Hacker News Reader

Comment by fho | Hacker News Reader

Also: the Autorouter in Kicad is actually pretty useful ... if you use it as a tool, not as a magic problem solving machine.

I normally place components somewhat randomly, big chip in the middle, connectors at the side, small stuff close to where it belongs ... then hit the autorouter, look at the result and move around some components, hit the autorouter again, rinse repeat ...

In the end I'll end up with fairly good looking PCBs (e.g. https://imgur.com/a/rUGtBNa) without having placed a single line myself.

View on HN

Yep, autorouter makes easy work out of hard stuff. Folks who tell you not to use it haven't spent much time using one or are working at a very different level of polish. It's super convenient to draw some important power traces and let the router do its best with signals. If it's taking too long, you start rearranging.

> the Autorouter in Kicad is actually pretty useful...

For most toy projects it’s perfectly sufficient, but once you get into complicated stuff it will bite you back.

Using an auto router is like building your software by copy pasting from stack overflow indiscriminately.

I didn’t get the sense the autorouter was used anywhere near as often as that.

I don't think it is ... and I think some it is some sort of "get of my lawn"-ism. I passed a degree in electrical engineering at some point (haven't used it too much after that), and "don't use the auto-router" is basically what is taught from day zero.

So ... while I can't say anything about PCB design in industry ... I can say that I tend to use a auto-router for my small DIY audio projects and it has never really failed me.

And ... if auto-routers are not used in the industry ... maybe that is something somebody on here should "disrupt" ... computers have become just too powerful not to be combative in solving some constraint path finding problems.

I tried using the auto-router in KiCAD on my last <simple hobbyist> design and realized that it had been removed from KiCAD.

There was some external package that could do it, but at that point “screw it, I can route this board faster than reading the docs on how to deal with the autorouter” took over, especially since I couldn’t be sure anything I learned for this project would still apply for my next project if KiCAD later re-added an autorouter.

An autorouter is perfectly fine for whole classes of electronics. As a basic rule, if you'd happily assemble the circuit on a breadboard or with jumper cables and not worry about signal continuity, the autorouter will be fine.

It's only when you get to higher speed or higher currents that an autorouter won't have the context needed to effectively route the circuit.

But that's strange, isn't it? Higher currents basically just require wider traces, higher frequencies require very specific trace lengths.

That's nothing that can't be incorporated into an auto router.

Yea - I wish I had the time to write one which understands differential impedence, matched lengths etc.

Perhaps one exists, I don't know as I try to only use open source.

I am pretty sure that I saw some ads for a commercial PCB cad program that showed functionality for exactly that.

But yes ... probably not open source.

I think I should have added the caveat "with the typical information we give it".

I suspect that if we made enough effort at the schematic stage to properly annotate all the nets and define the types of signals flowing around the board, an autorouter could do a superior job to a human (from an RF emissions and trace current sense).

I've never seen a schematic with that level of annotation though. So as long as the person doing the layout has to use external knowledge of what they're laying out, autorouters will struggle.

In theory you could make EDA software which incorporated a full circuit simulation which was then fed into the autorouter to provide a layout optimised for low-EMI and high efficiency. That would be nice!

i use the Eagle one at the end of my routing flow:

first drop VCC and GND vias if you're using power planes, then route chunky power traces, route high-speed / differential pairs, finally autoroute everything else

on some boards, only 3-4 signals aren't power or something tight, but for LED Matrix boards with thousands of criss-crossing low-speed signals and other 'fun' projects with hundred of components (keyboards!), the autorouter is really the only way to go if you want to be done in a night or two

I loved Eagle until Autodesk bought them and turned that product into a subscription. Now, I’m locked out of my old designs. Fool me once, you’ll never get my money again.

Sad but true ... Last time I checked they still had the old standalone hidden on their web pages somewhere ... might be enough to open and convert your projects.

Kicad has an autorouter? Are you talking about FreeRouting?

Yep ... It's not exactly integrated, but usable.

I feel like somebody could have a academic career based around that

Reply on news.ycombinator.com