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abishur
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Re: PCB woes!

Sat Oct 29, 2011 9:20 pm

So in another thread I was discussing the possibility of designing my own LVDS to DVI board off a schematic graciously provided to me by a member on another forum, when I hit a harsh truth: I know nothing about taking a circuit design and turning it into a PCB!

As you might imagine that's creating some... frustrations with me. I'm specifically attempting to make two separate boards:

1) A battery charger using the Maxim DS2715.

2) The DVI to LVDS board using the schematics here. Now as you can see in this one, they actually provided the board, but it's a PDF with glaring red background, not very handy for making a PCB.

Does anyone know some good resources for leaning how to convert a circuit diagram into a PCB program (and a good free PCB program? I was looking at eagle but it's not free)? Or if anyone already made a board for these chips and just want to send me the PCB file itself, I wouldn't mind that either.
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NoSuchNick
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Re: PCB woes!

Sat Oct 29, 2011 9:43 pm

I learned and use eagle, the Hobby version is free, but limits you to 2 layers and a maximum 8 * 10 cm board. The advantage of eagle is, that there is a lot of information and libraries out there. Many FAB service provide rule and export files, or accept eagle files directly. Disadvantages are that it is a bit harder to learn in the beginning and that Cadsoft has just been bought by farnell, and the future of it might be a bit wobbly.
Sparkfun has some nice tutorials for using eagle, and there are plenty of text and video tutorials floating around.

There are a couple others, like Designspark and various others, but i'm currently trying to learn KiCad. KiCad is free open source and has no limitations on sizes and layers, but is not as well polished as some of the other offerings. My reason for trying KiCad is that I want to start making 4 Layer Boards at home and Eagle doesn't support that in the free version.

NoSuchNick
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Re: PCB woes!

Sat Oct 29, 2011 9:50 pm

Forgot to say:
Most or all of the programs that are freely available are of course not comparable to those used in designing something like the r-pi. If you start worrying about difference in trace length, coupling of signals, etc Eagle is not going to help you much.

Bacan
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Re: PCB woes!

Sat Oct 29, 2011 10:17 pm

Just off the top of my memory.

Circuit Cellar; the mag and website. Is that available in the UK?

Maybe Radio Shack, Forest Mimm, Frys.com (Huge Geek US Store)

Being a Software & Firmware type, I bartered a deal with my hardware consultant friends for one off work. From what I understand, there are PCB houses that will do 4-6 boards for $60 USD with 4-5 day turnaround time. Or so I heard.

Bakul Shah
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Re: PCB woes!

Sat Oct 29, 2011 11:14 pm

Here's a good list of PCB houses on ladyada.net. Also covers PCB software on another page.

geeus
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Re: PCB woes!

Sat Oct 29, 2011 11:14 pm

On the whole subject of the charging board I with use a so16 to dip16 converter/ demo boards available on ebay for not alot of pennies. and make the desiging on a breadboard to what the datasheet shows with standard size components. make sure it works first.
Then transfer the components to vero/stripboard to make some thing more permanent. There are some stripboard design programs for free on the net. at least this gives you working a working board to get going with. ( work on the principle of Keep It Simple Stupid). and I have never had much luck with my own circuit board etching.

on the other board there are converters for that type of smd but it starts to go well out of my comfort zone. especially when it comes to preventing crosstalk.

hi hope this helps
regards Gee
Gee The Rabid Inventor :)

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abishur
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Re: PCB woes!

Sun Oct 30, 2011 4:23 am

Thanks for the tips, does anyone know a good resource for learning how to look at a circuit schematic and turn that into a PCB design?
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WizardOfOZ
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Re: PCB woes!

Sun Oct 30, 2011 6:17 am

Quote from abishur on October 30, 2011, 04:23
Thanks for the tips, does anyone know a good resource for learning how to look at a circuit schematic and turn that into a PCB design?
While I would love to be proven wrong, my suspicion is that you won't find any, assuming you are talking about *any* schematic in the general case.

