Elektor EPROM, Руководство пользователя

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GENERAL INTEREST
53 11/2002 Elektor Electronics
as that for the solder side. The film should
however be printed in a mirror image. Apart
from that, it is recommended to remove any
unused pads. Especially with ICs it is difficult
to see which pins are used once the socket is
mounted on the board. When the unused
pads are removed, only the remaining pads
need to be soldered. Some PCB design soft-
ware supports this feature. Layo1 for exam-
ple has the facility to export the design as a
ment impossible. After the glass has
been cleaned with white spirit or
benzene, it can be glued onto the
frame with a small amount of two-
part adhesive.
Alignment
The most important part of the light-
box frame is the alignment mecha-
nism. This should not have any play,
be adjustable over a certain range
and remember its position when both
frames are taken apart. This sounds
more difficult than it is in reality.
To help with the alignment we
can use a stay-peg from a window
stay. There are various types of these
available. What we need is a straight
pin with a diameter between 6 and
8 mm, which has been welded to a
base plate. The pin should have a
rounded top, which makes it easier
for the top frame to slide on.
The second part of the alignment
mechanism has to be homemade out
of a piece of aluminium.
Figure 2
shows all the relevant dimensions;
the hole on the left fits over the stay-
peg. This could have been a round
hole, but then this should have had
the exact size of the pin to avoid any
play. This is practically impossible to
make, hence the choice of a V-shape.
The angled sides will take up any
play in the X and Y directions.
The slot in the right-hand side
allows the slider shown in Figure 2
to move freely round the bolt in the
top frame. Two of these sliders are
required. The holes can be easily cut
out of the aluminium with a fretsaw.
Again you should de-burr all sides
with a file.
Construction
All parts are now ready to be put
together.
Mount the two stay-pegs onto the
bottom frame, preferably with coun-
tersunk M4 bolts (about 10 mm long)
and dome nuts. For the top frame
you should use two M5 lock bolts
with a length of 20 mm; an accurate
tap with a hammer should be
enough to fix them in their holes. If
you don’t want to risk breaking the
glass you can use a small flat file to
turn the round hole into a square.
A slider is placed over each of the
bolts followed by a large washer and
a wing nut, allowing this to be eas-
ily loosened and tightened.
Figure 3
shows the alignment mechanism of
the prototype in detail. The light-box
frame is now ready for use.
The films
The artwork film for the component
side can be made in the same way
Figure 1. Dimensions of both frames.
Figure 2. The slider of the alignment mechanism.