as batch conversions). It's a good tool I've been using since the late 90's.
     
  7. marshallf3

    Thread Starter Well-Known Member

    Jul 26, 2010
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    I can open the .jpg in IrfanView but can't find any way to save it as a .png
     
  8. Wendy

    Moderator

    Mar 24, 2008
    20,765
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    If you are using WinXP then M/S Paint will do it off the shelf. You have to go back to Win98SE to not have .png.

    Since I am using a work computer I don't like to go to off site hosting for a picture, expecially since AAC can do the same thing on site with no ads.
     
  9. marshallf3

    Thread Starter Well-Known Member

    Jul 26, 2010
    2,358
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    Well, there shouldn't be any ads when the images are on my website.
    I can get a much newer copy of Photoshop next week, I really need to upgrade as mine is from back in the Win95 era. Didn't bother me as I rarely use it.

    I don't know how to load attachments in AAC, I also don't know if it would take an .xls or other spreadsheet file that I list the bill of matrials on.

    Think this is good enough to submit to the The Completed Projects Collection and, if so, how do you go about that?
     
  10. Wendy

    Moderator

    Mar 24, 2008
    20,765
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    Write it up completely, and include all the attachments. Try to treat like the set of plans it is, and try to anticipate all the questions.

    To load attachments, click <Go Advanced>, <Manage Attachments>, then follow instructions. It is very easy.

    To display them as part of the post, insert the internet address on the address bar (while full size) and put it between the VBulliten LaTeX, {img}internet address{/img}, the {} being square brackets [].

    How to Display Attachments Full Size
     
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