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scott2734
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Username: scott2734

Post Number: 185
Registered: 10-2005

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Posted on Sunday, 06 May, 2007 - 07:57 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

I have been working on a board for a few days and just cannot get it to trace right. I sarted the schematic editor and linked the pcb editor together so they would work together and cut some overhead.Im finding that this might be the wrong way to go, but cant understand why so many other people use the program this same way without any problems.

I have about 31 components on the schematic and board and the traces i put into the schematic WILL NOT do the same on the board.Say for instance, i have a pic 16F628A with a crystal and 2 22pf capacitors. I route the traces from the capacitors, straight throught the crystal to the 2 pic clock pins.In the schematic it looks fine, but when i look on the board the traces are going around the world to get to where i actualy put them. Do i need to manualy route these? If thats the case, the schematic editor is completly useless ! I counted, and out of the 31 parts on board so far, there are 5 traces going where i didnt put them?

How many people actualy use the schematic editor? Do some of you just start the pcb maker and manualy route the traces yourself? I was going to buy the full version, but i dont know if that will fix my problems. The auto route is useless too. I made the mistake of hitting that button and the thing went wild !

I am trying to figure out how to capture the 2 images to post on here to show what im talking about, but gotta figure out how to do that.
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mikehibbett
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Username: mikehibbett

Post Number: 659
Registered: 04-2005

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Posted on Sunday, 06 May, 2007 - 08:28 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

>Do i need to manualy route these?

Yes. Auto-routing will never have the level of intelligence that you have, so you have to take it's advice with a pinch of salt.

This is what I do:

When the schematic is complete, place the components on the board, and do an auto route. Make a note of the # of vias / % complete, then rip up the tracks, move the components around again and have another go. See if the % vias has gone done, or the % complete up. I find this helps me work out sensible component placement ( although don't forget to follow the usual rules about component placement for decoupling etc ).

When I am happy with the placement I then manually route the important signals - such as power, crystal, decoupling etc. Save that, and then experiment with autorouting.

I tend to use auto-routing for advice and suggestions rather than letting it loose on my real layout. I did that once; the resulting board would crash if you gave it a stern look. I'll never do it again!

Mike.
-----
www.drivesentinel.co.uk - Home build GPS Speed Camera Detectors
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magnum4
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Username: magnum4

Post Number: 470
Registered: 04-2005


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Posted on Sunday, 06 May, 2007 - 11:41 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

One thing Scott, The schematic does not dictate where the traces go.:-(

The way I use it is to turn off all layers except the bottom one, The make the size as large as I can And the clearence also, Run the auto router and look at what it produces.

I then move components around to get the best rout, sometimes manually routing some tracks, like power and crystal lines.
A lot of the time I only have to rotate a component or 3 to get it right. Also simply moving a component a few mills one way or the other can sort it.

I quite enjoy getting the best layout I can.

If you like send me the schematic and Ill try it out.

HTH.

(Message edited by magnum4 on 06 May, 2007)
Regards,
Jim
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scott2734
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Username: scott2734

Post Number: 186
Registered: 10-2005

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Posted on Monday, 07 May, 2007 - 03:43 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Ok , i think i fixed some of it. I had to put juntion dots at every point where the two capacitors met with the crystal. How come the rest of the board didnt have to have the juntion dots when i put a component in? It automaticaly joined the component with the rest of the board. Do i need to put juntion dots at every component when i put it in a trace? I hate doing something 50/50, if i need dots ill put them everywhere, if not, i need to figure out why it did that.

Thanks for the replies Mike and Jim, every little bit helps with me , considering im blonde lol. Jim, im going to try to figure this out without sending, at least until i start pulling out what little bit of hair i got.
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magnum4
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Username: magnum4

Post Number: 473
Registered: 04-2005


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Posted on Monday, 07 May, 2007 - 09:17 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Ok Scott, The components were not connected.

In eagle I find that you have to be very accurate sometimes with connecting wires, it looks as if the wire is connected but actually it is not.
The thing here is to catch the component and move it a little, the wires should follow it , if they dont then its not connected. sounds more difficult than it actually is.:-))
Re the dots, If you dont use them and run a drc , you will be informed there is missing junctions at such and such a position, so I always use them, but it will rout ok without those pesky junction dots :-))
HTH
Regards,
Jim
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scott2734
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Username: scott2734

Post Number: 189
Registered: 10-2005

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Posted on Tuesday, 08 May, 2007 - 03:46 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Somebody posted a trace chart on here a while back and i cant find that thread nowhere. Like trace sizes to use with the amps and how far apart to put them.

Jim, i deleted the part and the whole trace and re added it and magnified the board to make sure it was connected. It still would not trace like i wanted untill i added juntion dots. The next one try doing just the pcb part and see if i can get anywhere like that without the schematic.
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obiwan
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Username: obiwan

Post Number: 1706
Registered: 12-2005

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Posted on Tuesday, 08 May, 2007 - 08:12 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Some of these PCB CAD programs will have "design rules" you can set. These determine how the traces will route (generally), like how close they'll be to other traces etc.... Look for those. But generally, the default rules should be good enough to get you going.

ARES (from labcenter), has a indicator that shows you where and how the traces will be routed as you place the components. It's only a general guide, not exact by any means.

