42. Backbox Toppers
Toppers are extra decorations on top of the backbox.
Some real pinball machines included toppers as original equipment, but
not all that many. I'm not sure if the manufacturers were intentional
about using toppers sparingly just to maintain the novelty value, but
if they were, I think was a wise move. The machines that had them
tended to stand out from the crowd.
In more recent times, pinball collectors have become fond of adding
toppers to machines that didn't have them to start with. After-market
toppers are probably the biggest category of "mods" for sale these
days. Everyone's home collection seems to have a topper on every
Virtual cab builders like their toppers as well, but for different
reasons. In the real pinball world, toppers are mostly about novelty
and decoration. In the virtual world, in contrast, toppers tend to be
more about function and less about decoration. There are certain
feedback devices that just won't fit anywhere else: fans and beacons,
or example. We tend to view the topper area as an extra platform for
But I think it's worth also looking at the topper the way that the
pinball collectors do, as a decorative element. We all put a lot of
effort into our cabs and want them to be as great as we can make them,
so I think it's worth thinking about how we can extend our visual
themes to the topper. I think it's a nice addition to make the topper
an extensions of your cabinet art, rather than just a bunch of gadgets
bolted on top.
Let's start with a look at how some of the real machines used toppers
to enhance their visual theming, to get some ideas about how we can
do the same thing.
What makes a good topper?
Pinball collectors these days are fond of adding toppers to all of
their machines, so if you search for "pinball topper", you'll find all
sorts of options for sale. In my opinion, though, a lot of these
after-market add-ons aren't very imaginative. The mod sellers want to
make a buck, so they'll package up any toy vaguely related to a game's
theme and call it a topper. You also see a lot of toppers for sale
that are little more than signs reiterating the game's title, or
copying some graphics from the backglass.
I think most of the better ideas for toppers can be found in the
relatively rare cases of toppers as original equipment.
My favorite examples from the real machines are the ones that not only
fit the theme, but take some physical element from the theme and
render it as a full 3D object. This can extend the 2D artwork of the
backglass into the 3D world the machine inhabits, and can create an
impression of the pinball machine itself as the object of the theme.
Perhaps the most perfect example is the taxi cab roof sign from
Taxi (Williams, 1988). It's accomplishes that extension of the
theme into the real-world surroundings that I mentioned, creating an
impression of the pinball machine as a taxi cab.
Along the same lines, a number of police-themed pinballs over the
years featured rotating beacons, or even complete police-car light bars,
as toppers. Police themes are nearly as overused in pinball as in
CBS dramas, so there are lots of examples, but a canonical early
example is High Speed (Williams, 1986):
A beacon isn't just a passive decoration, either. It can be an active
part of the game action, lighting up and spinning in sync with events
in the game. It's no wonder they used these over and over on the real
machines. They even used them in a few cases where it's hard to see
any relation to the theme. One particularly curious example is
F-14 Tomcat (Williams, 1987), which had not one, not two, but
I don't know who at Williams thought that police-car beacons had
anything to do with fighter jets; maybe someone had a notion that the
U.S. military theme called for something red, white, and blue. More
likely just a marketing mentality that more is more. At any rate,
it's understandable why Williams used beacons so often, since they add
not just an extra decoration, but also a functional element, in the
form of a light show.
Another great functional topper is the fire bell on Fire!
(Williams, 1987). It's the sort of bell you'd expect to see on an
antique fire wagon, so like the Taxi sign and High Speed
beacon, it creates a suggestion of the pinball machine as the central
object of the theme. And like the police beacons, it's an active part
of the game's sensory effects, being equipped with a solenoid hammer
that rings the bell when certain events occur in the game.
Yet another brilliant functional topper is the cloud-shrouded fan on
Whilrlwind (Williams, 1990). It's the perfect active toy for
the theme; the fan activates during multiball modes and other events
in the game, creating a tactile sensory effect from the blowing air.
It even fits the rule about being something suitably "on top" in the
real-world context of the theme, albeit in a more abstract way than
the previous examples. The enclosure is meant to look like a cloud,
which is a sort of top of the weather.
