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1
Grenzgenial – Speed of Light
V 0.00 3 November 2011
Markus Friedl [email protected]
Institute of High Energy Physics (HEPHY) of the Austrian Academy of Sciences www.hephy.at
2
General Description
“Grenzgenial“ is a German word which cannot easily be translated. A rather straight attempt would
result in something like “borderline ingenious”. This was the title of an exhibition to visualize borders
of all kind, and this was our contribution to visualize the speed of light limit involving the LHC. In
particular, the speed converges towards c even though the energy scale rises quickly. This nonlinear
behavior is demonstrated in an intuitive way by this exhibit.
Grenzgenial – Speed of Light is a desktop object which can easily be transported in a car. The
dimensions are given below. The object has an IEC connector on the rear and is operated by mains
power (<50W). A standard switching PC power supply is used, so it can normally operate in all areas
worldwide.
The user interaction is quite simple: A single rotating knob controls the status.
After power‐on or after a timeout period of approximately one minute, the object is in sleep mode.
Red LEDs around the knob pulsate in order to attract the viewer. Once the knob is touched, energy
and speed are displayed (starting from zero), and the beam rotation in the LHC is indicated by buried
LEDs. Moreover, a sound is played with a frequency depending on the present energy. The energy
can be ramped up to 7TeV, the maximum energy of the LHC protons. In certain regions, additional
panels in the center light up to indicate a comparison. As it is impossible to follow the LHC proton
circulation by eye already at low energies, another circle of LEDs arranged around the globe show the
speed if the LHC was as big as the earth.
% cElektronvolt (eV)
Geschwindigkeitder Protonen im LHC
Energieeines Protons im LHC
Etwa so schnell muss eine Rakete fliegen, um die Erde verlassen zu können 11 km pro Sekunde!
–
D i e H e l i o s -R a u m s o n d e n s i n d z i r k a s o schnell nichts, was der Mensch je gebaut hat, ist schneller!
–
U n g e f ä h r s o schnell bewegt s i c h u n s e r e M i l c h s t r a ß e durchs Univer-sum.
Fast so schnell wie das Licht! Die Geschwindigkeit steigt nun kaum noch, aber die Energie nimmt weiter zu.
Volle Energie des LHC! Ein Proto-ne ns t ra hl ha t nun die Wucht von über tausend r e n n e n d e n Elefanten!
Die Energie steigt am Anfang langsam, dann immer schneller, wenn Du am Regler drehst.So schnell würden die Protonen die Erde umkreisen.
km/h
Lichtgeschwindigkeit c = 299 792 458 m/s = 1 079 252 848.8 km/h
1 eV 1.60 10 J = 0.000 000 000 000 000 000 16 Joule
keV
Millionen
eV
Tausend
MeV
Milliarden
GeVTeV
Beschleunige Protonen im LHC!
638
mm
336 mm466 mm
Weight: approx. 20kg
Min
imum
rea
r si
de d
ista
nce
to w
all:
5cm
(ca
ble,
ven
tilat
ion)
Rubber feet. Loudspeaker is integrated in the base plate.
3
Electronics
Schematics, PCB layouts, assembly schemes, bills of material and a full set of Gerber files are given in
order to produce the PCB boards and assemble them. The LHC panel is composed of 2 layers, while
the front panel (main PCB) needs 4. Sizes and layer buildup are given in the zipped Gerber archives.
Please take care of the height of LEDs particularly on the front panel (see section “Graphics and post‐
processing” for details). The PIC16F84 must be placed on a socket in order to be programmed by a
PIC programmer and inserted into the PCB thereafter.
A few components need to be placed outside of the PCBs:
A standard ATX power supply (can be old, low power) is screwed onto the rear wall
An audio amplifier with an inductor (for power), a potentiometer and a damping resistor can
either be placed on the rear wall or on the base plate (see schematics for wiring scheme); the
audio signal is provided on a LEMO connector on the main PCB.
A speaker is placed on the base plate
The optical encoder is attached by a cable
A special serial cable (D‐Sub‐9 to IDC‐10) is necessary for initial flash memory programming
(see section “Firmware”)
Moreover, power and data cables are required between the two PCBs and the power cable for the
backlit panel (12V) is also attached to the main PCB.
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Firmware
Once the main board is ready, the firmware can be uploaded. The process described here does not
require the LHC board nor any external parts except for the power supply.
