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Old 24th January 2016, 10:20 PM   #1
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Default Trace path widths on PCB.

Hello, new to the forum so sorry if this is wrong thread.
looking for advice as to how wide a trace should be for HP/LP Filter designs on 1oz. PCB.
Using separate boards for HP/LP filters.
HP - 18Ga. Inductors and 250V Caps.
LP - 16Ga. Inductors and 400V Caps.

Currently the design has .125" traces.
I've looked at trace width calculators and don't know what I'm doing.
I based my design from the existing crossovers from the manufacturer.
Somehow I feel like I need to attend to this.

These Filters will feed Focal 8W woofer and ESS AMT5 Power ring in a bookshelf two-way.

Thanks.
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Old 24th January 2016, 11:02 PM   #2
rayma is offline rayma  United States
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Quote:
Originally Posted by Baronski of Boise View Post
looking for advice as to how wide a trace should be for HP/LP Filter designs on 1oz. PCB.
Can you post a schematic? You can use both sides of the pcb to double the copper thickness.
If the leads connecting to a node are soldered near each other, the width is less critical.

Last edited by rayma; 24th January 2016 at 11:23 PM.
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Old 24th January 2016, 11:10 PM   #3
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ax=copper ounces.
bx=current in amps

thickness in thou of inch = (1000 * (bx / ax)) / 66.6666;
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Old 25th January 2016, 01:56 AM   #4
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Quote:
Originally Posted by Baronski of Boise View Post
Hello, new to the forum so sorry if this is wrong thread.
looking for advice as to how wide a trace should be for HP/LP Filter designs on 1oz. PCB.
Using separate boards for HP/LP filters.
HP - 18Ga. Inductors and 250V Caps.
LP - 16Ga. Inductors and 400V Caps.

Currently the design has .125" traces.
I've looked at trace width calculators and don't know what I'm doing.
I based my design from the existing crossovers from the manufacturer.
Somehow I feel like I need to attend to this.

These Filters will feed Focal 8W woofer and ESS AMT5 Power ring in a bookshelf two-way.

Thanks.
Hi Baronski, generally as wide as you can make it. There is a trace width calculator built into this Android app.

BUT.... working with System7 (Steve) we've discovered some interesting interactions between the copper and inductors. There is measurable capacitive coupling and reduction of inductance when a large land appears under an inductor. It's rather surprising how thin it has to be to be measurable. I used to design my PCB's with giant copper areas. After this testing I've changed my mind.

Now I avoid copper lands under an inductor or large foil capacitor. This is counter to how a lot of commercial speaker PCB's are designed that try to use as much of the copper on the board as possible. It's not really needed. 1/4" traces will work for just about anything. I do think 0.125 is a wee bit thin, but probably not measurably worse.

If you want a more clear visualization, your trace calculators should provide you with mOhms of resistance. Plug them into something like XSim as resitors to examine the effects. XSim will also indirectly help you understand the currents flowing. Set the amplifier power to your maximum expected power and then look at the amperage per device. Then you can plug this current into the appropriate trace calculator. I'm pretty sure that if you do 0.250 traces you'll never notice it.
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Last edited by eriksquires; 25th January 2016 at 01:59 AM.
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Old 25th January 2016, 02:02 AM   #5
jcx is offline jcx  United States
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why PCB? - we are talking diy XO?

use perfbord if you like, hand wiring however should be a no-brainer
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Old 25th January 2016, 02:07 AM   #6
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Originally Posted by jcx View Post
why PCB? - we are talking diy XO?

use perfbord if you like, hand wiring however should be a no-brainer
JCX Is right actually. Also, tip from Sytem7, use wire tie anchors and hot glue to create mounting points for your expensive parts. This way you use wire ties for all the caps and coils, but hot glue never touches them. Makes it easier to remove them and re-use them later.

Best,


Erik
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Old 25th January 2016, 02:51 AM   #7
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Thanks for all the reply's. I am wanting to try to fabricate my own pcb. looks simple and thought it would be more professional. The original crossover had many variations in large lands, with 1/8" traces leading to ground and common circuits. I have room to widen the traces, but want to make sure it is necessary. I might revise my design with 1/4" traces as advised, then re-evaluate. Looks like I have to upload photos via url, so maybe later on the schematic.
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Old 25th January 2016, 03:08 AM   #8
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Quote:
Originally Posted by nigelwright7557 View Post
ax=copper ounces.
bx=current in amps

thickness in thou of inch = (1000 * (bx / ax)) / 66.6666;
It's the amps that are confusing to me. I plan to drive these with modest receiver. Power Amps and Receivers are not rated in Amps, so what am I missing?
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Old 25th January 2016, 03:31 AM   #9
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Quote:
Originally Posted by Baronski of Boise View Post
Thanks for all the reply's. I am wanting to try to fabricate my own pcb. looks simple and thought it would be more professional. The original crossover had many variations in large lands, with 1/8" traces leading to ground and common circuits. I have room to widen the traces, but want to make sure it is necessary. I might revise my design with 1/4" traces as advised, then re-evaluate. Looks like I have to upload photos via url, so maybe later on the schematic.
I like doing that myself. My one bit of advice though is you often end up tweaking a design for weeks after it's playing. Better to listen to it for a while before committing to a PCB.

Best,


Erik
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Old 25th January 2016, 03:33 AM   #10
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Quote:
Originally Posted by Baronski of Boise View Post
It's the amps that are confusing to me. I plan to drive these with modest receiver. Power Amps and Receivers are not rated in Amps, so what am I missing?
Use XSim. Simulate your crossover, you can even use an "ideal" speaker driver. Set the Amplifier to 150 Watts, and open up the AddGraph menu. Select More --> Component Current

That will give you a great idea of current vs. f for each component. Select components in series with your traces and you'll know exactly how much will flow in the trace. Since the current in the component must equal the current in the trace. A bit of a cheat, but a mathematically valid one.

Of course, you should also check the wattage of your resistors while using XSim. It's most accurate if you have a ZMA file, but you can at least get a rough indicator this way.

Best,


Erik
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