PCB design review/comments/suggestions etc.

I'm doing this design for a while now and before I send it to manufacture I'd just like to make sure everything is fine. The things concerning me the most are power connections and grounds so if someone could check that it would be most helpful. I'm using 12V external power supply for Arduino Nano and regulated 5V from Nano to power up everything else.

20121224.brd (205 KB)

What PCB software?

Eagle.

can't tell much from just the board
the schematic would help

in general avoid 90 degree bends in favour of 45 degree bends

mmcp42:
can't tell much from just the board
the schematic would help

I haven't made one, but most of stuff on that board is taken from tutorials:

4051 (left image, with only 4 "slave" chips) / 4021 / 74HC595 (without the cap on latch pins) / LM324 (with 2 comparators and therefore 2 outputs per HDD instead of three)

I've also added decoupling caps to 4051 and 74HC595 chips.

mmcp42:
in general avoid 90 degree bends in favour of 45 degree bends

I'm aware of that and I've tried to do so at most places. Can you link me some reasoning behind 45 vs. 90 degree bends?

no link (45 degree bends) but you're trying to avoid pockets where the etch can build up
45 degree bends have that effect

I also heard that the electrons can corner faster with 45 degree bends, but it was April 1st when i heard that :slight_smile:

that the electrons can corner faster with 45 degree bends

..maybe off the topic, but if you want to see the max frequency for a particular trace in your Eagle layout then simply double-click "length-freq-ri.ulp" in the ULP and you'll get a table with all traces and their max frequencies listed.. the more bends the smaller the max frequency.. :wink:
btw - the signal reflections (and stray capacitance) are lowest with round bends..

pito:

that the electrons can corner faster with 45 degree bends

..maybe off the topic, but if you want to see the max frequency for a particular trace in your Eagle layout then simply double-click "length-freq-ri.ulp" in the ULP and you'll get a table with all traces and their max frequencies listed.. the more bends the smaller the max frequency.. :wink:
btw - the signal reflections (and stray capacitance) are lowest with round bends..

that is a neat ulp
also shows maximum current per trace - now that IS useful!
thanks

Awesome indeed. Now back on topic! So like I said I'm pretty much only interested in whether my power connections / decoupling caps are wired correctly.

kustom:
Awesome indeed. Now back on topic! So like I said I'm pretty much only interested in whether my power connections / decoupling caps are wired correctly.

indeed but it's not easy to comment without the circuit!