[sdiy] Free CAD (was: Proteus software)

[Tom Wiltshire]

These don't seem like valid reasons to do a PCB layout without a schematic. Valid reasons not to work with crappy software, definitely.

In any half-way decent software, you ought to be able to change the package or footprint for a device without having to completely redraw the schematic. I've done this in DipTrace for exactly the reason you propose - through-hole and SMD versions of the same board. You can either change the footprint for the given component (can be dangerous if the SMD version of a device doesn't use the same pinout) or you can replace an entire device with the SMD version (safer and just as easy).

The other two reasons you mention are similarly down to flawed software. A good PCB/schematic package ought to be able to handle adding more components to the schematic after you've done a board layout. Again, I've tried this with DipTrace without any problems. It simply unroutes any affected parts of the circuit (often fairly little if you're *adding* - more if you're *modifying*) and leaves the PCB for you to finish off.

The final problem is similar - DipTrace offers the choice of "removing" a track or "unrouting" it from a PCB. Don't hit "remove" if what you meant is "unroute", but once I mastered that, I was fine!

Regards,
Tom


On 21 Feb 2011, at 18:03, Jay Schwichtenberg wrote:

> Several things come to mind for me at a hobbist level.
> 
> You may want to do two versions of the board. One SMD and the other thru
> hole. So you have to have two copies of the schematics one with SMD
> attribures for the components and one with thru hole. So now you have two
> copies of the schematic to maintain. They can get out of phase and cause all
> sorts of problems if you aren't careful.
> 
> Another thing is you do the schematic, make a board and go oops need to add
> a few more components. So you put some new components into the schematic and
> then go to the board. Some packages I've used have really barfed on that. In
> some cases they just couldn't handle it and in others they screwed stuff up
> so bad that you had to do the boards over anyway. Things might be better
> with the software that's out there today, don't know.
> 
> One thing I remember with a package I can't remember is that when you put a
> trace down that became the 'rubber band link' or node link. When you deleted
> that trace there was no 'rubber band link' or node connections and you had
> to put the nodes back in when you redid the trace.
> 
> Jay S.
> 
> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl
> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Ingo Debus
> Sent: Monday, February 21, 2011 8:11 AM
> To: Synth-DIY DIY
> Subject: Re: [sdiy] Free CAD (was: Proteus software)
> 
> 
> Am 21.02.2011 um 00:00 schrieb Ian Fritz:
> 
>> FreePCB allows you to do board layouts from scratch without  
>> schematics.
> 
> You can do this with Eagle too. You can even buy a layout-only  
> version, without schematic entry.
> 
> But what's wrong with drawing up a schematic first?
> 
> Ingo
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