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which one is best?

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meowth08

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Hi,

A&E: poly gnd
B&F: poly vcc
C&G: polygon
D&H: no polygon

It's just a single circuit.
Software: Eagle
Isolation: 28 mils
Width of traces: 32 mils

I do not know how to define or describe "BEST".
Maybe you can help me choose critically.
I will make it as my own standard when making a board layout.

If you have better ideas, feel free to comment.

Regards,
m8
 

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  • pcb compare.png
    pcb compare.png
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Most of the time I would choose A, but it really depends on what the circuit does. For something larger it may be better to have more ground polygons that connect at single points.
 
Hi meowth08,

When I first saw your question, I was not sure what the question was. I may be wrong, but here goes.

It seems you are asking two general questions:

1) Should you have sharp right angles or use curves; and
2) Whether you should use a copper pour for GND, Vcc, or nothing (i.e., the pour is not connected to any signal???).

For the first question, you may find some help here on about page 11: https://www.electro-tech-online.com/custompdfs/2013/03/PCBDesignTutorialRevA.pdf

It is really just a matter of taste; although, that author (David Jones) suggests that sharp corners may lead to some manufacturing difficulties. Many people also prefer the look of 45° angles instead of 90°. From an electronic standpoint, no difference between rounded, square, or 45° angles can be demonstrated below about 1 GHz.

For the second question, I think you will find pours used more frequently than open boards with no pours. For one thing, it reduces the amount of copper waste. There are also electronic reasons to have signal pours for noise (e.g, a ground pour) or current carrying capacity. If weight were a big issue, you might opt to do without a pour.

Given that, and assuming weight is not a controlling factor, I would go with A-E or B-F. Of the two, I would go with the ground pour. In my mind, a short to a ground pour would be less likely to create a problem than one to a Vcc pour. On a power supply I built a few years ago, I had both ground and V+ pours.

John
 
On a power supply I built a few years ago, I had both ground and V+ pours.

Did you do it with eagle? I've never tried putting pours both on VCC and ground.
 
Yes, Eagle. You may need to change the "rank" of one or more polygons. You can have several polygons on the same board. The advantage of polygons over a geometric shape, is that polygons can be made signals/nets.

John
 
I tried using poly vcc and poly gnd at the same time. However, it resulted to shorted VCC and gnd on the circuit. Obviously, I'm doing something wrong. I changed the rank of vcc to 2,gnd stays at rank 1. F1 doesn't help. Could you please share the right way of doing it? :D

m8
 
Did you properly name each polygon?

Please post the files from what you are trying to do. Also, are you using Eagle ver. 6.x or something earlier?

John
 
Did you properly name each polygon?

Please post the files from what you are trying to do. Also, are you using Eagle ver. 6.x or something earlier?

John

Hi again.

I uploaded the files. I use version 6.1
Could you do it for me so I could see the result?
Thanks.
 

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  • audio preamp comm8.sch
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  • audio preamp comm8.brd
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I hope this works for you. VCC is rank = 1; GND is rank = 2

Not sure how you want things shaped, but this should give you an idea how to do it. Be sure to name them properly, e.g., VCC and GND.

I did not change the schematic, but uploaded it anyway so the link won't get severed accidentally here. Thermals are on.

John

BTW, I keep these thing in a test folder on my desktop, which is inherently crowded. So, I clear it after a few days. If I misunderstood what you wanted, please let me know in the next couple of days.

View attachment audio preamp comm8.brd
View attachment audio preamp comm8.sch
 
Hi John,

That's perfectly what I wanted to know.
I also figured out my mistake.
GND is rank 1 and VCC is rank 2.

BTW, sorry for late replies.
We just finished our examinations. :D

Thank you.
 
Hi John,

That's perfectly what I wanted to know.
I also figured out my mistake.
GND is rank 1 and VCC is rank 2.

BTW, sorry for late replies.
We just finished our examinations. :D

Thank you.

I think you want the ranks the other way around, so VCC excludes GND.

John
 
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