Autorouter?

zthee · Joined: Feb 20, 2008 Posts: 414 Location: Stockholm

As I've come to understand it it's bad to use the autorouter?

Since I'm a noob at laying out boards, using it seems like a pretty nice alternative. What's the problem?

Inventor · Posted: Sun Sep 06, 2009 3:22 am Post subject:

For low frequency audio stuff on small boards, I don't personally see much problem with a good autorouter like EAGLE CAD has. Autorouters have a bad rep because they were horrible for many years.

If you have any higher frequency (>100kHz) on your board, which I do on my latest project, you want to route by hand for those traces including good a ground plane and power routing. Placement is a big factor here, of course.

My plan is to autoroute and rip-up a few times until I get placement right, then hand route the high frequency stuff, then finally autoroute what doesn't matter much.

Oh, and autorouters tend to take shortcuts, making traces close to pads and whatnot. This matters more with poor technologies like home kitchen etching than with professional board houses.

Just my two cents, opinions vary.

Les

zthee · Joined: Feb 20, 2008 Posts: 414 Location: Stockholm

Thanks man!

That was my guess. But I wasn't sure... Smile

cloudscapes · Joined: Feb 09, 2004 Posts: 100 Location: Montreal

It's not just the high frequency stuff either. If you're mixing analog signals with digital (like clock pulses or control wires) or CV, it's something you want to keep in mind. You don't want CV/digital/noisy clock traces getting too close to analog, especially if you're building an effect. An autorouter might dumbly trace a crucial audio signal right under a noisy IC or something. Or might trace the ground all over the place where it would be preferable to star ground.

Inventor · Posted: Tue Jan 12, 2010 10:58 am Post subject:

cloudscapes is right on target. Gotta hand-route when it matters!

Les

zthee · Joined: Feb 20, 2008 Posts: 414 Location: Stockholm

I'm hand-routing everything! It feels safer, and it looks nicer Smile

Sure - it takes longer time. But when you're done, you know whats going on on the board!

Inventor · Posted: Tue Jan 12, 2010 2:49 pm Post subject:

true, true...

scriptstyle · Joined: Jan 22, 2008 Posts: 250 Location: nj

i few days ago i was in need of a lfo for a group of modules going behind one panel. i needed an lfo with a wide freq range, so i choose tims from magic smoke(8k LFO/TSW/TSQ)very cool LFO by the way thanks! i wanted to put the autorouter in eagle to the test. After a few hours of drawing up the schematic laying out parts auto routing moving stuff re routing, it did feel counter productive. there is just a lot of re routing to be done by hand anyways. A few hours later I had a etched board the next day i was testing. long story short it dose work for for simple op amp stuff. this technique did give me exactly what i was looking for at the time so no complaints.