Best way to trace existing PCB (not for piracy!)

[julianhigginson]

well that thread sure was exhausting....

[Doctorandus_P]

Another vote for KiCad.

Quite recently a new feature has been added to KiCad-nightly. You can now load an image in the PCB editor and use that as a template to guide footprint and track placement.

https://forum.kicad.info/t/post-v6-new-features-and-development-news/32633/58

Do note though that it's a new feature and that the nightly version is likely to have some bugs. PCB's made in the nightly versions can also not be opened in the stable KiCad version. It is however a policy of KiCad to release a mayor version once a year, and KiCad V7 is therefore expected late this year or early next year.

[JohanH]

I have recreated PCBs in KiCAD by importing the image as a background in KiCAD PCB tool, then drawing new traces according to the background. Of course, first a schematic should be created.

[PlainName]

PCB's made in the nightly versions can also not be opened in the stable KiCad version

Why is that?

[pcprogrammer]

Why not use EasyEDA https://easyeda.com/editor

No need to install software and it is possible to order from JLCPCB directly or create gerber files. It is not difficult to work with it. You can also print the design 1:1 on your printer (If you have one of course) and check if things fit behind the existing panel.

Dual layer is not very expensive and makes the layout job easy.

Way easier than at home messing with chemicals to make your own PCB.

[JohanH]

PCB's made in the nightly versions can also not be opened in the stable KiCad version

Why is that?

Importing projects made by newer versions of software into older software versions is much harder to do than the other way around and is many times impossible. In order to make it possible, you would have to patch the old version so that it is able to import new features etc.

[JohanH]

Why not use EasyEDA https://easyeda.com/editor

It's not bad advice, but consider what you need. Personally, I like to archive old projects and be able to open them again, import them to newer software versions and create a new revision if needed. Now with a cloud service, can you be sure that you can do this in the future?

With KiCAD, in ten years the software could change so much so that a new version can't open/import a really old project, but you should be able to fire up a virtual machine, install an old version and at least be able to open the project.

[mikeselectricstuff]

Yes, this is exactly what I'm asking: What is the best tool to use to trace over this? I have no desire to draw up the schematic as it's irrelevant to manufacture.

Unless you have zero interest in ever designing a PCB now or in the future, then you absolutely should draw the schematic first. Schematic->PCB layout->Gerber->Manufacturing is THE process for making PCBs, so a) it's the process the software is designed around, and b) doing the schematic means you CAN'T wire the PCB wrong. I cannot underscore enough how important (b) is! So if you have even the slightest interest in electronics, learn the process, you'll be doing yourself a favor.

Not necessarily. There is no right or wrong way in engineering, only more or less appropriate for a particular situation.
Doing the schematic first can impose unnecessary constraints as choices are nailed down too early in the process. In many cases there is a lot of scope to swap pins & devices ( MCU I/Os etc.) and the optimal arrangement can be far from obvious until you start looking at the physical layout.
I never start from a schematic, instead I create nets as I go along during placement, and to a lesser extent, routing - put some or all of the parts down, create nets for all the things that are fixed, then see what the best options are.
There is still a netlist, it's just created during the layout process. (I use PCAD2006, which allows nets to be created during layout - I don't know how common this is in other PCB software).

For a job like this, where you already have a layout, starting with a schematic would be a waste of time unless you intend to make substantial changes.
As mentioned above it's not worth the effort to convert from a scan, and much quicker to re-draw it from scratch in a PCB package.
 

[pcprogrammer]

Why not use EasyEDA https://easyeda.com/editor

It's not bad advice, but consider what you need. Personally, I like to archive old projects and be able to open them again, import them to newer software versions and create a new revision if needed. Now with a cloud service, can you be sure that you can do this in the future?

With KiCAD, in ten years the software could change so much so that a new version can't open/import a really old project, but you should be able to fire up a virtual machine, install an old version and at least be able to open the project.

There is an offline version of the software available, so store that package with your designs, which you can also archive locally, and you are good to go, as long as the hardware will support it. Because old software like for instance OrCAD needs either an emulator or old hardware to run. Might be a bad example when a new version of the suite is still available today and old designs can be loaded into it, but he.


About drawing a schematic first and then the PCB, I think that depends on what you are used to, but I see it as an iterative process. I mostly draw up a schematic first, then start to shuffle the components round on the PCB design and when needed I do pin or component swapping in the schematic and annotate the PCB until fully satisfied with the result.

