I designed a PCB. What''s wrong with it?
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--- In basicstamps@yahoogroups.com, "jmccorm" <jmccorm@y...> wrote:
> --- In basicstamps@yahoogroups.com, "fab4442003" <fab4442003@y...>
wrote:
> > The possible problem I see the spacing between the LED holes -
which
> > looks too close. Typically you want to place the holes the same
> > distance apart as the LED leads. You'll find this info in the data
> > sheet for the LED - it's typically 0.10 in.
>
> Even for a 5mm RGB LED with 4 pins? (I *thought* I got it right,
but I
> could be wrong!)
Check the data sheet. it is not uncommon to have the outer pins bent
to reach the wider holes.
Please don't think I'm being harsh, and these are my opinions, not
some industry standards.
My critique is that you have some huge trances and some tiny traces.
The large traces only need to carry the max current of all the tiny
traces.
I opt for 20 mil traces when the space allows and 80 mill pads if I
am not going to put traces between pads.
Of course I lean to the mechanics of mechanically etching a board and
not photo engraving.
I try not to have traces angle from pads, but rather to have them
come straght out before angles.
R-1 is located so as to force pins 4,5,6 and 7 to angle on exit. R-1
only needs to be 1/4 watt or even 1/8 watt so the traces are much
larger than required.
and with the smaller resistor, you can relocate the holes so as to
have less angles on the traces.
Also, since you have 3 resistors for each LED, I would group the
resistors in lots of 3. Running them around the mounting hole is no
biggie, but for troubleshooting it is much easier if the layout is of
components aligns with the devices they serve.
all the above is opinion. If the logic is correct, then the board
would be fine.
The only real caution I offer is that the key be moved a little bit
off the close proximity of the DIP. If you chose to use a chip
carrier, it will have a wider footprint than the chip and the key and
chip carrier could interfere with each other. The DIP package
outline may be wide enough for any carrier, but you do have room, and
a little extra space might make the difference between a simple
project and darn later on.
I have been making boards for people (mechanically etched aka-routed)
and I concern myself with the details.
A recommendation is to print out the board 1:1, lay the printout on
some foam board and press in the components. you'll find some parts
have too much room and others are too close. Seeing a mock-up give
one a whole different perspective.
Dave
> --- In basicstamps@yahoogroups.com, "fab4442003" <fab4442003@y...>
wrote:
> > The possible problem I see the spacing between the LED holes -
which
> > looks too close. Typically you want to place the holes the same
> > distance apart as the LED leads. You'll find this info in the data
> > sheet for the LED - it's typically 0.10 in.
>
> Even for a 5mm RGB LED with 4 pins? (I *thought* I got it right,
but I
> could be wrong!)
Check the data sheet. it is not uncommon to have the outer pins bent
to reach the wider holes.
Please don't think I'm being harsh, and these are my opinions, not
some industry standards.
My critique is that you have some huge trances and some tiny traces.
The large traces only need to carry the max current of all the tiny
traces.
I opt for 20 mil traces when the space allows and 80 mill pads if I
am not going to put traces between pads.
Of course I lean to the mechanics of mechanically etching a board and
not photo engraving.
I try not to have traces angle from pads, but rather to have them
come straght out before angles.
R-1 is located so as to force pins 4,5,6 and 7 to angle on exit. R-1
only needs to be 1/4 watt or even 1/8 watt so the traces are much
larger than required.
and with the smaller resistor, you can relocate the holes so as to
have less angles on the traces.
Also, since you have 3 resistors for each LED, I would group the
resistors in lots of 3. Running them around the mounting hole is no
biggie, but for troubleshooting it is much easier if the layout is of
components aligns with the devices they serve.
all the above is opinion. If the logic is correct, then the board
would be fine.
The only real caution I offer is that the key be moved a little bit
off the close proximity of the DIP. If you chose to use a chip
carrier, it will have a wider footprint than the chip and the key and
chip carrier could interfere with each other. The DIP package
outline may be wide enough for any carrier, but you do have room, and
a little extra space might make the difference between a simple
project and darn later on.
I have been making boards for people (mechanically etched aka-routed)
and I concern myself with the details.
A recommendation is to print out the board 1:1, lay the printout on
some foam board and press in the components. you'll find some parts
have too much room and others are too close. Seeing a mock-up give
one a whole different perspective.
Dave