Custom Membrane Switches
This makes removing it
easy. Also, this particular
front panel is aluminum.
If you use a plastic front
panel, don't center punch
too hard or else you'll
break the plastic.
Photo 2. The paper work overlay is
attached to the front panel with a couple
of pieces of double-sided tape.
Photo 3. This shows the results — the PCB is
temporarily mounted to the front panel and
the work overlay has been removed.
Big Holes for
Photo 3 shows the
results. The PCB is temporarily mounted to the
front panel and the work
overlay has been
removed. Note that the
switch holes are about
0.5-inch in diameter. This
allows the switch body to extend part way through the
front panel. (Be careful with shorts to a metal front
panel.) If you use long actuator switches, still use about
0.5-inch diameter holes. This is because the overlay has
to flex a little. Holes that are too small won't flex very well.
You may want to experiment.
You will also have to adjust the spacing of the PCB so
that the top of the switch actuator is just about level with
the top of the front panel. In this case, a single nut provides the proper spacing.
trimmed-to-size overlay. If you have air
bubbles, carefully pierce the paper to let
the air out. Don't pierce the tape or else it will
eventually tear there.
Carefully place the overlay on the front
cover. This is the hardest part. You have to make sure that
the alignment is perfect before you press down. If you try
to move the overlay after it's stuck to the tape, it will
almost certainly tear. I shine a bright light behind the front
panel so that the holes shine through the overlay. This
makes alignment easier. Once you are sure the alignment
is correct, press the overlay down from the middle to the
edges. There is no easy way to remove air bubbles.
Trim away the excess double-sided tape. This should
look like Photo 5.
Attaching the Overlay
Remove the PCB and put double-sided tape on the
front panel. Use strips side by side, without any overlap.
Be sure that this tape is wider and taller than the overlay
— the excess will be trimmed off.
Again, extending the tape beyond the front panel
makes trim removal easier. Remove tape from all openings in the front panel. An Xacto knife works well for this.
See Photo 4.
Use the package sealing tape to cover the overlay —
and be careful — this step shows
any and all mistakes. (It's often
worthwhile to have several spare
paper overlays.) If the overlay is
wider than the tape, you can
either put the next strip side- by-side or overlap slightly (about
1/8-inch). If you overlap, try to
place the seam away from switch
Note, I find that putting tape
on the overlay and then trim-ming/cutting the overlay to size
from the paper easier than trying
to put tape on an already
Carefully cut through the overlay for the PCB mounting holes. Attach the PCB with the proper spacers. The
membrane switch should now work (see Photo 6). You
may want to experiment with the spacing to provide the
switch feel you like.
Variations and Notes
This particular version had only the switches on the
PCB. If you want to mount parts on
the PCB, there are two basic ways
to do that.
First, use tall actuator switches.
This allows parts to be placed on
the same side as the switches. This
requires longer spacers and obviously limits the height of the parts.
The second way is to put the parts
on the "back" side of the PCB.
However, in practice, it would be the
switches that are mounted on the
back of the PCB while the parts are
on the front.
But what about LEDs or dis-
Photo 4. Remove tape from all openings
in the front panel using an Xacto knife.