Fundamentals friday: how to properly use autorouters

[ivan747]

I'm pretty sure there is interest in this. I have seen boards that make me go  even in some magazines, because the autorouter absolutely sucks. Look at this board:


http://www.webelectronica.com.ar/montajes1/nota15.htm
This is a real publication. This magazine is actually sold for money!

So if the autorouter disease is already spread, could you inform people how to really use this?
Cheers,
Ivan

P.S. oh and that board is for a 72MHz carrier frequency transmitter that is supposed to turn on a relay remotely. We all know they didn't even bother testing the circuit.

[Psi]

Fundamentals Friday: how to properly use autorouters....
.... don't

Really, they're only useful for niche application and take a long time to setup correctly.

[ivan747]

Fundamentals Friday: how to properly use autorouters....
.... don't

Really, they're only useful for niche application and take a long time to setup correctly.

I was thinking more or less the same about his PCB design for manufacture tutorial. Yeah, maybe not under fundamentals friday, but it would be an interesting video regardless.

[EEVblog]

Really, they're only useful for niche application and take a long time to setup correctly.

Yes, and I've mentioned this before. They have their place, and are indeed an essential tool in the industry, but they have to be used in skilled hands.
Not easy to do a video on it because all autorouters are different.

[free_electron]

The problem is that every tool is different. You can't do a generic video....
Ideally the router is driven fromt he schematic. Special markers are putin the she atic that tell the router what signals belong together , what layer they should be on , how wide, the distance, the max length and other restrictions.

That is what it boils down to. You need to fee restrictions to the router.
If you dont tell it anything it just draw random lines. You need to telltot what it can and cannot do.
Depending on the router there will be a list of criteria. The more i telligent the router the more restrictions you will be a ble to feed it.

But, keep in mind, teaching the router is a time consuming task and it requires a lot of experience in doing manual layout to properly sett he criteria.

Autorouters are not a shortcut nor a replacement for a skilled pcb layouter. They are an assistant and can be a time saver for a complex board.

[marshallh]

I see one place where autorouters are actually worth using - huge pcbs with lots of parts where you can throw as many layers as you need at the problem.

Niche test equipment, communications/network equipment, military apps, these are all low volume compared to consumer markets but still have tons of money thrown at them. Going from a painstakingly hand-routed 6layer board to an autorouted 20layer board will make basically no difference in this case.

Heres a board that you would probalby mostly auto-routed, money is no object, it needs to be done yesterday, and the job needs to get done.

[tszaboo]

I see one place where autorouters are actually worth using - huge pcbs with lots of parts where you can throw as many layers as you need at the problem.

Niche test equipment, communications/network equipment, military apps, these are all low volume compared to consumer markets but still have tons of money thrown at them. Going from a painstakingly hand-routed 6layer board to an autorouted 20layer board will make basically no difference in this case.

Communication means 100Mhz+ signals nowadays. I wouldn't let autorouter touch those. Also, your amazingly slowly loading picture has Weitek chips on it. It must be 1990 technologies. With proper ground plane, lots of layers, for that time, the autorouter was acceptable. Today, the same board is one FPGA, with some memory.

[Kjelt]

I see one place where autorouters are actually worth using: military apps

ok now i am really worried