> Dwayne Reid wrote:
> > I'm trying to keep this daughter board as narrow as possible so as to
> > not block viewing of status LEDs that are on the main board.  That
> > means that the rows of resistors are going to be close together.
> =

> How about put holes in the daughter board so you can see the LEDs thru it,
> then make the daughter board as big as needed, working around the LED hol=
es?
> =

> =


You can also put holes (or slits) between the pads to create a clearance an=
d =

thus a much larger creepage distance.

There are a lot of factors that determine the minimum clearance and creepag=
e =

distance:

Type of insulation - Basic, reinforced or double, which in turn depends on =
the =

accessibility of the electric conductor in the circuit and how a fault will =

affect other accessible conductive parts or circuits.

The pollution degree for the circuit board.

The CTI (Comparative Tracking Index) for the material where conductor is in =

contact with (in this case the PCB).

For a homogeneous construction where the conductors are shaped in a way whi=
ch =

reduces the dielectric strength between them (no sharp edges) the distance =
for =

clearance can be decreased. This does not apply for mains circuits.

The altitude in which the circuit can be used. Higher altitudes gives longe=
r =

required insulation distances.

The rated impulse voltage (transients) for mains circuits or circuts derive=
d =

from mains circuits.

If the circuit is part of a measuring circuit (an instrument) there are als=
o =

other requirements.

/Ruben


=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D
Ruben J=F6nsson
AB Liros Electronic
Box 9124, 200 39 Malm=F6, Sweden
TEL INT +46 40142078
FAX INT +46 40947388
ruben@pp.sbbs.se
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D

-- =

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