As you put the component down (and already have a net list), you'll see the "rubber band" traces giving you an idea of how the traces will go, and there's also a yellow arrow pointer showing "something". I think it's the majority of traces and the direction they're headed.

One thing I do is lay a few traces and do an auto-route, and see how it works. If I sort of like it, I'll make a few changes to it and "accept it", or rip it up and try again.

But only route a few traces at a time. This way, you can more or less force certain things to happen. Force traces to go certain ways and places.

I find that to be easier than total hand routing, and much better than total auto-routing.

But yeah, they can be pretty dumb sometimes. The demo boards that come with the software must be something else, because I don't think you could ever design anything that actually routed that way and actually worked!!
Do Not Hit The Fly That Lands On The Tigers Head.
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xenington
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Username: xenington

Post Number: 21
Registered: 01-2007

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Posted on Thursday, 10 May, 2007 - 01:34 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

I sympathise with the problems you have encountered Scott - Eagle can be a law unto itself sometimes. But, keep an eye on the ERC and DRC and everything should be OK between the schematic and board.

In the schematic, it is best to use the little dots on every junction just to make sure. Also, if some components are changed, the 'straight line' connections may not be joined and can need dots as well.

The previous advice on auto-routing is good. Place the non-movable components where you want them and put the rest in a logical fashion inbetween. Do the important routes by hand and then let the auto-router finish off the rest. You will probably need to jiggle bits around to get the best solution. I aim for about 95% completion with the auto-router and do the rest manually using jumpers.

The Eagle auto-router has never made any mistakes for me (that were not in the schematic and my fault anyway), although it can come up with some pretty scenic routes sometimes. I just like watching it run (can you get it as a screen saver?) and betting on the % completion. Oh, the disappointment when your % drops!

I have never needed any more than the free version offers as the circuits I create are all quite simple, single-sided and small (<50 components). There may be better programs out there, but for a price tag of zero - Eagle is more than capable.
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magnum4
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Username: magnum4

Post Number: 479
Registered: 04-2005


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Posted on Saturday, 12 May, 2007 - 09:54 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

I delete the wire each time I make a change and run a new wire:-) I do use the autorouter and with care it does well :-))
But a bit of common sense works better:-) Thats why I run some tracks, and with a bit of juggling around can get it to rout well :-)

Incidently I almost always rout as single side.
HTH
Regards,
Jim
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scott2734
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Username: scott2734

Post Number: 192
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Posted on Sunday, 13 May, 2007 - 04:29 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

One more question. When i put a signal and im routing it, how do i get it to snap to a smaller grid? When im trying to place them, they go way too far, about half of that would be good. Iv looked in the prefferances and dont see a board grid in there other than the trace width and distance apart. thanks for the replies. Oh yeah, i oredered a book by al williams, maybe it will help me some too. He wrote the book using eagle.
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bob_scott
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Username: bob_scott

Post Number: 8
Registered: 04-2006

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Posted on Sunday, 13 May, 2007 - 08:30 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Scott,

I see your problem now. You must use the grid or there is no guarantee that the net lines will actually connect. Click on VIEW, then GRID to see tha radio button to diplay the grid. There are also options there to change the grid spacing.

I remember when working in San Jose, one CAD worker decided to take a massive ORCAD schematic off-grid in order to make things easier for herself. However this was a major mistake. Nets were missing connections. Another CAD designer had to redraw the thing and put all components and nets back on-grid. It was a 3 dimensional servo for a wafer inspection machine with about a thousand components! ...a 48 page schematic on 11 by 17...

Bob

(Message edited by bob_scott on 13 May, 2007)
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scott2734
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Username: scott2734

Post Number: 193
Registered: 10-2005

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Posted on Sunday, 13 May, 2007 - 07:33 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

No, when i say smaller snap position, i dont mean free hand. I am copying a pcb i got off the net while im trying to learn eagle. Sometimes i think its easier to copy other untill i learn the program and learn the best way to do things. Any way,the pcb im copying has 4 traces going under a 18 pin chip.When i try to put 4 traces with the same size and corners, i can only get 3 under the chip because they will not snap closer together.If i try to put 4, the last one is on top of the one before. I hope that clears it up some. Bob when you say nets, you mean the pin pads, right? I didnt change anything with that, they still look like there snapping on the pads right.
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xenington
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Username: xenington

Post Number: 22
Registered: 01-2007

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Posted on Sunday, 13 May, 2007 - 09:57 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Change the snap position on the board by doing the following:

View
Grid
Size - enter the value you want or click 'finest'. I think 1.27mm is default. Also, change the board measurements from inches to mm here.

You can make traces thinner by:

Edit
Change
Width - select a width smaller than the one currently set and click on the traces to change.

By the way, have you seen this link?

http://dmi.uib.es/~jguerrero/labSistemes/eagle_tut.pdf

Cheers
Dean
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magnum4
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Username: magnum4

Post Number: 492
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Posted on Sunday, 13 May, 2007 - 11:28 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Second Dean there ;-))

Also when routing you can put a smaller value in AUTOROUTING GRID. This will help rout tracks closer.
HTH.
Regards,
Jim

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