My first PCB

Discussion in 'General Electronics Chat' started by R!f@@, May 12, 2011.

  1. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    Hey Guys.

    Finally I manage to draw a PCB board in Eagle. :D

    This drawing thing is not easy I must say, I took 12Hrs :eek: & I never realized that until I looked at the clock.

    I leaned how a schema should be routed in order to compact the PCB size. It is not always the way u want unless u have both apps running and make changes.

    Good think I got dual monitors. In one I can correct schema and I can see the board routing changes from the other

    The board is for the 4 digit voltmeter I am making, I do not have the CC 7 segs, so I have to make changes to drive the CA segments. Changing the code confuses me, so until I learn to handle the code this is the way for me to go & finish this quickly.

    Since I cannot find DIP's, I a trying to make a SOIC to DIP adapter for the inverter IC's I had.

    I do not have a laser jet so I will be going out somewhere to print it. I made the Wax paper as Bill suggested.

    Wish me luck, will post once I got the print onto the wax.

    {ed}
    Much thanks to Bill for the Wax paper.
     
  2. Wendy

    Moderator

    Mar 24, 2008
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    Have you figured out how to do the transfer? That has been my big problem until I got the laminator. I'm still looking for a couple of pieces of smooth thick aluminum plates to try an alternate technique, using the oven. I suspect the laminators days are numbered, it doesn't go as well as I like (though it works OK).
     
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    That should work, but its a lot of work just for an adapter.

    Got EBay? I use a lot of adapters for my breadboards as I actually prefer to work in SMD parts. Dig-ole has been my source for these types of adapters as they are incredibly inexpensive and surprisingly good quality with plated thru holes and gold plating.

    They work hard at getting two patterns per board too. The link below (I believe it fits your part) is useful for 14-20 pin devices, either the SO or SOP outline

    However, good fast and cheap don't mix so while they are good and cheap you ain't getting them fast; the standard shipping for 1 part covers everything you order but it can take 3-4 weeks to see your stuff. I keep a stock on hand so I don't mind. You'll be long done with your PCB before these come but you may want to get some for the next project.

    Hey, I'm almost out of 8-pin adapters. I better order some while I think of it.

    http://cgi.ebay.com/2PK-SO-SOP-SOIC...633?pt=LH_DefaultDomain_0&hash=item3a6041fd79
     
  4. Markd77

    Senior Member

    Sep 7, 2009
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    Those traces are a bit thin, they could get etched through. Better to make them too thick than too thin because you can always cut away a few shorts with a scalpel.

    For my display:
    http://forum.allaboutcircuits.com/showpost.php?p=342284&postcount=797
    to change to common anode displays:
    swap the NPNs for PNP transistors,
    in the ISR change all lines like this:
    bcf PORTAtemp, 7
    bsf PORTAtemp, 2
    to
    bsf PORTAtemp, 7
    bcf PORTAtemp, 2
    which will deal with the transistors.

    In the lookup table invert all the bits (although you might have to recalculate the table if your display pinout / schematic doesn't match mine.

    Also change this line

    bsf maxdigit2pins, 2 ;decimal point
    to
    bcf maxdigit2pins, 2 ;decimal point

    I think that should be most of the way to getting it working.
     
    Last edited: May 12, 2011
  5. t06afre

    AAC Fanatic!

    May 11, 2009
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    On DIY PCB thin tracks can be a nightmare. Keep then as wide as possible. On this board you have more than enough space. By the way is the phone number yours ;)
     
  6. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    thanks guys....

    It was more of a learning thing.

    @ Mark, let me see if the code change works.
    and yes that is my cell no.
     
  7. t06afre

    AAC Fanatic!

    May 11, 2009
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    Will you be doing much PCB work. I can recommend some some books if you want....
     
  8. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    I will in due time. Once I get the hang of it, I bet I will be doing a lot more.
    Recommend away :)

    By the way, what is the recommended sizes for traces for Signal purposes.
    What sizes are you guys using.

    I think I used 0.01. Which is the minimum size in eagle.

    Are you guys saying that I use the IC pin pad size for traces too?
     
    Last edited: May 12, 2011
  9. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    OK.. I have increased the signal wires from 0.01 to 0.016 mil
    This is the best I could do to keep the tracks from overlapping or coming too close to each other.

    The power tracks are 0.024 mil.

    Do you think I should increase it more?

    When I move them the wires jumps too much, I cannot move it by a little amount. Is this a grid size related issue.
    If not, how can I move the trace to places I want.

    One more thing, can anybody tell me how I can set a default size before routing so that I do not have to resize each trace one by one.

    And what are the recommended sizes for signal and power traces. Is there any table to show the current capacity and break down voltage, i.e. How close two traces should be for a given voltage level.
     
    Last edited: May 12, 2011
  10. Markd77

    Senior Member

    Sep 7, 2009
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    Much better, I'd be tempted to move the trace running under the chip closer to the center. There's a slight danger of bridging the gap when you solder the SOIC.
     
  11. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    Corrected. I thought of that too before.
     
  12. nbw

    Member

    May 8, 2011
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    Not a bad first attempt. You'll have tons of fun creating others. I often have to stop and remind myself if designing the PCB straightaway (only simple ones) that placement is reversed - so pin1 on an 8-pin is reversed!

    I used the print-'n'-peel method; I've got the technique sorted out now where I can get 0.25mm traces coming out nice and clear.

    All the best!
    Barney Ohmart
     
  13. t06afre

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    May 11, 2009
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    A problem with DIY PCB boards, and thin tracks. Are that thin tracks very easy may become unglued. Then doing rework on the board. I would perhaps say 15 mil track is the lowest you can go. But this will depend on many factors. Like the board quality, the etchant, the lightbox used, your skills and so on.
     
  14. Markd77

    Senior Member

    Sep 7, 2009
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    I'll have a look at the code soon to see what changes need making for common anode. Are you not using the buttons at all on your version?
    How's the etching going?
     
  15. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    Thanks all,
    Specially t06afre, bill and Mark.

    I am making all the PCB layout that I need so that I have plenty to experiment. I have only 2 clad boards.
    I need to buy more to proceed.

    Have yet to decided how to transfer as there are plenty of methods. I think I will have to make a UV transfer box.

    Mark. I will have the code a go soon.

    I have to take some time off for the workload.

    will keep u guys posted.
     
  16. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    All need is 4 digits like this 00.00, No dp Switching as it will be fixed.
    My supply is from 00.00V to 40.00V, I need 10mV resolution.

    as I will use voltage settings like that changes from 0.01V increments.

    I will use only for digits and RA0 as the ADC input. No other use for now.
    No min, max or hold or anything fancy, as this will end up as a voltage meter in the PSU.
     
  17. Markd77

    Senior Member

    Sep 7, 2009
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    I'll have a look today.
    At a range of 40 volts it only has a real resolution of 40mV because the ADC is 10 bit (1024 steps) and 40V/1024 ~= 40mV
    However it averages so the display changes in 10mV increments and any ripple or noise will increase the resolution.
     
  18. t06afre

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    Mark what is this little side discussion between you and R!f@@ ;) I feel left out
     
  19. magnet18

    Senior Member

    Dec 22, 2010
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    Well done!
    I need to get some double sided for that darn clock...
    I would prank call you... but it might break my bank account... ;)
     
  20. Markd77

    Senior Member

    Sep 7, 2009
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