From: Andreas Robinson (sleeper75se_at_yahoo.se)
Date: 2002-01-29 18:54:05
Hello,
A question for Jim and Joerg, or anyone else who has
the knowledge:
I have completed all the layouts, but there are some
rough spots left. I've attached an image that shows
part of the layout on the ADC-board.
To the left, labeled U200, is the ADC, and to the
right, labeled U201 is the microcontroller.
At the bottom of the picture you see three grey pads
labeled VIN-, GND and VIN+ where you connect the
power, +/-5 volts.
Now, for the question: How should I route the ground
trace in the center?
Should it stay the way it is, going directly to the
ground pins (13-14) on U200
or
should I connect it directly to the analog ground
plane to the left
or
the digital ground plane to the right?
or
fill the whole surface below pins 13-14 with ground
plane, letting all currents flow whichever way they
want?
Any suggestions are greatly appreciated!
If you feel you need more details, please let me know.
Status report on my project:
I've managed to cut the costs a bit. Changing the
filter to 4th order (needs higher sampling frequency,
but that is a good tradeoff) and reducing the number
of different part types has allowed me to reduce the
cost to around $145 for a 2-channel device, and $195
for a 4-channel device.
The input stages would cost around $28 each, if you
could buy resistors and capacitors from Digikey in
singles. That's not possible now, so the actual cost
will be higher.
The ADC-part, including the fiber-optic receiver,
costs about $60-$80 (depending on how you count those
resistors and capacitors) so a cheaper 10-bit variety,
using a TinyAVR and regular opto-couplers could
possibly save $40 on the 2-channel version.
Regards,
Andreas
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This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:37 BST
