SparkFun Forums

[davep238]

Why does the input cap need to be rated at 400 volts? This seems like serious overkill to me. BTW, what is the voltage rating on the power supply caps (C17, etc)?

And to make the traces look nice, only use 45 and 90 degree angles. And while some people will say not to use 90 degree angles at all, 90 degrees will work out OK, especially for your wide traces.
-Dave Pollum

[SpikedCola]

To be honest I dont know. Its supposed to be a high-quality cap, Im just following the original design in terms of parts. The power supply caps are rated at 63v.

Is there any way to have Eagle auto-rename all the parts, so it changes U3 to U1, and starts again at R1, C1, etc

EDIT
Next revision with straighter traces:


Just outta curiosity, I ran it through the DRC bot on BatchPCB and the production price is <$8, way better than $40 for the original gerbers

[FartingMonkey92]

I just thought i'd mention that you may have trouble mounting the LM3886
on your heatsink, as the tab isn't off the outline of the board...

As the creator of the original project did, i like to use bars to clamp devices to
heatsinks rather than relying on the tabs of them to make proper contact, with
a unpunched piece of Mica and thermal compound, you gain superior electrical isolation...

Oh, and it looks like you have an airwire on the surface-mount capacitor...

[SpikedCola]

Thanks for pointing out the airwire! Turns out I had a trace under the pad that didnt get ripped up when I manually routed some other ones.

As for mounting a heatsink, I was planning to use a heatsink that was just large enough to cover the back of the chip, but protruded towards the back of the case and perhaps even out the back - I personally dont think it will be a problem mounting, however I trust your judgement and I moved the IC towards the back of the board (as far as I could without moving the power trace off the board). I actually like this layout better as it gives me more room for the larger input signal capacitors

v1.2:


Also, still wondering how to rename all the parts automatically if possible. How would I go about adding tNames to the silkscreen? Would that be part of the cam processor?

EDIT I also moved the caps and connectors down a bit to give me room if I decide to go with a larger heatsink

[FartingMonkey92]

"How would I go about adding tNames to the silkscreen? Would that be part of the cam processor?"

That is to do with the CAM Processor... Oddly, i have actually just posted about that to someone else 'round here!
BTW, your getting a good layout there...

[metsfan]

Sorry, I don't have anything to add about helping you lay out your board... I just wanted to say it's been awesome following this thread and watching the design come together from all the great people helping in here.

That is all. Carry on.

[bigglez]

As for mounting a heatsink, I was planning to use a heatsink that was just large enough to cover the back of the chip, but protruded towards the back of the case and perhaps even out the back.
...
I actually like this layout better as it gives me more room for the larger input signal capacitors
...
v1.2: (image deleted)
...
EDIT I also moved the caps and connectors down a bit to give me room if I decide to go with a larger heatsink

Your layout is much better than previous versions!

I would swap the location of the power connector and
the two large caps. In the physical world you may have
trouble inserting or removing the connector due to the
caps height and the heatsink hardware.

I don't see any "breezeway" between the caps. You
should plan on the cans being oversize in EAGLE, as we
have discussed several times earlier. Better yet, buy
all the components before sending the PCB to China
for fab, and use a caliper to measure accurately.

A PCB that is too tight for parts is nothing more
than a "green coaster" for your coffee mug!

[SpikedCola]

[bigglez]

Image deleted

(1) Cap on top left is not in line with cap on top right?
(2) How tall are these caps?
(3) How much space is needed for the IC mounting hardware?
(4) There are no mounting holes on the PCB?
(5) "U3" is the only designator in the silk screen layer?

[SpikedCola]

- aligned
- added holes (heatsink will be mounted to case to hold up back side of board
- I was planning on using the hole in the IC tab, however I may experiment with an aluminum bar once I have it assembled
- turned on tNames layer
- caps are 35.5mm tall