In many cases you'd need a detailed understanding of the inner workings of a schematic, combined with the fundamentals of electronics, in order to successfully design a suitable PCB. While the details may not be critical in many cases, the trick is to recognize when they are, and that you may need to consider one or more of: Trace inductance, capacitance, resistance and coupling, heat dissipated (where, how, how much, how hot), enclosed loop areas, track currents, noise (coupling of same/prevention of/sensitivity to), grounding, on top of all the parameters I am probably forgetting right now.

Some schematics won't even have a direct and simple 'translation', because the PCB layout is the secret sauce in itself. The most infamous example is probably very high frequency radio equipment, like satellite receivers. Here circuit elements like coils, capacitors and filters are directly fabricated from the copper foil on the PCB through carefully designed artwork in the copper traces. Designing those types of PCBs is anything but a trivial, home exercise in many cases. Even if you had a detailed schematic with components values, it would get you absolutely nowhere. You'd need the means through some heavy computations to turn those numbers into actual PCB traces and artwork.

All of this boils down to why many hobby electronics enthusiasts tend to run into trouble sooner or later, once they go beyond the basics. Many simple and low speed/low power gadgets can easily be fabricated through various methods. Yet at some point *all* the simple fabrication methods and rules of thumb break down, and the constructor *has* to have at least some understanding of the fundamentals of electronics to succeed. Unless, that is, the constructor is satisfied with only copying designs from the hands of others.

Which is why giving one of those nylon breadboards to a buddying electronics enthusiasts is probably one of the most evil things you could do to him/her.

Sorry if this got a bit far afield. No easy translation from schematics to PCBs in many cases I'm afraid.

WizardOfOZ
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Re: PCB woes!

Sun Oct 30, 2011 6:45 am

PS: There appear to be a critical error in the schematic for the example switching regulator, figure 5, in the DS2715 datasheet. It won't work as presented if you made a PCB based on it.

Bacan
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Re: PCB woes!

Sun Oct 30, 2011 10:46 am

I'll see if I can find in my Pack Rat Pile of information the title of a book from about 12 years ago that goes into the Black Magic of Circuit board layout. There comes a point where the size and speed of circuits require you to start knowing a Lot about weird physics and using what is not logical. May take a few days before it is found.

Lakes
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Re: PCB woes!

Sun Oct 30, 2011 12:24 pm

PCB Design for Dummies? :)

Bacan
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Re: PCB woes!

Sun Oct 30, 2011 3:13 pm

Quote from Lakes on October 30, 2011, 12:24
PCB Design for Dummies? :)

Your close! Circuitbuilding Do-It-Yourself For Dummies

As promised, I checked in my pocket folder where titles of useful books are kept. No luck matching paper to what my mental vision of the book ad should look like. So next step; To The Web!

On Amazon searched using printed circuit design also printed circuit layout

Found a fair number of possible books. Spoiler Warning: These books are going to cost you, each is between $50 and $125 USD. So, budget $250 for books maybe. Personally, unless your going into the PCB design & layout field, bribe a friend with the skill, and use a PCB quick turn house. Just my opinion. I've also found that Amazon's suggestion listed below a book's detailed description can be Very useful in offering bread crumbs to a solution.

Best Wishes with your etching. I'm sticking to Software/Firmware and Business development.

clivef
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Re: PCB woes!

Sun Oct 30, 2011 4:04 pm

I did this a few years ago to make a dive computer interface and LCD driver. I knew nothing about electronics - and still know very little - yet I made my own boards from schematics, etched and built them. So I'd say have a bash, at worst you'll waste a few quid but learn lots of new, interesting stuff.

I found this guide pretty useful.

The main thing is to get some decent PCB design software and have a play . Drop the components onto the board and join them up. Yes folks, this is all it takes to be a PCB designer! Hurrah! ;)

Then get someone round here to check it :D . Then make your rats nest into a PCB design using the auto-routing in the PCB software. Again, the pros will now be weeping into their hands :) . But you are not a pro, autorouting is your friend . Drag components round and autoroute again. And again. (It is likely that you will need to route some bits by hand.) If your software doesn't have an autorouter built in e.g. freepcb.com then you can pass it to freerouting.net to route. Lastly etch it - but that's another story. Job done! (cough).

Lastly, be prepared for it to all go horribly wrong and to send it to a PCB house or get a mate to do it. (That board does look a pretty complex beginner project. :))

Bacan
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Re: PCB woes!

