CA2050891A1 - Display - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A display comprises a static unit (8) on which is mounted a rotating unit (7) driven by a motor (12). The rotating unit carries light emitting diodes (6) arranged as vertical columns which sweep around a cylindrical surface. The light emitting diodes (6) are controlled by a control circuit (6) in accordance with data stored in a memory (61) so as to provide a cylindrical display. The control circuit (60) and memory (61) are located in the rotating unit (7) and the memory (61) has a capacity for storing several different images for display.

Description

~ 23~ PCT/~B90/~

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DISPLAY.

The present invention relates to a display.

A known type of display compris~ a static base unit and a rotating unit driven by a motor. The rotating unit carries a plurality of light emitting d~odes (LED's) which are controlled during rotat~o~ so as to provide a display image.

EP 0 026 762 discloses a display of ~hiC type in which a rotating two dim~nsional array o~ LE~'~ sw~ep~ a cylindricaL volume and the L~D 's are controlled so as to defi~e a cylindrical thr~e dlmensional array of picture elements (pixels). Data for co~rolling illumination of the pixels is sent in serial form from fixed electronics in the base uni~ via a~ rared link ~o rota~ing electronics in the rota ing unit. The rotating elec~roni~s essentially comprise a decoder for illuminating each L~D of the array in s~quence, with no da~a storage bein~ provided in the rota~ng unit. Thus, only one L~ a~ a time can b~ illuminated.

GB Z 093 617 and EP 0 156 544 di close di~plays of this type a~ whlch two diametrically opposite vertical columns o~ ~ED'8 ~w~ep a common ~ylindrlcal display surface and the LED'~ ar~ ~ontroll~d so ~ to de~ine a cyllndrical two, dimensional array of pix01s. The rotating unit con~ain~ enough ele~ronic~ and ~ory ~or all of the LED's to be controlled simultaneou~ly and for data to be stored for all of ~he pixel~ to provlde one complete image. In order ~o: charlge the display~d imag~, a connection has ~o be established with ~che rotating unit so ~hat n~w data can be writ~en in~o the memory. Durlng such reprogra~uning, ~che display cea~e~ to, function as a display un il the old data have be~n replaced by the new .

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data. Thus, dispLay images cannot be changed during normal operation of the display. This make~ image updating and animation dif~icult or impossible and requires expert or tra~ned personnel to reprog~mme the display .

Another pr~blem with knowll display~ of this type is that the light output i~ relativ~ly low. Thus, shaded locations are necessary f or viewing such displays .

According to a first aspect of the invention, there is provided a display comprising a static unit a~d a moving unit, the moving unit carrying a plur~lity of light sources and being arranged to move so that the light sourceC perfonm a repea~ed mov~ment, the moving uni~
including a memory for storing data for providing a plurality of displayed images and control mean for control~ing the light sources so a~ ~o displ y at least ona selected image at a time.

The moving unit is prefer~bly a rotating unit and the ligh~ source~ are pre~erably arranged as a plurality of co}umns parallel to the axis of rotation. The light sources ar~ pr~erably ligh~ em~tting diode~.

~h~ s~at~c unit i5 prefera~ly arrang~d to co~municate w~th ~he moving unit by mean~ of a communicatlon link, such ~8 a ro~ry transforner. Preferably the static unit co~a~n~ a further memory ~or storing da~a ~or a plurali~y o~ ~ur~her displayed imag~ and transmission means for tr~smi ting ~he data to th~ ma~ory and the con~rol mean~ of the moving unit via the co~munication link.

It is ~hus possible to provide a display which perm ~ s sev~ral ~m~g~es to be displayecl ln a de~ired sequence, f or ~) 90/12354 PCI/GB90/00564 2 ~ g l instaslce . o a~s to change the image~ or so a~ to prov~de animated images.

According to a second aspect of the irlvention, there is provided a display comprising a ~tatic unit and a rota~ing unit, the rotating unit carrying a plurality of columns of light sour~es arranged to sweep a ~ommon cylindrieal sur~ace, the liyht sour~es of each colwmn being oriented parallel to each o~her at an angle to a radius ~rom the axis of rotation through th0 column and the light source of ~ leas~ two of the columnR being oriented at respective different angles.

In g~ner~l, light sources such as light emittlng diodes emit most of ~heir light ~orwards along their optical axis, with the llght intensity falling with incr2asing angle ~rom the axis. By varying ~he orientatlons of the columns, it is possible to provide a oylindrical image wh~ch remain~ vlsibl~ close to ~he extreme~ of the cylindric~l surface which are visible from any one point.

At leas~ two of the COlUmn8 may be o~fset relative to ea~h other paralle} ~o the ro~ational axi~ so as to provide interlacing.

