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Old 25th June 2013, 03:45 PM   #1
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Default ESL with drilled PCB board

Hello all,

I have 4 the same machine drilled pcb clad boards.
The boards are 160mm x 290 mm
Bot sides have copper.
Openess ia around 50 %.
Drill size 4mm.

I have a few questions i cant figure out
- should i remove the copper from 1 side
- what is the best way to isolate the copper
- Can i still segment

I appreciate suggestions.


grtz

Simon
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Old 25th June 2013, 04:47 PM   #2
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Hi Simon,

The size you have is probably a good size to make a pair of desktop ESL.

I think that it's better that you etch out the copper on one side of the board. When doing that, you might also want to etch out the unneeded copper on the 4 edges of your stators too. If you want to do segmentation, you can do it too. But since your active diaphragm will be quite narrow, I'm not sure if segmentation can do any good.

Wachara C.
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Old 25th June 2013, 09:51 PM   #3
Calvin is offline Calvin  Germany
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Hi,

I'm not convinced about if it'd be better to etch off one surface side completely.
One could think of connecting this 'outside' surface to PE for safety reasons.
Need to think about the capacitance the safety surface forms with the hot surface though.
In any case needs the hot surface some etching. Every hole as well as the outer rim of the PCB should have a small etched rim, free of copper. Also, like Wachara already told, round off the edges and spare out where You gonna place screws, bolts or rivets to fasten the stators. Also You may cut away an edge or a small slot to create points where wire can contact the copper and the diaphragm contact.

For insulation there are special isoltion laquers used in PCB manufacturing and processing, that exhibit high cohesion. Those will tend to form nicely rounded edges, so that the holes remain open and don't fill with laquer or get even closed.

jauu
Calvin
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Old 26th June 2013, 05:45 AM   #4
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Thanks for the comments.

Would this size be sufficient for a mid/tweeter ?
I have ran a quick sim on

Electrostatic Loudspeaker (ESL) Simulator

And it suggest that it could.

grtz


Simon
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Old 26th June 2013, 06:09 AM   #5
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Yes, it will make a Great mid/tweeter!!!

jer
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Old 26th June 2013, 01:17 PM   #6
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I think that with a panel that wide you should consider either electrically segmenting it. Or mechanically segmenting it with 2 or 3 sections.

I get about 20 to 30 degrees of horizontal dispersion with my panel that has a 3.25' wide diaphragm.

Also what are you planning on insulating the stator with?

I have found it takes about 8mil of insulation thickness using some common off of the shelf Clear Spray Acrylic Enamel in order keep them from arcing at high levels.
The paint is good for as much as 1500v per mil and maybe as high as 2100v per mil in some cases.

As mentioned earlier minimizing any and all of the sharp edges of the Clad is a must!!!
Especially at each and every hole.

This can be simply done by chamfering the holes lightly with a larger drill bit and then give it a short bath in some etchant.
The will also help round off and dull the sharp edges leftover from the machining.

Or else they can start to breakdown and arc and once this happens it is extremely difficult to repair and sometimes impossible.

I know this from past experience and the time I spent trying to repair one of my panels I could have built five more and it ultimately ended up in a charred useless panel that is now beyond repair.

FWIW

jer
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Old 22nd July 2013, 10:33 PM   #7
WrineX is offline WrineX  Netherlands
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here a small panel i was working on, not yet cnc cutted.

the lines around the circles is coper clad, the green small circle is the actual hole, the bigger green circle is the where the copper is gone , but left the pcb, either by etching or with the same cutter that makes the holes on a cnc machine.

you can see that where the spacers are, it does not contain any copper clad anymore. this reduces ur capacity and change of leakage or arcing.
I added 2 points on the copper clad to solder the cables to the next panel. also there are two little pieces left of copper clad where the copper tape is soldered for the high voltage, you can link this spot to the next panel.


ofcourse you can also use pockets instead of holes, like sanders does. this is nice if you have a cnc this means less drilling more cutting , its faster.

ofcourse you slice the copper clad with and isolated path to segmend the stator. But first think of a sigmentation because you cant alter it when its done, or you have to use the dremel

i might even try powder coat the remaining copper clad. because it has to be conductive it will end up only on the copper. this way you can get a verry thick coating, wich is only on the outside of the panel. the pcb itself can handle allot of voltage before it arcs so the inside dont need any insulation. (as long as you ahve copper to the outside ofcourse)

keep in mind to use thin pcb single sided copper clad. 0.5 - 1 mm for instance. i know its wobly, but you can reinforce it like quad did with a plastic louvre or any other form of bracing. point is the thicker ur PCB the further away ur copper is from the membrane.


a blue line i see ur dutch, ill send you my Phone number in case you have questions. maybe we can help eachother out.
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Last edited by WrineX; 22nd July 2013 at 10:46 PM.
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Old 3rd December 2013, 04:36 AM   #8
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WrineX, did you ever make this stator?
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Old 4th December 2013, 09:48 PM   #9
WrineX is offline WrineX  Netherlands
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nope, i wondered of to wires. and now i wished i just bought some PCB would have been done 4 times by now. and saved me over 200 euro of glue's louve's wires Jig's etc and had a nice powder gun included

i will make one in the future, and i wil post it ill keep you updated. but i start it only when i got a tribo powder coat gun. because aplying 5 layers of paint is no fun


there is also one minor thing i ahve to find a solution for, that is some sort of spring loaded cutter or floating spindle head for my cnc, because the table is never 100% flat, cutting only the copper clad will need a verry flat surface. or a floating head that floats on the the PCB material so it remains a fixed distance to the cutted material so wehn i say cut 0.1 mm deep it actually cuts 0.1 mm instead of 0.1 + the ofset of the not flat table.

i did find a nice program to let my cnc probe the woble or the not flat surface by testing the distance to the material in a grid. after probbing i can use these data to let the machien compensate for it. did not try it yet but it worked for others.

Last edited by WrineX; 4th December 2013 at 09:57 PM.
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