The Whirlwind fan is also an example of a second method for
making a topper feel well integrated with the theme, which is to
make the topper an extension of the backglass artwork into the space
outside the canvas. Whirlwind's backglass art depicts a big
storm brewing, so the cloud-shaped topper can be seen as a continuation of
that artwork into the space above the backbox. We see this approach
much more explicitly in the topper on The Addams Family
(Midway, 1992), where the topper's whole function is to complete the
mansion depicted on the backglass, whose peaks poke out above the top
of the backglass and into the clouds.
(Williams, 1990) didn't have a topper as original
equipment, but there's a DIY add-on topper I really like. The idea is
to take a vanity mirror light - the kind with a row of big round
bulbs, like in the stereotypical actor's dressing room - and populate
it with party bulbs in assorted colors. Put it on top with the bulbs
pointing up. I've seen this idea mentioned a couple of times on the
pinball forums, and I'm not sure who came up with it first, but one
nice example is
Photo courtesy of Heinz-Peter Bader
It's especially interesting to compare this design to the various
after-market commercial toppers for Funhouse that the "mods"
companies sell. The bulb topper works so well because it's perfectly
in scale and it so nicely captures the carnival atmosphere of the
theme. It creates an impression of the pinball machine as Rudy's
ticket booth, the way the Taxi roof sign suggests the pinball
machine as taxi cab. In contrast, the commercial topper products I've
seen all just reiterate something from the theme: one is a giant
"Admit One" ticket, another is a cut-out of Rudy. They do nothing to
pull the artwork into the real world.
Virtual cab toppers
Virtual cab builders usually focus on the functional backbox elements.
As a result, there's a fairly standard set of feedback devices that
most cab builders incorporate in their toppers:
Most cabs have at least one of these, and many use all of them.
They're all great additions functionally. Beacons, flashers, and
strobes all make nice light shows, and a fan adds a wonderful tactile
element that movie theaters might call a "4D experience".
But does a big pile of toppers make for a "theme"? Well, from one
perspective, it actually does. One way to see a virtual cab is as a
whole collection of pinball tables in one. So you could say that the
theme is "all the pinballs" - which makes "all the toppers" a fine
fit to the theme.
Personally, I like the idea of giving a virtual cab some kind of theme
beyond "all the pinballs". I discuss that idea a bit in
. If you are
giving your machine a theme
that's not just "all the pinballs", I think it's also a nice touch if
you can extend your theme to the toppers.
Of course, you'll still want to choose which active elements to
include based on functionality. I'd never suggest that you should
forego a fan just because fans don't have any obvious relation to your
theme. But maybe you can work some of the functional elements into
your theme. For example, on my cab, I came up with a custom plastic
enclosure for the fan that's meant to look like a star-burst, to go
along with the outer space theme of my cab graphics. So I didn't
really try to make the functionality of the fan fit the theme, but I
did at least try to work its shape into the visual layout. (If
you're interested in my specific topper design, you can find some more
Some ideas for how to work your toppers into a theme:
- Brainstorm for natural real-world "topper" items fitting your theme,
like Taxi's sign topper.
- Think about custom enclosures for one or more of the items. The fan
is perhaps the most obvious enclosure to customize (like I did on my
cab), since you need some sort of enclosure anyway, and it's easy to
build around a bare motor-and-blade fan core. You could also create
your own custom covers for beacons or strobes, or work them into a
larger enclosure like a police-car light bar.
- Consider versions of the topper devices or exterior finishes that
fit your theme. For example, if you're using a steam-punk theme, give
your toppers a Victorian industrial look, with brass finishes and
The Pinscape topper
The topper design that I came up with for my own pin cab is very
specific to my theming, so I doubt it'll be of much interest to most
pin cab builders other than as one more example. But in case anyone
wants to reproduce it or use it as a starting point, here are some
details about the design.
Most of the topper is made from off-the-shelf parts:
- A row of five standard pinball flasher domes with high-power RGB
LEDs inside is arrayed across the front edge. These are simply wired
in parallel with the main flasher board at the back of the playfield,
so they always light up at the same time and in the same colors as
the main flashers. See Flashers and Strobes for details on setting
up a standard flasher panel.
