Printed Circuit Board (PCB)

[tim10243]

hi,
after hours of soldering wires on an experimental board I came to the
conclusion that it would be much more effective to make a PCB which is
not so expensive as I thought at the beginning.
now i tried to design a board with the software EAGLE which is for
free in a light version. you gonna find my board at:
www.eyris.net/spot/trigger_tim01.brd
I would be happy if an expert here would take a couple of minutes to
check this board and to take a look if I made some mistakes. if the
board is ok and some of you are interested in it I could order some
more. I would like to order the boards here:
http://www.mikes-elektronikseite.de/
and the price would be round about 5,- euro per board as far as i can
see.
Tim

[tj]

I took a quick 10 second look at it. Just a few things I noted.

1) You layed out ISP1 and ISP2 side by side.
2) Try to avoid running traces below the RFM12 module. If possible,
make this a ground plane.
3) If you are sending this to a fab house, you will need to include
board dimensions. I believe this is layer 20.
4) You might want to widen your ground traces and Vcc traces
5) Depending on the antenna you plan to use, you might want to double
check to make sure you left yourself enough clearance.
6) Consider placing Fire/Quench near the optoisolators

Terry

[Mathe]

Hi Tim,

Like TJ said, try to widen your traces; these are too thin.
Also you shouldn't run the antenna on the board but connect it as
close as possible to the RF module.
Some of the traces run too close to eachother or soldering islands.
try to put C1 as close as possible to the pins of the atmega.
Also add an extra 0.1uF as close as possible to the Vcc and GND pins
of the radiomodule.
Make sure you have this double sided board metalised from top to
bottom otherwise it will be very hard to solder some components.
But if this your first try I think you've done well :)

Marc

[tim10243]

hi tj,
hi marc,

thanks for your time. yes its my first try and after getting into the
program its a little bit of fun too ;-)
here is my second try - i didn´t trusted the eagle-auto-function this
time and made it myself - i hope i did better this time ;-)
http://www.eyris.net/spot/trigger_tim_02.brd
I made some minor changes to the circuit:
- There is no GND and VCC connection to the display anymore as I´ll
connect the display outside of the board to the battery
- There is no GND connection to the shutter and there is no LED on the
board as well, as they will be connected elsewhere too
- I changed the C2 elko capacitor into another one because the one
used in the original .sch is as big as the Atmega
According to your comments:
- There are no traces below the radiomodule anymore
- The Fire/Qench connections are close to the optocouplers now
- There is a 100nF capacitor at pin 9 + 10 of the radiomudule now
- The capacitor C1 is close to the Atmega now
- The antennapoint should just be an connectionpoint for the cable
coming from the antenna but I can´t find a single connectionpoint in
the eagle library
- The traces now are 0,016 wide - which size do you think they should
have?
take a look at let me know abut your opinion

Tim

[tim10243]

Oh, I forgott: the dimensions of the board!
I tried to find out where to make this settings in eagle but I couldn
´t find anything.

On 20 Nov., 14:13, tim10243 <t...@brakemeier.info> wrote:
> hi tj,
> hi marc,
>
> thanks for your time. yes its my first try and after getting into the
> program its a little bit of fun too ;-)
> here is my second try - i didn´t trusted the eagle-auto-function this

> time and made it myself - i hope i did better this time ;-)http://www.eyris.net/spot/trigger_tim_02.brd

[tim10243]

I made the traces a little wider now (0,025), doublechecked the
connections, changed positions of some elements,
and now I hope I made it :-)

http://www.eyris.net/spot/trigger_tim_02.brd

if you think this one is OK, we could offer this board layout as a
download here

tim

[Till Seyfarth]

Hey Tim,

 

nice work - thanks! I'm sure it'll work (thanks to Terry and Marc as well). I'm occupied with other stuff right now but I'll look at your design for guidance as soon as I continue with my SPOTs.

 

I'd like to give you write access to the documentation wiki... easiest way to get your experiences to everyone who's following this project. Interested? 

 

Cheers

Till

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[tim10243]

hi till,
of course - I would be glad to share some of my experience
tim

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> > .

[Mathe]

Hi Tim,

The last board you've made is not correct.
The track coming from pin 5 of the atmega is crossing the tracks from
pin 7 and 8 of the mega on the same layer. That means short circuit!

Marc

> > > spot-developme...@googlegroups.com<spot-development%2Bunsubscrib­e...@googlegroups.com>

> > > .
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[tim10243]

hi marc,
thats exactly why I was asking if some of you could have a look at the
layout.
4 eyes see more than 2 as we say in germany! thanks a lot!
here is the correction:
http://www.eyris.net/spot/trigger_tim_03.brd
tim

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[tj]

Hi Tim. I replied yesterday, but for some reason my post didn't show
up. I think it may be because I included a link that diagrammed how to
build an AVR ISP cable. I will try to remember the comments I made...

How do you plan to program the micro? I only ask because of where you
places ISP1 and ISP2. If you are planning to use a standard AVRISP
cable, then you will need to reposition these. Do a google search for
avr isp cable and click on the first link.

Regarding dimensions, you can comment on the board size using the
measures layer (Looks like your board measures 1.75 x 2.6.). This
isn't really that important though. The important part is layer 20,
which you have already taken care of.

The trace width is fine.

I am not sure what your plan is for powering the LCD. Are you using
the same battery to power the LCD as the board? Are you designing a
separate circuit for it? You will want to make sure the board and the
LCD share the same ground!

One last thing that you might want to think about. Even if you aren't
planning to use a connector for some of the signals, (like vcc and
ground for the LCD) you might want to have a via or soldering pad for
these just in case you decide later to use the board for these. You
don't need to use them, but you can can always solder wires to these
points later if needed.

Tj

[tj]

Tim, how do you plan to program the micro? I only ask because of the
odd way you are laying out ISP1 and ISP2. If you are using a standard
cable you will want to fix this. A picture is worth a thousand
words... http://www.scienceprog.com/yet-another-simple-avr-isp-cable/

Regarding dimensions, it looks like your dimensions for the board are
1.75 x 2.7 inches. You can use layer 47 (measures) for documenting the
board size if you want, but you already covered the important part
(layer 20).

Your trace sizes are acceptable.

Not sure how you are powering your display, but make sure you use the
same ground as the rest of the circuit.

TJ

On Nov 20, 5:13 am, tim10243 <t...@brakemeier.info> wrote:
> hi tj,
> hi marc,
>
> thanks for your time. yes its my first try and after getting into the
> program its a little bit of fun too ;-)
> here is my second try - i didn´t trusted the eagle-auto-function this

> time and made it myself - i hope i did better this time ;-)http://www.eyris.net/spot/trigger_tim_02.brd