[PlainName]

PCB's made in the nightly versions can also not be opened in the stable KiCad version

Why is that?

Importing projects made by newer versions of software into older software versions is much harder to do than the other way around and is many times impossible. In order to make it possible, you would have to patch the old version so that it is able to import new features etc.

Ah! Of course - the nightlys are going to be newer. Duh

Edit: to clarify I was thinking it meant if you used the nightlys then you couldn't open the files with the next full version (that is, the stable when it's caught up). But you can read it either way and obviously I saw the wrong one.

[tooki]

Why not use EasyEDA https://easyeda.com/editor

It's not bad advice, but consider what you need. Personally, I like to archive old projects and be able to open them again, import them to newer software versions and create a new revision if needed. Now with a cloud service, can you be sure that you can do this in the future?

With KiCAD, in ten years the software could change so much so that a new version can't open/import a really old project, but you should be able to fire up a virtual machine, install an old version and at least be able to open the project.

FYI, the way EasyEDA works right now is that it runs the version of the software the project was last saved in. If a new version is available, it asks whether you want to upgrade the project or not. So it seems that at least now, it actually has multiple software versions on the server to run as needed.

[daxliniere]

For a job like this, where you already have a layout, starting with a schematic would be a waste of time unless you intend to make substantial changes.

Finally! The voice of reason!

Yes, I am trying to create a 1:1 replica of the original membrane PCB, there is no need to interpret the wiring.

[ataradov]

Finally! The voice of reason!

Post #3:

You won't even need to make the schematic, you can just layout the board.

But given that replacements are readily available, they are probably the best way to go. Ordering the board that size would cost about the same anyway.

Milling or any other methods trade in quality and time. It all depends, may be worth trying. You will always have an option to buy the replacement panel.

[nctnico]

For a job like this, where you already have a layout, starting with a schematic would be a waste of time unless you intend to make substantial changes.

Finally! The voice of reason!

Yes, I am trying to create a 1:1 replica of the original membrane PCB, there is no need to interpret the wiring.

You may think that but the whole goal of a schematic is to be able to check whether everything is connected in a sensible way. The keypad will typically consist of a matrix but the PCB layout can severely obscure that. It would be a hard lesson when it turns out the wiring is wrong after spending a lot of money on having a PCB made.

And why aren't you ordering a replacement panel? I doubt going the DIY route will end up being cheaper.

[ataradov]

You will still have the layout file to check against if necessary. There is absolute no need for a schematic here. Plus you can make an error in recreating the schematic anyway. It is just a waste of time.

[tooki]

Yes, this is exactly what I'm asking: What is the best tool to use to trace over this? I have no desire to draw up the schematic as it's irrelevant to manufacture.

Unless you have zero interest in ever designing a PCB now or in the future, then you absolutely should draw the schematic first. Schematic->PCB layout->Gerber->Manufacturing is THE process for making PCBs, so a) it's the process the software is designed around, and b) doing the schematic means you CAN'T wire the PCB wrong. I cannot underscore enough how important (b) is! So if you have even the slightest interest in electronics, learn the process, you'll be doing yourself a favor.

Not necessarily. There is no right or wrong way in engineering, only more or less appropriate for a particular situation.
Doing the schematic first can impose unnecessary constraints as choices are nailed down too early in the process. In many cases there is a lot of scope to swap pins & devices ( MCU I/Os etc.) and the optimal arrangement can be far from obvious until you start looking at the physical layout.
I never start from a schematic, instead I create nets as I go along during placement, and to a lesser extent, routing - put some or all of the parts down, create nets for all the things that are fixed, then see what the best options are.
There is still a netlist, it's just created during the layout process. (I use PCAD2006, which allows nets to be created during layout - I don't know how common this is in other PCB software).

For a job like this, where you already have a layout, starting with a schematic would be a waste of time unless you intend to make substantial changes.
As mentioned above it's not worth the effort to convert from a scan, and much quicker to re-draw it from scratch in a PCB package.

My point is this: starting from a schematic is what most EDA software is designed around. Hence why I made my suggestion with the caveat of not bothering if PCB layout is something they never intend to do again.

