I want a review on my project.

Discussion in 'The Projects Forum' started by imraneesa, Jan 28, 2015.

  1. imraneesa

    Thread Starter Member

    Dec 18, 2014
    184
    4
    Please review this project and tell me if I can proceed for the pcb. your advice will be highly appreciated. thank you.
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,979
    744
    Can't open your files...
     
  3. imraneesa

    Thread Starter Member

    Dec 18, 2014
    184
    4
     
  4. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,287
    1,252
    Convert your files to .png files. Then upload that.
     
    simo_x likes this.
  5. Reloadron

    Active Member

    Jan 15, 2015
    963
    232
    You are posting your files in .sch (schematic) formats and a .zip file containing files that go with the software you created the files in. Unless people can open the files they are useless. It's like me posting a .pdf file and nobody has Acrobat Reader to open the files. For a schematic save the file to maybe a graphics format like .jpg or .png ad then post it.

    Ron
     
  6. imraneesa

    Thread Starter Member

    Dec 18, 2014
    184
    4
    how to do that. I cant upload brd file. and if I print screen and save it as png. you cant see the details in eagle. so how to do the upload. I am confused.
     
  7. imraneesa

    Thread Starter Member

    Dec 18, 2014
    184
    4
    here is the schematic. and how to upload the eagle brd file now.
     
  8. imraneesa

    Thread Starter Member

    Dec 18, 2014
    184
    4
    here is just the png of brd.
     
    • brd.png
      brd.png
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  9. imraneesa

    Thread Starter Member

    Dec 18, 2014
    184
    4
    all the files I uploaded before were Zip files. so it need Zip software to open them. but there is no way I can upload brd file. I don't know what to do.
     
  10. Reloadron

    Active Member

    Jan 15, 2015
    963
    232
    Your voltage regulator schematic looks fine from what I can see. No details like supply voltage and out voltage.

    Ron
     
  11. Reloadron

    Active Member

    Jan 15, 2015
    963
    232
    OK, I think you are doing this in Eagle. Should that be correct here is what you can do. Open your .sch (schematic) file in Eagle. From File on the top choose Export and then Image from the Export options. In the Export Image dialog box check Clipboard and then OK. The image has been saved to the clipboard. Have Microsoft Paint open, Microsoft Paint is a general Windows program, any photoshop program will work. In MS Paint choose Edit and Paste. Your schematic image is now in MS Paint. Choose File and Save As and select to save the image as a .png file. You can do the same with your other files. That should help.

    Ron
     
  12. LDC3

    Active Member

    Apr 27, 2013
    920
    160
    I believe there should be a line from the Adj pin to ground (it's missing in your schematic).
     
  13. Reloadron

    Active Member

    Jan 15, 2015
    963
    232
    Yeah, something isn't right with your adjust pin. What exactly is that regulator?

    Ron
     
  14. Mogens Dreier

    New Member

    Jan 28, 2015
    1
    0
    Change your grid to 1,27mm. In sch use the ERC button.
    HTH
    Mogens
     
  15. imraneesa

    Thread Starter Member

    Dec 18, 2014
    184
    4
    It is a constant current regulator for laser diode.
     
  16. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,979
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    If its a constant current regulator,your output should be taken from the adjust pin.
     
  17. imraneesa

    Thread Starter Member

    Dec 18, 2014
    184
    4
    Supply is 8.4v and the output I need is 5v. Using 3ohm resistor to give constant current of 400mA. Capacitors iam using 42uf.
     
  18. LDC3

    Active Member

    Apr 27, 2013
    920
    160
    This is the usual way to make a constant current source from a voltage regulator:
    [​IMG]
     
    Last edited: Jan 29, 2015
  19. imraneesa

    Thread Starter Member

    Dec 18, 2014
    184
    4
    I added diode as reverse polarity protection. And capacitors to smoothen. 10uf on both input and output.
     
  20. Evil Lurker

    Member

    Aug 25, 2011
    117
    23
    While the LD1117-ADJ is the chip to use, your board layout is incredibly awful. The most glaringly horrid mistake of all is you have mounted an undersized SMD current limiting resistor immediately underneath the part of the regulator's mounting tab on the opposite side of the board. What are you trying to do, cook your poor regulator to death? You should have NOTHING under that chip other than a copper pour and thermal vias. Next off are the circuit traces which are far too thin for power applications. Then there is the output capacitor and reverse protection diode. You do NOT want to have a cap on the output of a constant current regulator for two reasons. First it throws the feedback compensation loop off potentially resulting in the regulator oscillating and second, the first time your laser diode gets disconnected either through manually tinkering with it or a transient bad wiring connections the diode will let out the magic smoke. Why? As soon as you take the load off a constant current regulator the voltage on the output shoots up, charging up the cap on the output, and as soon as that diode is reconnected your constant current regulator will become a capacitive discharge diode fryer. That said, since you shouldn't have a cap on the output there is no need for a reverse protection diode. Finally your layout is asking for potential ground loop issues.

    If it were me, I'd use the low dropout regulator, a good 50v rated 10uF XR7 MLCC cap or maybe tantalum, ditch the tactile switch in favor of a latching push button DPDT, and maybe even set up some sort of DIP switch array so I can set my output current as at the current your intending to push will exceed the maximum wattage ratings of most trim pots. I might even go so far as to put a semi-high value bleed down resistor in parallel with the input cap to make sure the regulator quickly completely powers down when you switch it off.
     
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