Off-Topic Anyone with PCB design experience?

Discussion in 'Off-Topic Chat' started by bijomaru, Wednesday 15th Aug, 2012.

  1. bijomaru Premium Member Club Supporter

    United Kingdom Rob Swindon
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    I am trying to design relatively simple PCB to power up few LEDs for the PC case I am doing.

    I've managed to design and test in some software the circuit, and it does what I want it to do. But I'd like someone with experience to check it over for me if possible. I don't want to burn down the house, or the PC when I fit it and it turns out I've missed something obvious :Smile:

    I will post the design here with questions if someone is willing to take a look.
     
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  2. Ichiban Founder Staff Team

    England CJ Leeds
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    That is right up I-S street he the wizz kid on PCB , I have not seen him for yonks on here thou. PM him bud he will know all your answers.

    Of someone with experience can assist here..Stick up the diagram let have a look even i could give me two p:Foolish:
     
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  3. bijomaru Premium Member Club Supporter

    United Kingdom Rob Swindon
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    Ok. So basically this is my first PCB ever but it's fairly simple so with some 'wiki' etc knowledge I've managed to figure out I need diodes.

    :Whistle:

    Here's the layout:

    pcb.

    :Whistle:

    So what it does, at the bottom there will be 3 LEDs connected (Red, Green, Blue) which are getting +5V from the standard PC molex cable. Then at the top of the circuit, each of the 7 connection points will be connected to a rotary switch. So for example if I select pos.1 on the switch, the current start flowing from RED LED to R at the top, only switching on the red led. If I put in pos.2, it will go from RED LED and GREEN LED to RG at the top. At this point I understand I need diodes to make sure no other part of the circuit becomes active, thus switching on the BLUE LED which at this selection is undesirable.

    I've tested it in TINA software and some online flash animation, and the selections work ok, with no unwanted LEDs being powered when they should not be.

    :SOS:

    1. My main concern is, do I need any more stuff on here like resistors. Computer's power supply gives +5V on one of the wires, but can the amperage be too high and destroy the diodes/LEDs?

    2. Also I've joined some circuits where they run along to minimise the amount of them. Example: In my first try from RED LED there were 4 separate lines towards R, RG, RB, and W. Now I've minimised it as essentially RB and W run in the same direction so can run as one only to split where they need to. Same for circuits behind the diodes, they're merged if running towards the same point, i.e. circuits running to GB from 2 diodes below. Is that practice acceptable or should I keep a separate circuit for each point-to-point connection?

    Hope any of that makes sense :Smile: Like I say it's my first PCB so I might not be describing stuff properly. But it's a fairly simple concept so I hope someone can spot if there's anything obvious missing.

    :Hey:
     
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  4. SpeedyGee Administrator Staff Team

    England Speedy Birmingham
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    Yes you need some resistors to limit the current going through the LEDs. Without these your LEDs would just overheat and burn out. You need to look at the spec of the LEDs and provide them with the current they need to run.

    Also in your case you need to stregically place the resistor for each LED combination ... by this I mean you need one for Red LED only, another for Red and Green in parallel etc etc ..

    This page can help you work out the value of the resistors.

    Does that make sense ?
     
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  5. bijomaru Premium Member Club Supporter

    United Kingdom Rob Swindon
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    It does. And I think I am sorted in that case, because the LEDs sit on a daughterboard that was in the case already. I managed to get them working by connecting it to 9V battery. There must be some resistors on the board already.

    I can only provide voltage to on of the cables. The. The three other regulate the LEDs switched. On depending which circuit I close with -.
     
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  6. bijomaru Premium Member Club Supporter

    United Kingdom Rob Swindon
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    LED strip at the top

    image.
     
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  7. bijomaru Premium Member Club Supporter

    United Kingdom Rob Swindon
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    Design printed ...
    IMAGE_FB0E01CD-6A87-4547-B72E-762B28ECF0C4.JPG

    .. etching kit bought ...
    IMAGE_890B84DE-FDC9-4DDB-BD4A-F8484B05BD22.JPG IMAGE_D6B41B1B-E1CE-49E3-9ABB-2F471C00F87B.JPG

    Getting it done this weekend.

