PCB Layout Designers

I personally always start with the schematic and then move to the PCB just because the PCB tool verifies that I did not leave any connection unrouted. And with more than 20 nets, this becomes increasingly interesting to have.

Tom wrote: I am still using an old DOS version of EasyPC Pro for PCB layout,

I don't think £447 is excessive for the features you get with the complete unlimited version. And by the sound of it, your PCBs could almost certainly get away with one of the limited versions.

You can enter directly to the PCB with EasyPC (always have been able to as far as I know), and add the nets manually. Recent versions will produce a ratnested schematic from the laid out PCB.

For anything except trivial PCBs (a resistor and a LED say), it's always more secure to start with the schematic. It's much easier to verify. But also remember to verify the PCB packages. Never trust your own library, let alone someone else's.

Paul Burke

Protel AutoTrax will do exactly what you want, it's now freeware.

A lot of people (Hobbyists and one-man-bands mostly) still do the PCB only from a handdrawn schematic, but almost no one does that in professional circles.

AutoTrax will even let you generate a netlist from your hand drawn PCB, and then you can still do some basic DRC checking.

Dave.

Sure, EAGLE from CadSoft. It comes in three modules -- schematic, board editor, and autorouter -- that you can buy seperately. So if you only buy the board editor you get exactly the functionality you want.

Everybody (except your dad) does it in CAD, from schematic upwards. It's sooo much easier to maintain consistency between schematic and board. Of course many people first draw schematics by hand, but before they go to the board stage they'll recreate the schematic in CAD and then do the board in CAD as well.

Remember: If the CAD schematic is correct, there is NO WAY the corresponding board could be electrically faulty (i.e., have missing or wrong connections between parts) because the CAD package will always ensure 100% consistency. Or is anybody aware of a CAD system that doesn't maintain board-schematic consistency? That would be something to steer clear of.

robert

Well most programs have the odd bug now and again. But it does reduce the incidence.

gEDA's PCB was originally designed to work standalone, and it still retains that capability. You can pull component footprints from the parts library, connect up pins to form a ratlist, then route it. It can even use a scan of a pre-existing board as the background, to act as a template for replicating lost designs.

ExpressPCB software allows both approaches; the PCB side does not require the schematic, and if you *do* use it, the result is a bit clunky - slightly better than a kick in the head (unless there most recent update improved matters). BUT, the result is that you have them do the boards, typically in pairs (2, 4, 6, etc). If you want gerbers from their software, forget it.

I have made pc boards since the early 1970s and always have done them "by hand" (first black tape, then blue/red/black, and now via software).

Is it still the case that gEDA will not work in WinDoze?

AutoCAD ? A few footprints and you're there.

Rene

It's correct, almost by definition, but there are ways a schematic can

*look* correct, and not be. That's why (in addition to running DRC, of course) I always create a human-readable netlist and give it a decent lookover (thanks to, IIRC, John L for this suggestion).

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

gEDA has worked in Windows for a while now.

We just don't have a pre-built binary for it. But then again, we don't have pre-built binaries for Linux either. So, you have to figure out how to build and install it yourself. PCB at least comes with suitable scripts and readme's for building under Windows.

Sorry, I was not very clear there, yes EasyPC does indeed allow this and always has, and although =A3447 is not that much, for a one man band that only uses it occasionally if there were a cheaper or freeware version around that oly provided the libraries/gerber/drill and PCB design function that would be preferable.

The designs in question are considerably more complicated than a resistor and LED ;-) However a lot of complexity is removed by the user of PIC's, and all of them have been made in production releases on vero-board before the PCB exists, so the design is is well known by my father.

The final fly in the ointment is that my father is not a computer competent person.

Tom

Maybe for you, but nothing ever works for me the first, second or third time. And in this case, one would have to somehow get the compilers (wil be more than one with my luck). Worse, the smallest download will be over 4megs, making it impossible (i am on dial-up). So, for gEDA, i would need a pre-built binary on CD.

Net result? gEDA will not work for me.

freeware.http://www.altium.com/Community/Support/Downloads/

Yep, the old boy is exactly that, the one man band!

I was really looking for something was Windows and current rather than DOS. Easy PC does the job, but the version we have is an old DOS program and the libraries are rather old now.

Tom

Hmm, this one really raised my hopes, what I failed to indicate was a Windows requirement.

Tom

I've seen Orcad Layout v10.x, on multiple occasions, mung up the net list mid way thru the project. It would tie separate nets together. At the end of the project, I reimport the netlist just in case Layout did something evil.

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Mark

What kind of errors are you looking for? It sounds like a lot of work, and it won't catch mistakes such as typos on part values.

Maybe it would be better to fix the conditions that lead to the errors in the first place.

For example, .1uf is sometimes hard to read when the decimal is obscured, so people usually put a zero in front to clarify: 0.1uf. Others may use "R" in place of the decimal, such as 1R5 for a 1.5k resistor.

I'm sure there are many other ways of doing schematics that help avoid mistakes, and developing these good habits can save a lot of time and grief. If you can only find 90% of the mistakes, it pays to reduce the number in the first place.

I tend to pick up most things in pcb layout and routing, so for me, a cad package that does back annotation is essential. I found trying to do it manually is very error-prone:)

Regards,

Mike Monett

Mostly stuff like hidden connections to supplies that have a variety of different names. For example, Vss, GND, Vee, etc. which can form an isolated net if there are multiple parts that use the same name, but you forget to check the names on every part with hidden power pins and make sure it's tied to the proper supply. That would normally get caught at layout, but it's better to catch it earlier. Similarly, typos on labels could lead to isolated nets with more than one node, so that DRC isn't likely going to catch it.

I prefer to show all the power pins on parts, but sometimes that makes the schematic too messy, and that could obscure other problems.

A number of years ago I was converting a schematic from hand-drawn to electronic and was a bit surprised to notice an obvious error. I'd fixed it without even noticing in the (manual) layout. Unfortunately, computers don't "know what you meant" to draw.

Best regards, Spehro Pefhany

--
"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Like you, I prefer to show all the nets on the schematic so they light up when you select them. Hidden nets are a recipe for disaster.

I usually end up writing a separate program to assist in naming nets, entering proper component values, generating the pin connections on new packages, and anything else that is tedious and error-prone. Most cad packages have macro capability which makes it easy to enter the data, or you can simply paste it into a data entry box.

Anything that reduces the chance for human error is worth considering, no matter how small or trivial it may seem.

A mistake takes only a second. Finding it can take weeks:)

[...]

I think the schematic should show everything - unused pins, unused sections of ics, power supply filtering, all bypass caps (naturally), and anything else that helps understand each connection on the board. I usually add separate pages at the end to show all this stuff.

[...]

Soon, maybe. As mentioned above, I try to add as much as possible in a separate data entry program and get it to check the info before putting it into the schematic. That saves a lot of time and greatly reduces the number of errors.

Regards,

Mike Monett