Re: gEDA-user: powermeter board, with less ground planes :-)

[Joerg <joergsch@xxxxxxxxxxxxxxxxxxxxx>]

DJ Delorie wrote:
>> Much better. If you want to be extra good provide another 0.1uF
>> parallel to the AVDD caps, close to pin 3.
> 
> The problem is, there's no ground near pin 3.  The Vdds are all near
> pin 1, and the GNDs are all near pin 10.
> 

Isn't that whole outside perimeter plane GND? Currently you have the far 
side of C13 via'd to that. It's just that C13 is kind of far away from 
pin 3.


>> Might want to rotate C11 and squeeze it in between R18/C12 so it's
>> closer to pin 4. But that really only matters if you expect lot of
>> RF from cell phones and stuff.
> 
> Nope.  It's inside a metal box with all the circuit breakers.
> 

That makes it pretty safe. But I did have a situation at a client where 
this wasn't enough. Cell phone noise made it in via the cables. GSM 
phones and BlackBerries were the worst for some reason. We fixed it by 
switching to a device with clean CMOS inputs instead of BJT and 
providing a nice little 0603 cap smack dab across the diff input, as 
close as design rules would let us.


>> Some day maybe you could post the whole schematic so folks who are new 
>> to gEDA like me can test drive a schematic with hierarchical order. 
>> Somehow I never managed to find the Scandinavian example.
> 
> The two *.sch I posted are all there is; I have a Makefile that just
> renames the one channel to the other fifteen of them.
> 

That's cheating :-)


>>> 495 parts so far!  367 holes, 290 of which are vias.
>>>
>> If it's any comfort my board that is in fab right now has 585 parts :-)
> 
> Yeah, but I have to assemble mine all by hand.
> 

I just sent my stuffing punch list to the tech at this client for the 
prototype. I bet she wasn't happy when she opened that email.


>> Question: IIUC you haven't had the board produced yet. How did you 
>> create this nice rendering of a finished circuit board?
> 
> PCB's png exporter has a "ben-mode" option (yes, we need to rename it)
> that does photorealistic output, with a little post-processing:
> 
>   pcb -x png --ben-mode --dpi 450 powermeter.pcb
>   pngtopnm powermeter.png | pamscale 0.333333 | cjpeg -q 90 > ${WEB}/powermeter.jpg
> 

Sweet! Thanks, I'll copy this hint right to the new gEDA wiki file here. 
And I'll show my layouter. He currently uses PADS but who knows.

-- 
Regards, Joerg

http://www.analogconsultants.com/



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