How does my quad H-Bridge/simple sensors board look so far?

[corrado33]

I know, it's a very tedious task.  But I figured I'd ask, and try to wring some information out of  you guys.  

Anyway, I'm not done yet, but I've finished with the H-Bridge chips and power etc.  Now I just need to route the MCU stuff and I'll be good to go.  I don't have much else to do.  (Although I'll probably add a bunch more headers like admin did on his axon.  Yes, I know it would be MUCH easier to actually buy an axon, but I like doing this kind of stuff.  Then I can say, I made that, all of it (when I actually finish the bot  ).  I actually find routing really fun and rewarding.  When you step back and look at it you're like wow, that really works.  

I'll try to make it easy for you, so I'll provide pics of the layers, and the eagle file for you to view.

Yes, I still do need to assign some values for some caps and what not, I know that.  I also need to add small caps across the motor pins (the GIANT connectors, you can't miss them.)

Here is a link to a (big) pdf of the schematic.  I didn't know how to make it smaller and it'd look too tiny on a small Letter paper or whatever.
http://www.box.net/shared/xpsqp4tt2oa55kjkan58
EDIT:  Hm, you can actually just go to that link and look at the PDF, no need to download it.  Cool.

Here is a link to the board in eagle.
http://www.box.net/shared/1xhfy22y8jhruk48o28i

And here is a link to the schematic in eagle.
http://www.box.net/shared/vmfzy900htsv8hz7t7jz


Here are the pics (for those too lazy to download the files above  ) (Or those who don't have eagle)
Click for full size.

Parts and pads.  (Sorry you can't read most of the names)


Both Layers


Bottom layer


Top Layer

EDIT:  And the eagle light limitation of 3.5x4 inch board is KILLING me.  
EDIT2:  And I might switch some things around.  I might flip the second fuse and move the caps and vreg up a bit to give me more room for the MCU.  And see those two lone blue traces going to the left dual H-bridge right below the two motor connections?  I might put those on the top layer so that the ground plane can extend into there. 

[lrmall01]

I think you might be onto something with moving the micro up.  It would make it easier to fan out the signals without having to worry about the edge of the board.  Then again, most of those look like they are no connects so it really doesn't matter.

[corrado33]

I think you might be onto something with moving the micro up.  It would make it easier to fan out the signals without having to worry about the edge of the board.  Then again, most of those look like they are no connects so it really doesn't matter.

Well I can make the traces go as far out as I want, even outside of the 3.5 x 4 inch eagle boundary, so that board boundary there isn't really where it's gunna be.  I just can't move the micro any further down cause of the limitations of eagle light and I was using that line to mark my lowest position.  

Yes, most are no-connects, but I would like to put as many as possible onto header pins so I can expand it.  Really I'm just building the locomotion part of pseudo ERP.  (Like admin's experimental robot platform.)

EDIT:  Moved the caps up and placed the grounds inward toward the regulator ground, and moved the LED up and out of the way, much more room now. 

[Graynomad]

I don't think the eagle board size should cause you a problem, there's so much room there you could drive a truck through  

To help even more you could ditch all the resistors/transistors used to invert the L298 signals and just use a hex inverter.

EDIT: Also, do you want to lose half the processor speed by running with the internal oscillator?

______
Rob

[corrado33]

Yes I know there is a lot of room, but I've only made a couple of boards, so I'm trying to keep the traces and tolerances as big as possible.

And yes, I'll PROBABLY add a crystal or some sort of external oscillator.  If not for speed sake, more for stability's sake.  I don't really NEED the speed, so I'll probably keep it reasonable.  Plus it'll be less noisy and consume less power. 

I looked at hex inverters.  The thing is, while the resistors do take up a bit of space, they really aren't a problem for me, so I'll probably keep it that way for now. 

[corrado33]

Phew, geeze surface mount chips are a pita to route.   

Anyway, I've finished my board..  I'm just going through the electrical rule check and stuff now.  There are a TON of errors, all due to my header pins being too close to the edge of the board, which isn't a problem because my board will actually be slightly bigger. 

There are also a few tiny "tolerance" errors here and there, nothing big enough to worry about though.  Also a couple of overlap errors, but that's because while the fuses have two pins per side, they only have one "pin" in the schematic. 

Ok so I've attached the pics and eagle files.




Any suggestions?  I'm sure I've made (at least) a few mistakes.  For example, on datasheets for 3 pin ceramic resonators, it says the middle pin is usually ground, but eagle yells at me for it?  Did I wire that in right? 

And the schematic hasn't changed much from above, I just added a bunch of headers, and I don't feel like uploading it again...

[Graynomad]

What's the pinout on the 3-pin headers?

There's a quasi standard that is GVS (Ground, Volts, Signal), using that would allow a lot of things to plug in directly.

______
Rob

[corrado33]

What's the pinout on the 3-pin headers?

There's a quasi standard that is GVS (Ground, Volts, Signal), using that would allow a lot of things to plug in directly.

______
Rob

Ahhh, I did not know that.  I actually have it VGS.  The only reason I did that was because the ground plane would extend to the ground pins this way instead of the other way around.

That's an easy fix though.  I'll probably just solder the +5V pins on top and let the ground plane extend on the bottom. 

Thanks.