Hi guys I designed a project that utilizes a 328P surface mount chip and before I get the boards made I was hoping someone could look over my schematic and board layout and let me know if you see anything that need changed. When I was breadboard prototyping I had to put a pull up on the rx pin otherwise the program would not run.
This board will be installed in a vehicle so I need to make sure everything can handle the voltages and noise that is in the automotive enviroment.
Need more decoupling caps on the '328P VCC pins. Best would be one each on 4, 6, 18. So you're two short.
Flip C1 so it's on the other side of that wire or add another cap there. You have given it a commendably short connection to the chip on the positive wire but the ground return path is very long. The decoupling caps need to be close to the ground pins as well as the power pins.
We can't see the back layer of the board.
On the schematic, ground symbols are not expensive. You could double or triple the number of ground symbols and eliminate the long horizontal wires.
"12v switched" near the top left has no obvious leader going off to the side. If it wasn't labelled like this, then it would not be obvious that this has a connection elsewhere on the schematic. Why is the whole circuit switched through this relay? You can consume serious amps off 12v-switched in most car systems. I would not use the relay unless my outputs are switching more than 10A. If they were, I'd have a fuseholder on the board too.
What does D10 do? Prevents RPS from powering the +12V line when the relay is energised?
Why D3 and D5.
They do nothing if reverse input voltage is 12volt, and release smoke if reverse voltage is 13volt.
You have already a reverse voltage protection (D2).
I would change all 1N4007 diodes to 1N4004. Faster, and less forward voltage.
D4 should be a TVS diode. Zeners are bad at clamping power spikes.
Leo..
Hi,
I would change all 1N4007 diodes to 1N4004. Faster, and less forward voltage.
I can't find a data sheet that indicates that.
Tom.....
Turn-on time is indeed not in datasheets. Turn-off time is.
Read this article/link in post #6 regarding snubber/kickback diodes.
http://forum.arduino.cc/index.php?topic=332674.msg2295816#msg2295816
Apparently the 4001-4004 are manufactured differently from the 4005-4007
The differences are only small, but still..
Leo..
