My first PCB design.
Nov 27, 2008 at 8:57 AM Post #16 of 34
Quote:

Originally Posted by rembrant /img/forum/go_quote.gif
I suppose your talking about the 90's that are still there.


No, I'm talking about everything that isn't a 45 or a 90. 90's are justifiable for natural T junctions and a few other places. Use 45s everywhere else.

EPCB doesn't have a mode to snap to 45s like, say, EAGLE. But, it's not hard to see when you're at a perfect 45: the stairstepping on the trace edges will go away. Technically there's still stairstepping, but it's so tiny -- one pixel up, one pixel over, repeat -- that it more or less looks smooth.

Quote:

I don't see what harm they can do.


As I said, the electrons don't care. It just looks nicer. If you're going to go to the effort and expense of burning boards, shouldn't they look nice?
 
Nov 27, 2008 at 5:09 PM Post #18 of 34
Quote:

Originally Posted by tangent /img/forum/go_quote.gif
No, I'm talking about everything that isn't a 45 or a 90. 90's are justifiable for natural T junctions and a few other places. Use 45s everywhere else.

EPCB doesn't have a mode to snap to 45s like, say, EAGLE. But, it's not hard to see when you're at a perfect 45: the stairstepping on the trace edges will go away. Technically there's still stairstepping, but it's so tiny -- one pixel up, one pixel over, repeat -- that it more or less looks smooth.

As I said, the electrons don't care. It just looks nicer. If you're going to go to the effort and expense of burning boards, shouldn't they look nice?


Ahh, I see! I wasn't aware that the dithering would transfer over to the actual part. I have redone any traces that where not 45 or 90 angles. They do look better.
biggrin.gif
I have also figured out how to properly fill the surround of the pads on the top layer that connect to the ground plane. I have also moved around some of the labels to make them look better.

Should I add some caps to ground from V+ and V-? It might take a little jiggering but there is no reason that I couldn't fit a place for a couple ceramic caps on the power pins.
 
Nov 27, 2008 at 7:34 PM Post #19 of 34
Quote:

Originally Posted by rembrant /img/forum/go_quote.gif
I wasn't aware that the dithering would transfer over to the actual part.


It won't. They either use vector art when making your boards, or much higher resolution bitmap art.

That said, even on the final piece, 45s still look better, at least to those accustomed to looking at PCBs. Like any art form, there are schools of practice and esthetic guidelines that are best broken only by an expert. For instance, the SO-8 to DIP-8 adaptation traces on the PIMETA aren't 45s, but it's beautiful. Why? Because Morsel's an expert, with a sharp esthetic eye. Until you develop an artistic style of your own, best to go with what works.

Quote:

I have also figured out how to properly fill the surround of the pads on the top layer that connect to the ground plane.


They're not fully connected for a reason. The more copper immediately connected to a pad, the longer it takes to heat it all up with an iron; meanwhile, the component whose leg your iron is touching is also cooking. The tiny little reduction in conductivity here is totally made up for by the ground plane as a whole.

If anything, I'd say you should widen these "thermals", to allow faster soldering. Check the EPCB options to see if that's possible.

Quote:

Should I add some caps to ground from V+ and V-? It might take a little jiggering but there is no reason that I couldn't fit a place for a couple ceramic caps on the power pins.


Why not? It will increase your options for chip choices.
 
Nov 27, 2008 at 8:12 PM Post #20 of 34
Quote:

They're not fully connected for a reason. The more copper immediately connected to a pad, the longer it takes to heat it all up with an iron; meanwhile, the component whose leg your iron is touching is also cooking. The tiny little reduction in conductivity here is totally made up for by the ground plane as a whole.


Thats a good point.
I would be soldering these things on the bottom anyway. I only fully connected the trace on the top layer. Seeing as how they are plated through holes though, I might have to go back and change it again.

Edit:
LOL chock one up for the nooby not knowing what a thermal pad was. Thanks Tangent. I took care of that in about 2 seconds.
 
Nov 28, 2008 at 5:20 AM Post #21 of 34
I have made some more changes.
1. I decided that there was really no advantage to the resistor divider in this amp so it has been removed completely.
2. The power cap has been changed to accommodate a Panasonic FC series in 470uf 25v. The 3.5mm diameter variety but the 5mm diameter should just squeeze in there no problem.
3. Added A small bit of trace and pads for .1uf ceramic decoupling caps from V+ and V- to ground.
4. Board size is now 1.4"x1.325"
5. Added some personalized artwork.
6. The amp has been named Cool Button by my wife when she saw my artwork.

Edit: Layout replaced with the newest one available.
 