The firmware is divided into two parts: An Altera FPGA handles all the real‐time issues such as PWM,
LED orbits and sound generation, while the PIC microcontroller takes care of the higher‐level control.
Moreover, an 8 MBit flash memory is included on the main PCB which contains all the data for the
LED displays depending on the knob setting. This memory must also be programmed over a serial
interface.
The Altera firmware is provided as a schematics drawing and as a POF file. In order to program the
Altera onboard (using only the POF file), a ByteBlaster or USB‐Blaster device is needed. The board
must be powered when programming. Please note that the connector on the main board is possibly
smaller than the standard ByteBlaster plug, but the pinout is the same. Thus, a 1:1 adapter may be
required.
In a second stage, the PIC16F84 needs to be programmed using a PIC programmer. Just the HEX file
is sufficient for that, although the full sources are provided as well.
Finally, the flash memory on the main PCB needs to be programmed. This requires a Windows PC
with a serial interface (so far, we always used Windows XP, as Win 7 did not work well) to be
connected to the powered main board. A flat cable onto which a female D‐Sub‐9 connector on one
end and a female IDC‐10 connector on the other end are pressed (with matching pins 1) can be used
to establish the connection between PC and the main board (only RD, TD and GND are used; see
schematics for details).
The software to load the flash is written in LabWindows/CVI 8.1 by National Instruments, but an
installer package is provided for users which do not have this software installed. If you have, just
unpack the source archive which also includes the EXE file and run it. Otherwise, the flash program is
installed along with the required run‐time libraries.
When starting the software, you are asked to enter the serial port number. Then, this panel pops up.
First, load the CSV table provided using the leftmost button and the file selection dialog. Then, you
may click “Read Version” and “Read ID” in order to test if the serial connection works. The present
PIC firmware version should read 08 and the ID number is provided by the flash memory.
Once the connection is verified, hit “Unprotect”, “Erase Chip” (takes a few seconds if successful) and
“Download Sequence” (takes roughly one hour). The progress is indicated on the screen. In total,
2048 lines will be programmed. If the process is interrupted, it needs to be started from the
beginning.
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Mechanics
The frame of the exhibit is produced from off‐the‐shelf profile bars. We used the Bosch‐Rexroth
30x30 mm2 series, but similar objects are also offered from other companies. Our design relies on a
notch width of 8mm in the profiles at several locations; thus some alterations are needed if this
differs.
Mechanical drawings are provided, specifying the parts needed for assembly of the frame and the
panels to cover the sides: In the rear, a massive plastic plate (8mm thick) is used with an opening for
the power supply. The side panels are made from twin‐wall sheets and the bottom plate is a metal
matrix sheet, because a speaker is internally attached and it is also used as an air inlet.
The top part (showing and aerial view of the LHC) uses a commercial backlight display in A3 format.
Its name is “SlimLight classic (LED)” and it comes in various different builds. We use the model with
rectangular edges (not rounded) and a frame width of 33mm. The depth of the frame is 27mm. We
purchased the frame at the Austrian company www.tiedemann.at , but it seems to be available with
many other vendors as well. Moreover, we ordered a second plastic foil (normally put above the
printed sheet; Tiedemann part no. EFCL‐A3) so that we can put this foil on both sides of the printed
sheet (this improves the optical appearance of the buried LEDs). We also ordered additional pieces
of the same special acrylic plastic (it contains some additives that make it homogeneously bright)
that is used in the backlight display to be used for the comparison regions arranged in the center of
the display. The size of those pieces is 80x46x8 mm3; and five pieces are needed. The only thing we
did not need (and that is usually part of the delivery) is the power supply – we power the whole
exhibit using a commercial PC power supply.
Part numbers, quantities and lengths of the Bosch‐Rexroth profiles are given in the mechanical
drawings. Screws, mounting material and plastic covers are not listed explicitly, but should be
ordered as well (see photo on first page for some details). Moreover, it is highly recommended to
attach rubber feet to the base of the frame (also available from Bosch‐Rexroth). Depending on the
volume of the speaker, it may cause vibration and movement of the whole exhibit. Moreover,
scratches on the table can be avoided by rubber feet.
