Electronics > Beginners
Breadboard layout vs PCB layout
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lordvader88:
How often do u lay out a PCB just like on the BB ? Some PCBs are nothing like how a BB version would look. Today I'm making something and I should just copy the BB version almost exactly,, it's a linear DC PSU with only BJTs being active. It looks perfectly logical, neat and tidy, and fills the BB more or less.

But I'm wondering how a professional, or a CAD program would lay it out. For such low frequency, maybe the whole would be all jammed together in a big maze/knot

Whats a good free program that takes a schematic and makes a circuit layout ? I'm using perf.board with the single copper rings. For that matter can LTspice make a layout ?

When does it matter the angle of traces/wires, when changing direction ? Lot's of old AM/FM radio's sure didn't care about curved traces, and a big maze/jumble of parts. Are 90deg angles always preferred ? Is that due to the magnetic fields of currents ?
Siwastaja:
Such auto layout tool hasn't been made and probably won't be in the near future. The problem is way too complex.

Some dedicated layout generators do exist, for example the TI Webench which basically crunches and modifies TI's pre-built power converter layouts to suit the user parameters. IMHO, they are of little value.

What comes to your question, depends on circuit. Sometimes it just happens that a certain circuit schematic works very well on a breadboard, and if this is the case, the optimal PCB layout would look similar.

But, a PCB design gives you so much more freedom, especially if you can afford extra layers. Given a fixed circuit complexity, the more you have layers to work with, the easier everything gets.

Trace angles are electrically irrelevant unless we are talking about really high-speed radio frequency stuff.

On the other hand, good reference planes (contiguous ground pours, preferably at least one layer dedicated to ground only) tend to be very important in many different types of circuits (almost anything but the simplest very low-frequency stuff): power converters, seemingly low frequency stuff that still have high edge rates (think about a 8MHz microcontroller), sensitive analog stuff, high-speed digital circuits, or, of course, RF.

But a circuit consisting of a connector, series resistor, and an LED wouldn't care about a ground plane.
Kleinstein:
With a good voltage regulator one may still have to watch out for trace resistance. Ideally one would also do this on the breadboard, but there one tends to accept a few more compromises - though contacts and resistance are often much worse.

Even for a DC supply the regulation loop may still have a loop gain up to the low MHz range. So at some points one may have to keep an eye on the layout. Especially the low output impedance part is sensitive to parasitic inductance.

Its rare the the PCB layout will directly follow the bread board. Usually one can do better with part placement.

The quality of the auto-router is often still quite marginal, especially with only 1 or 2 layer analog circuits. Very good ones may be wort it ar 4 layers or so for some part.  Automatic placement tends to be even worse - though with some KI this could work in the future. At least I have not seen anything useful.
cur8xgo:
Auto-routers can be very powerful tools if setup right. They certainly do exist and are used all the time. They can make sure vast amounts of complex rules are followed and are much cheaper and possibly more reliable (rules wise) than having a person lay out something like a motherboard or some other super complex multilayer PCB.

That said, not justified for simple circuits, and you would spend as much time configuring the auto router as you would just doing the layout yourself. Making a layout is a good skillset to build and will pay off in big ways.

I have used auto-routers to router very dense, very small, but not that complex PCB's before. Did a great job.

lordvader88:
I'm making a linear DC adjustable PSU, and the main guts, minus the knobs, will easily fit on a 9x15cm perf.board. And I could have nice straight rails. It uses 3 transformer winding.

I also have 9x15cm copper clad board. That would be fun, would there be any real difference to deadbug the thing ? I know for RF yes, but since cost and time don't matter, would it make it an "expensive" and better linear DC adjustable all BJT PSU, if I used copper clad, would it really make it even quieter ? I plan on putting it in a DVD player case.

I find on perf.board, it's too easy to pile on the solder. I need to use the trimmed leads as wires/traces way more often and make it much cleaner, and lighter too
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