Nov 29, 2008 at 5:53 AM Post #22 of 34
Alright folks, I have worked out a BOM for this and of course some things had to change again. The standard service from Express doesn't Include silk screen. Even so, I have cleaned up a few of the silk screen patterns to make it look better and less cluttered.

The major difference comes in the form of two huge poly caps with giant lead spacing.(15mm OMG) They threatened to cover up my sophomoric art work and I just couldn't let that happen. Did I mention that this thing was tiny?
biggrin.gif


Anyway, here is the BOM and I will repost the layout in place of the one in the above post.

1x 470uf 25v aluminum electrolytic **(Panasonic FC 3.5mm)** $0.53 P10274-ND
2x .1uf ceramic capacitor **(Vishay/BC)** $1.96 for 10 BC1114CT-ND
2x .22uf poly cap **(Optional DC Blocking caps)** $1.28 P3224-ND
2x 1k 1% metalfilm resistor **(Vishay/Dale)** $0.29 CMF1.00KQFCT-ND
2x 100k 1% metalfilm resistor **(Vishay/Dale)** $0.29 CMF10.0KQFCT-ND
2x 50k 1% metalfilm resistor **(Option for R5)** $0.29 CMF49.9KQFCT-ND
2x 100k 1% metalfilm resistor **(Vishay/Dale)** $0.29 CMF100KQFCT-ND
1x OPA2132 DualOpamp Dip8 $5.40 OPA2132PA-ND
1x TLE2426 Voltage divider TO-92 $1.30 296-1994-ND
 
Dec 3, 2008 at 3:43 AM Post #25 of 34
Just wanted to get a final OK on this before I send it off.
First, I added thanks where they are due. Tangent pretty much kept this from being a total disaster so I added some some remarks in copper. I also included the web address here. I hope that is appropriate. Unless there are any objections, they shall remain.

It's not terribly important that this be perfect. I intend to redo this whole layout in eagle later so I can use a cheaper PCB manufacturer and get a silk screen. I have never had a board made before so lets just hope the extra money express charges relates to higher quality.

Edit:
See post #32 for new layout.
 
Dec 3, 2008 at 4:02 AM Post #26 of 34
Okay, just some I clear: R5 is between the bottom traces and the output points (for example, between the hole to the left of R5 and OUTL).

You may want to put another through hole there for the wire to come off the board. Otherwise your going to either have R5 or a jumper and a wire trying to come off the same point.
 
Dec 3, 2008 at 10:05 AM Post #28 of 34
Quote:

Originally Posted by rembrant /img/forum/go_quote.gif
Which one of these caps is better for an input cap?


The ones with Zs at or near the end of their part number have funky crimped legs. The crimps help keep the cap in place during soldering, but that's more an automated assembly concern. I'd go with the straight legged one.

Quote:

First, I added thanks where they are due. Tangent pretty much kept this from being a total disaster so I added some some remarks in copper. I also included the web address here. I hope that is appropriate. Unless there are any objections, they shall remain.


Um, well, thanks. Not necessary, but okay.
smily_headphones1.gif


Quote:

I intend to redo this whole layout in eagle later so I can use a cheaper PCB manufacturer and get a silk screen.


Good plan.

Quote:

I have never had a board made before so lets just hope the extra money express charges relates to higher quality.


No, the extra money goes to pay for that "free" software and the convenience of their slick operation. I'd call ECPB's board quality good, but not exceptional.

For the same money, you can get better quality with mask and silk. The downside is that you may have to pay for software to do it, and it'll take more effort.

This from the guy whose shop currently has boards from probably 4 different manufacturers, including EPCB.

Quote:

Not sure why but the forum forces the top and bottom layer pics into JPG sorry for the fuzziness.


There's a size limit to attached pictures. JPEG can be much smaller than PNG -- JPEG compression is variable, whereas PNG is fixed quality -- so perhaps that's what had to be done to get under the threshold.

If this is what's happening, you need to spend more time in a graphics tool optimizing your PNGs so they fit. There are a lot of PNG optimizers out there, which do more than just remove colors. You can squeeze maybe 10% of the bits out of a PNG this size with one. My favorite is Save For Web in Photoshop, but there are much cheaper options. If you're willing to get down to the command line, I'd recommend pngcrush which is free and works very well. It's readily available on Linux, can be had on OS X through Fink, and on Windows through Cygwin.
 
Dec 3, 2008 at 1:35 PM Post #30 of 34
What's with the big gap in the ground plane under the opamp?
No capacitors from the rails to the ground? That is the return path of the current from your headphones to keep your ground low Z at high frequencies, the TLE cant do it all by itself. These caps and TLE should be right where the ground return comes in as well, else it has to go right through where your sensitive feedback loop is
 
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