The knob (see drawing) for user interaction is glued into a pin (see drawing) which resides in a roller
bearing, part no. NKXZ7 from Misumi, www.misumi.de . That bearing is attached to the small plate
(see drawing) and the pin is eventually fixed with a circlip. The rotary optical encoder part (Bourns
EM14A0D‐C24 L064N) is attached to the pin using a small piece of semi‐flexible silicone tube. Please
have a look at the drawings to see how to assemble those parts.
A drawing is provided for the milling and drilling scheme of the front panel; moreover, the
coordinates of the LEDs are given in a Excel spreadsheets for both panels. In case of the LHC aerial
view, the holes are made into the acrylic plate of the backlit frame. A drawing shows the offset of the
PCB behind the panel to its frame. That PCB is attached to the acrylic glass by sticking the LEDs into
the holes. In the final assembly, some rubber foam can be put between the PCB and the rear wall to
gently press the PCB against the acrylic glass.
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Graphics and post‐processing
The two panels are shown here together with the names of the print quality files (300dpi). The front
panel is also available as an editable CorelDraw X4 file (requires the Myriad Pro font family).
lhcpanel.pdf frontpanel_graphics_en.pdf 420 x 297 mm2 424 x 264 mm2
Two panels need to be printed. As they are both illuminated from the back side, it requires a
backlight foil as offered by print shops. We used an Austrian company, www.digitaldruck.at , for this.
The product chosen is called “Backlight per m² Spezialfolie ultrahochauflösend” (ultra‐highres special
backlight foil): http://www.digitaldruck.at/produkte/grossbildtechnik/backlight/back/folie (costs
about 30€ for both panels, arranged on a single sheet and cut by yourself).
The LHC aerial will be put in the backlit A3 frame as is.
The front panel sheet, however, requires some
additional treatment. First, a hole needs to be
cut in the center of the red area in order to put
the knob axis through. Secondly, the white
areas for LEDs behind the acrylic glass need to
be made transparent. Those areas are
indicated in the picture to the right.
We used a soft cloth moistened by “Solvent 50”
(normally used to remove sticky labels; Farnell
part no. 1328070), a terpene mixture that washes away the white base cover on the otherwise
transparent backlight foil, but does not attack the printed colors. As production techniques may
differ, we cannot guarantee the same result with other vendors of backlight foil or cleaner.
In order to increase the brightness of the non‐lit parts of the panel, it is recommended to spray the
aluminum plate underneath the front panel with white color – except for the counter sunk holes
around the knob. These have 120° openings in order to make brighter lights and should remain
metallic. Thus, cover that area (shown in grey in the picture below) with masking tape before
spraying.
Finally, thin red and blue foil shall be put over the openings for the 7 segment LED displays to
improve the contrast. This foil can be obtained at stationery shops (we found suitable colors with a
pack of assorted transparent envelopes). The picture below shows the areas for blue and red foils.
keV
Millions
eV
Thousands
MeV
Billions
GeVTeV
7
A cross‐section of the front panel assembly is shown below. It consists of (outside to inside) a
transparent acrylic glass panel (3mm thick), the backlight foil, the aluminum plate mentioned above
(3mm) and the assembled PCB with the special acrylic glass in the centered part.
The special acrylic glass pieces (80x46 mm2, 8mm thick) are wrapped with self‐adhesive aluminum
tape on three sides (except for the side of the white LEDs which are bent by 90° to light up the acrylic
glass). Moreover, the back side (which resides on the PCB) is also covered with the foil. The first 10
mm next to the LED do not give homogeneous light and thus are covered under the aluminum plate.
Sockets are recommended for the 7 segment LED displays to bring them closer to the backlight foil.
The LEDs should also be mounted in such way that they reach the correct height (11mm above PCB).
Cover this area when spraying white paint
Tape blue and red foils to enhance contrast of 7 segment LED displays
3.0
0 m
m
3.0
0 m
m
8.00
mm
Square LED(5 x 5mm) Bent white LED
Single Digit LED (Display) on socket (9.6 x 13 mm)
Display field 63 x 37 mm(usable for picture + text)
67.00 mm
80.00 mm
10.00 mm
41.
00
mm
Aluminum
Acrylic glass
Special Acrylic Glass*
* wrapped with self-adhesive Aluminum tape on sides (except where LEDs are)and on back to increase brigthness
Backlight foil
Blue or red foil above LED digits(attached with tape to aluminum sheet)