- A pair of Peterson 771 dome-shaped rotating beacons, one in red and
one in blue.
- A pair of "22 LED white strobes" that you can find on eBay.
See Flashers and Strobes.
The centerpiece is a custom-built fan with a 3D-printed plastic
The fan is built with a generic 12V DC motor with a 1/4" shaft, mated
to a press-on plastic blade from a microwave oven. The specific blade
I used is Thorgren model number 6C2504C1, in black. This happens to
be the same OEM part that Williams used for Whirlwind, which
also features a topper fan, so I was delighted to be able to use the
exact same part. But don't worry if you can't find the same thing;
eBay has lots of similar fan blades that look just about the same.
Just look for a 6" fan blade with four find, with a shaft bore that's
the same size as your motor's shaft. A good search term to try
is 6" fan blade.
To mount the fan motor, I rigged a simple bracket using sheet metal. I
don't have any tricks to suggest here; the bracket I came up with
isn't particularly clever or elegant. You just need something that
you can attach to the motor body to hold it at the right height above
the backbox roof.
For more on building a fan like this from parts, and for details
on how to wire a fan to your output controller, see
The fan enclosure is designed to fit between the beacon domes, to
create the impression that the enclosure and domes are connected. The
area around the fan opening is meant to suggest a blazing sun, in a
sort of cartoonish style.
You can download 3D plans for my fan enclosure in STL format here:
Note that the ZIP file contains "front half" and "back half" models in
addition to the full model. I created the half models to fit the
limits of the specific manufacturing process I used, so these probably
won't be useful unless you happen to use a printer with very similar
constraints, but I included them just in case.
There's one more detail worth mentioning: the fan enclosure is decked
out with lighting. (If you want to see it in action, I made a short
The fan enclosure includes has two types of lights. The first is one
of the common 5050 RGB LED strips, installed around the perimeter of
the front fan opening. This is the same type of LED strip normally
used for under-cab lighting
. If you look
carefully at the fan enclosure model, you'll see a little lip on the
inside of the opening, about 1 centimeter deep. That's the mounting
surface for the LED strip. The strip is mounted on the inside of this
lip, so that the LEDs face inwards towards the center of the opening.
This creates a nice ambient light effect inside the fan. This strip
is simply wired straight to the undercab lighting strips, so it shows
the same colors as the undercab lights. This works best if you have
DOF set up to use the "undercab complex" effects; that program changes
colors in response to game events, so it makes the fan interior
lighting fairly dynamic.
The second bit of lighting installed in the fan consists of nine
high-power RGB LEDs, arranged around the perimeter of the opening,
facing forward. Again, looking carefully at the STL model, you'll see
a small circular hole in each of the "points" of the star-burst shape.
These holes are the right size for typical 3W RGB LEDs, of the same
type commonly used for RGB flashers, but in this case, without
the aluminum "star" base that's usually used for the flashers. You
can find these LEDs on eBay by searching for "3W RGB LED" - they look
These are actually the same LEDs used in the "star base" type. The
only difference is that they're sold as bare LEDs, not mounted to the
aluminum heat sink base. The procedure for wiring them is the same as
for wiring the flasher LEDs; see Flashers and Strobes
for more on
The method I used to mount the LEDs in the fan enclosure is inelegant
and a little tricky (it takes some manual dexterity and a bit of
patience), but it worked well and has held up well over the several
years since I built it. I started by soldering hookup wire to the
LEDs, with just enough wire between adjacent LEDs to reach from one
hole to the next. The LEDs are wired in series, meaning that
the "+" side of one LED connects to the "-" side of the next LED, and
so on down the chain. There are no resistors in this chain - just the
wires and the LEDs. Once all of the wiring was soldered, I arranged
all of the LEDs into the desired locations, poking out through the
star-burst holes. This is the part that requires dexterity and
And now for the part that's truly inelegant. To secure the LEDs in
place, I stuffed some packing foam into the pockets behind the LEDs.