Sun Oct 30, 2011 4:18 pm

I agree with clivebeale; Go Do It.

In rereading the thread, I realize my mental model was more complex (4-6 layer PCB), than what you may need to do your project.

Please document your experience and share with others your learning process and results.

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abishur
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Re: PCB woes!

Sun Oct 30, 2011 4:39 pm

@wizard, my little boards shouldn't be that complicated, especially the battery charger. We should literally be talking about an input side for the power, an output side for the battery, and a second output to the r-pi itself. I'm planning on doing the regular linear mode charging as showing in Fig. 6 (I'm going with the K.I.S.S. method ;) )

Also, I talked to the guy who designed the LVDS circuit and he sent me the source files. I've uploaded them to a dropbox location, you can get the link to it over in the LVDS thread here

Thanks to everyone for resources (I'm a cheap-skate so I probably won't shell out 50 bucks for a book, but I am looking at the Make Discover book, it's more breadboard design, but you gotta start somewhere, right?)
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NoSuchNick
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Re: PCB woes!

Sun Oct 30, 2011 4:43 pm

Just one point:
If you want to do more than those 2 boards (i.e. make electronic circuits your hobby) or if you want to etch the boards at home:
Don't use the autorouter!

It is not that hard to route boards by hand - It can actually be a fun game.
But if you want to etch them at home, you will have to teach the autorouter lots of exceptions (no small / plated vias, some through hole components can only be soldered from one side, no vias below smd componentes, ...) and if you work more with circuits, you will soon run into limitiations of the autorouter. There are good ones out there that can help a lot, but those are usually not found on free or hobby level software.

clivef
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Re: PCB woes!

Sun Oct 30, 2011 6:19 pm

I understand why seasoned PCB makers say don't use the autorouter. Generally it's good advice. On the other hand, here's a board that an autorouter made for me in about 10 seconds:



It was a simple, one-shot thing and hand routing it would have been a waste of my time. I etched it at home using the most basic techniques (iron-on laserjet print + ferric chloride). It worked. I saved over £100. Yes, it was a simple one sided board, but horses for courses and all that.

Bakul Shah
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Re: PCB woes!

Sun Oct 30, 2011 9:36 pm

On the other hand, you can just *draw* a circuit with conductive ink! Just glue down components on a piece of paper and connect them! No need for vias. Just stick a piece of paper on existing `wire' and draw another on top! There is a video online that shows how to make your own conductive ink.

WizardOfOZ
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Re: PCB woes!

Mon Oct 31, 2011 11:52 pm

@abishur, Yup, the linear version of the battery charger doesn't look too difficult to implement, seems rather harmless.

However your other project idea may not be as simple as that. While the number of parts is quite low, the technical requirements may be harder to meet. When we start talking about up to 165 MHz clock frequencies, timings below 1 nanosecond, impedance requirements on connections and a maximum tolerable differential clock skew of 50 pico seconds (1E-12 second), then I wouldn't want to say it is simple just like that. You may be right and the layout you link may work great, but I wouldn't be able to say without spending some time looking over the details and datasheets with some care. This in addition to me just ignoring the parameters, which cannot readily be inspected by eye, like the characteristic impedance of a given trace on a PCB.

That project serves as a neat example of why PCB design may be problematic in some cases. One would have to understand all the technical jargon in the datasheets to be able to see if a given design meets all the requirements, and additionally make sure it follows the recommendations from the manufacturer for PCB layout with a particular part. An implementation may still work well, even if it doesn't meet all of them, yet you'd basically just be back to hoping that it works.

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abishur
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Re: PCB woes!

Tue Nov 01, 2011 2:16 am

Yep, that's why I'm glad someone already made the board for me and sent me the gerber files. I know that the board already works ;)
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brendi
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Re: PCB woes!

Fri Mar 21, 2014 10:09 am

i would read eagle´s tutorials, always find an answer there.
especially questions about circuit design into pcb

jamesh
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Re: PCB woes!

Fri Mar 21, 2014 10:48 am

brendi wrote:i would read eagle´s tutorials, always find an answer there.
especially questions about circuit design into pcb
Thread necro of the week! I think this may even be the best so far! No prizes I'm afraid, but thanks for the link.
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