As for pin swapping: Yep, that’s an important thing, which is why good software also helps you swap pins and components around in the layout and push the changes back to the schematic.

For a job like this, where you already have a layout, starting with a schematic would be a waste of time unless you intend to make substantial changes.

Finally! The voice of reason!

Yes, I am trying to create a 1:1 replica of the original membrane PCB, there is no need to interpret the wiring.

I wasn’t being unreasonable. You clearly didn’t bother seeing the point of my comment: IF you plan on doing electronics in the future and making more PCB layouts, then learning the standard way is a good learning experience. (And reverse engineering a schematic is a great way to have a schematic to practice layout with without having to design a circuit from scratch.)

If you don’t plan on ever laying out a PCB again, then skip it. Just know that the software may fight you every step of the way.

You may think that but the whole goal of a schematic is to be able to check whether everything is connected in a sensible way. The keypad will typically consist of a matrix but the PCB layout can severely obscure that. It would be a hard lesson when it turns out the wiring is wrong after spending a lot of money on having a PCB made.

Exactly.

You will still have the layout file to check against if necessary. There is absolute no need for a schematic here. Plus you can make an error in recreating the schematic anyway. It is just a waste of time.

For a one-off thing, yes. But if learning electronics is also a goal, then it could be time well spent.

[PlainName]

Plus you can make an error in recreating the schematic anyway.

Indeed, but the point of the schematic is that it's easier to read than a layout, so mistakes should be more obvious. Further, you can decide your layout is not going to make it for some reason and do it completely differently, but the schematic will ensure that it's still electrically correct.

[ataradov]

This topic is about recreating an existing layout, and a very simple one at that. What is not going to make it here?

If there were no readily available version, if I were to recreate this, I would also add through holes from the buttons to the pads on the other side. Even if I completely mess up the layout, it would not matter. I can always wire the boards however I want.

This is not some mass production situation, you are just making one. Stop overthinking it and just make it and be done with it.

[daxliniere]

Progress.
(Laminated MDF test plate)

[fourfathom]

Are there actual traces in those interdigitated fingers?  It looks like some of them are completely milled away.  And your un-milled groundplane will also be connected when the conductive switches are depressed -- will that affect the switch decoding?

[Warpspeed]

Its obviously a keyboard layout.
Those interdigital fingers get shorted together when a button is pressed.
Pretty simple, no electronis, just dumb wires and connectors.

Its probably the only example I can think of, where a circuit diagram is not going to be at all useful.

[daxliniere]

Are there actual traces in those interdigitated fingers?  It looks like some of them are completely milled away.

Yes, you're correct, they were eroded away. This was just a test as this would be the finest thing I've done on my CNC mill. Now that I've seen it works, I just need to adjust the radial offset to account for the V-shaped cutting bit. Also, this is a piece of MDF laminate flooring, so not nearly as rigid as copper-coated FR4.

And your un-milled groundplane will also be connected when the conductive switches are depressed -- will that affect the switch decoding?

Ahh yes, that's an excellent point. I'll add some cutaway rings around the interdigitated* fingers to avoid shorts. (*by the way, I LOVE that word.) Cheers, fourfathom.

[fourfathom]

Yeah, I've done a bit of PCB milling on my Shapeoko.  Keeping the PCB flat is critical, as it doesn't take much variation in V-bit depth to go from "just a scratch on the copper" to "no trace left" (especially with narrow traces).

[daxliniere]

Hmm.. seems like 0.8mm endmill might be the better option, then. I have a 0.5mm, but I've been too afraid to use it - it looks like it'll snap if I look at it the wrong way! 

[PlainName]

Hmm.. seems like 0.8mm endmill might be the better option, then. I have a 0.5mm, but I've been too afraid to use it - it looks like it'll snap if I look at it the wrong way! 

For a PCB the way to go is with a V-cutter and a big angle - 90 degrees is good! Obviously, whilst the tip is much less fragile, the depth of cut is really important so your PCB must be flat and square. I use carpet tape to stick the PCB onto the mill's bed, which ensures it's flat and only varies by the PCB thickness tolerance.

Also, 3-in-1 or other cutting oil spread over the surface both keeps the bit from going blunt and stops the PCB dust from going everywhere.

Apols if you already do or knew that. Originally I tried small bits, shallow V-cutters, etc., so ISTM you may be at in the first leg of your PCB making journey.