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pcb artwork, traces and gnd plane

Discussion in 'PCB Layout, Design and Manufacture' started by DuctDuck, May 11, 2013.

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  1. DuctDuck

    DuctDuck

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    0
    Jan 26, 2013
    I could really use a reasonable amount of help to evaluate my ground plane artwork. Proficient amatuers or professionals or funny looking guys with hair standing straight up!

    [​IMG]

    So far I have used metric measurements for the board outline because of my ABS box. Yet the traces, whitespace, and footprints are imperial. What I'm strugling with is parasitic capacitances. I have a copy of Terman's radio engineers handbook that I use for calculating resistances, capacitances, inductances for anything I make or have proximty to. A majority of the traces carry less than 9VDC

    trace width = 0.025 in (25 mils)
    trace spacing = 0.025 in (25 mils) but it could be more or less for some islands

    It's 1/2 a project to monitor my rj11 lines for faxes and a voice line. I demultiplex my phone to an available line if not engaged.
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    10,025
    2,138
    Nov 17, 2011
    Monitoring the fax or phone line involves frequencies where the stray capacitances of your PCB are of no concern. The capacitances of the telecom wires are much larger.

    Your artwork looks nice. One thing to consider: The three traces on the right, running from bottom to top, cut through the ground plane, effectively dividing it into 4 islands. This makes the use of a ground plane moot. You may consider placing wire jumpers in these places instead of the traces and close the ground plane instead.
     
  3. DuctDuck

    DuctDuck

    52
    0
    Jan 26, 2013
    Thank you for the input, HaraldKapp! Every little bit counts.

    If I may, the dividing vertical traces may isolate portions; I have tried to leave at least 25 mils at the very edges of the board. At the top most edge; the 18 egg pads, are three terminal bicolor leds and these connect to the ground plane with a smidge of 25 mils of copper left at the edge. You suggest more? Bring the leds down.
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    10,025
    2,138
    Nov 17, 2011
    That's sufficient if you look at the DC behavior only. But for AC, specially high frequency, things look different. AC current flowing in a big arc (as forced by the gap in the GND plane) sees a wire loop with comparatively high inductance. Also the wire loop acts as an antenna, emitting and picking up radiation.
    This may all be of no problem in the frequency range your circuit operates in.
     
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