    Will report back when it's working ... or when I've burnt down the house...
     
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  8. bijomaru Premium Member Club Supporter

    United Kingdom Rob Swindon
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    Finished board. Took me few tries to transfer the print onto the board, and this was the second board I etched, as I took one the first one out too early ...

    IMAGE_81249DB8-4183-406A-9AD9-E69009F9C42F.JPG

    Few imperfections but it works, so now needs to be drilled and have diodes fitted.

    So far pleased :Smile:
     
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    Ichiban likes this.
  9. SpeedyGee Administrator Staff Team

    England Speedy Birmingham
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    Yeah that's looking good. So how did you xfer from print to the board ? Do you have a UV light box ?
     
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  10. bijomaru Premium Member Club Supporter

    United Kingdom Rob Swindon
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    Nope, didn't need UV with this kit.

    I ironed the toner print onto the board. It's a bit tricky to get the whole print to transfer, not sure if it's because of the iron I've used, or the photo paper.

    When that's transferred, I've used a CD permanent marker to fix bits that were missing.

    IMAGE_D3C64DEB-6897-450C-B53F-2D46B463D91C.JPG > after touching up IMAGE_C598A45E-943C-4A4C-9797-A45EBA3CC5F5.JPG

    Then just stick it to the Sodium persulfate bath prepared from warm water and the powder provided. I kept it in a sink, topping the sink up with warm water every 20 minutes or so, to keep the tray with the board warm. Apparently it speeds it up a lot.

    After about an hour the copper started to come off.
    IMAGE_98CEFD90-6DC2-4661-80D6-CC4ADFF62A23.JPG

    Half an hour later:
    IMAGE_BD62BCFD-C0DD-4AD8-B8F5-160E9BBE634C.JPG

    Then I just use kitchen sponge, the rough side, to get the toner and marker pen off.

    :Smile:
     
    Last edited: Monday 20th Aug, 2012
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  11. Jon_G Guest

    I'm impressed that the permanent marker protected ok against the etch - I don't think this would have worked in the days of using ferric chloride!
     
  12. SpeedyGee Administrator Staff Team

    England Speedy Birmingham
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    Permanent marker works fine with FeCl3.
     
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  13. SpeedyGee Administrator Staff Team

    England Speedy Birmingham
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    Have you tried using a laminator instead of an iron ?
     
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  14. SayamaAccord Top Contributor ★ ★ ★ ★ ☆

    Superb work, and great that members can help each other out like this.
     
    Ichiban likes this.
  15. bijomaru Premium Member Club Supporter

    United Kingdom Rob Swindon
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    Nope, tried only the ironing method. As this was a one time job, I'm not sure when will I be doing this again. Unless I mess up drilling the board and will have to do it all over again :Smile:
     
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  16. Jon_G Guest

    Now that you've had a go at making a PCB from scratch, it might be easier to use veroboard next time.
     
  17. bijomaru Premium Member Club Supporter

    United Kingdom Rob Swindon
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    Never heard about it before, but just googled it and it seems like a great way to test designs as well. Thanks!
     
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  18. Ichiban Founder Staff Team

    England CJ Leeds
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    Rob any updates on this buddy?
     
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  19. bijomaru Premium Member Club Supporter

    United Kingdom Rob Swindon
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    Sorry, been busy recently and forgot all about it ...

    With the long weekend coming I am hoping to make some progress and get this project rolling again.

    Last few weeks we've only managed to solder on the diodes onto the board. Need to come up with a solution for mounting the PCB in the case and best way to wire the LEDs not to obstruct drive bays, etc. Will post a quick pic later when I get back home
     
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  20. SpeedyGee Administrator Staff Team

    England Speedy Birmingham
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    :Need Pics:

    (sorry just had to drop one in there :Smile:)