I tried some other approaches, the best hope being 3M VHB tape (which
is pretty amazing for many similar applications), but that didn't
work; it's hard to get anything adhesive to stick to 3D-printed
plastic, since the surface tends to be uneven and powdery. The
packing foam turned out to work surprisingly well, and it has the nice
feature that it's easy to remove if any of the LEDs ever needs to be
replaced or if a solder joint ever breaks.
Controlling the 3W perimeter LEDs is almost a whole separate project.
There are two main parts:
- The first is the power supply for the 3W LEDs. Wiring LEDs in
series means that you need to supply them with a voltage that's higher
than the sum of the VF ("forward voltage") values for all
of the LEDs. For 9 of the 3W RGB LEDs, this works out to about 33V.
So I used a DC-to-DC step-up buck converter to convert power from a
12V supply to 33V. (You can find such step-up converters on eBay;
they run about $10 for the size needed here.)
- The second part is something to control the LEDs. You could just
wire them to your DOF output controller, and assign them to one of the
existing DOF device types, such as the strobes or under-cab lights. I
wanted something a little unusual, though, which required some more
custom electronics. What I wanted was to coordinate the LEDs with
both the strobes and the beacons: when the strobes fire, I want the
LEDs to flash white, and when the beacons run, I want the LEDs to
flash rapid red and blue patterns like a modern police cruiser. You
might be able to produce something like this with DOF directly,
but it seemed easier in this case to build a little microcontroller
project instead. As usual with microcontrollers, GPIO pins provide
the connections to the outside world: GPIO input pins connect to
the DOF outputs for the strobes and beacons, so that the controller
can monitor DOF activations on those devices, and GPIO output
pins connect to the fan LEDs, via MOSFETs. I wrote a small custom
program for the microcontroller that watches the input connections
from DOF, and when it sees one of them activate, it generates the
appropriate light show on the fan LEDs.
The ZIP file linked above (with the 3D design for the fan
enclosure) contains a hand-drawn schematic for my controller
circuitry, and the C++ control program for the Trinket. The
program is designed to be compiled and downloaded into the
Trinket with the Arduino IDE. I apologize for the rough
appearance of the schematic; this is directly from my original
working notes, and I haven't had a chance to clean it up
into a proper presentation.
Reviewing this circuit plan with fresh eyes, I see a couple
of changes I'd suggest, if you plan to deploy this in your own cab:
- Add a diode (1N4007 should work
nicely) in series between each optocoupler cathode
(pin 2 of the PC817) and the DOF output controller port,
with the striped end of the diode on the DOF port side.
This will avoid any danger of feeding back the beacon/strobe
supply voltage into the optocoupler LED. (LEDs don't typically
have very high reverse voltage tolerance on their own.)
- You might need to add a capacitor, connected
across the Trinket power supply pins, to filter
electrical noise from the rest of the system. You'll
know this is necessary if the Trinket randomly resets
or behaves erratically; if it's stable, don't worry
about this. If you see any glitchy behavior, try
adding a 0.1uF capacitor with its leads connected
to the Trinket's BAT and GND terminals. Position
it as close to the Trinket as practical.
If erratic behavior persists, try different size
capacitors, even up to large sizes like 1000uF.
Sometimes two capacitors in parallel work even
better than one, such as a 0.1uF and a 100uF.
(Larger capacitors, 100uF and above, are
usually electrolytic, which have a "+" and "-"
side, so be sure to connect the marked "-" lead
to the GND terminal. Smaller "disk" capacitors
aren't polarized. See Capacitors for
more if you're not sure.)
Note that my circuit design doesn't use conventional
current-limiting resistors for the LEDs. Instead, it uses
a feedback loop on the MOSFETs to throttle the current through
the LEDs. I did it this way mostly because I was curious
about how to create a current-limiter circuit like that.
I don't think it's all that much better than the simpler
approach with ordinary resistors, since ultimately it's just
using the MOSFETs as variable resistors and burning off
the extra power as heat, just as fixed resistors
would. But it seems to work nicely, and it does have the
slight advantage that you don't have to figure out the right
resistor size for each channel; the feedback circuit
amounts to a little analog computer that does the math
for you each time you apply power.