According ~o a third aspec o~ th~ inven~ion, th~re is provld~d a d~splay, comprising a static unit, a rotatlng ~un~t c~rrying a plurality of light source~, a motor for drlving th~ ro~ati~g unit, and a con~rol circul~ for controlling the ~p~ed o~ the motor, the control circult comprising means for repeatedly pre~etting a counter to a pre~e~ valu~, m~ans for s~epping the coun~r towards a pred~termin~d value at a predetermined rate for a period rela~ed to the pe~iod of rota~ion of th~ motor, and means for ~upplying increased power to th~ mo~or when the counter reache~ the predetermined value.

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Such a syctem provides highly accura~e motor Rpeed control and, by using stable or similar clocks to control the ligh~ sources a~d the prede~ermined rate, dispenses with the need for any kind of synchronisation between the static and rotating units.

According to a further aspect of the invention, there is provided a display according to any combination of the first to third aspects of the inve~tion.

According to ~ fi~th aspect of the invention, there is provided a motor speed controller compxising means for repeatedly presetting a counter to a pre~et value, means for stepping the counter toward a pxedetermined value at a pred~termined rate ~or a period related to the motor rotation period, and means for supplying increa~ed motor power when the counter reaches the predeter~ined value.

The inve~tion will be ~urther de~crib~d, by way of example, with r~erence to the accomp~nying drawings, in which:-Figure 1 i~ an external view of a display constituting a : pre~erred embodiment of ~he invention;
::
Figur~ 2 shows the di play o~ ~ gure 1 with ~ch~ caseremoved;

Figure ~ i~ a side view of part o~ the display of Figure lj, Figure 4 is a plan view of ano~her part of ~he display of Figure 1;
:
Figure 5 i~ a diagrammatic plan view o~ th~ part of the di~play ~hown i~ Figur~ ~;

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Figuxe 6 is a block schematic diagram of the display of Figure 1;

Figure 7 is a circuit diagram of a display card of the display of Figure 1;

Figure 8 is a block circuit diagram of a rotating control CiICUit of the display of Figure l; and Figure 9 is a block circuit diagram o~ a motor control arrangement of the display of Figure 1.

The display 1 shown in Figure 1 comprises a cylindrical case having opa~ue upper and lower parts 2 and 3 separated by a transparent middle part 4. A plurality of display cards 5 is visible through the transparent part 4, with each display card havi~g at its radially outer edge a vertical column of thirty two light emitting diodes 6.

As shown in Figure 2, the display cards 5 are mounted on an upper unit or carousel 7 which is rotatably mounted on a lowsr base unit ~. The cards 5 are supported hetween a lower carousel plate 9 and an upper carousel plate 10, which Garrie8 display control electronics on a control card 11. The carousel 7 is mounted on th~ shaft of a dr1ve motor 1~ which is fix~d to the base unit a . The base unit 8 has a base pla~e 13 rigldly connected to an upper plate 14 by spacers 15. The p~ate 13 also carries var~ous circuit boards, such as 16, 17, and 1~, and a serLal por~ inpu connectox 19.

As shown in Flgure 3, the base plate 13 provides a moun~ing for a support plate 20 which is mounted by means of pillars 21. Th~ motor 12 is moun~ed to the support plate 20 by means of pillars 22.

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The m~tor 1~ has an output sh~ft 23 which extends abov~
and below ~he motor. The shaft 23 is made of metal or o~her electrically conductive material and is provided with a slip ring 24 which co--operates with a pair of brushes mountPd in brush holders 25. The brushes are connected to the common ox earth line of a power supply mounted in the base unit 8.

The upper part of the motor shaft 23 is provided with another slip ring 26 which is electrically insulated ~EDm the shaft. The slip ring 26 co-operates with a pair ~E
brushes mounted in brush holders 27. The brush holders 27 are fixed to a support plate 28 which is fixed by pillars 29 to the top of the motor 12. The brushes co-operating with the slip ring 26 are connected to a positive voltage output of the power supply in the base unit. The motor shaft and ~he slip ring 26 are connected to a power supply unit of the carousel 7 as will be described hereinafter.

A rotary transformer is pro~Jided for transmitti~.g data from the base unit 8 to the carousel 7. The r: :ary transformer comprises a fixed assembly 30 mounted on the support plate 2~ and a ro~ating assembly 31 mounted on a carousel support hub 32 provided with a ~oss 33 and fixed to the mo or sh~ft 23. Each of the parts 31 and 32 of the rotary transformer comprises a ferrite ring ~upporting a coil or winding.

Fi~ure ~ shows the arrang~ment of display cards or circuit boards 5 mounted on the carou~el support hub 32.
Each circuit board S is provided with a support frame 34 for support and for connection to the hub 32. The columns of light emit~ing diodes 6 are mounted on LED
; brackets 35. Sixteen display boards 5 are provided and are arranged as two groups of eight boards with the first set being conn~cted to a ribbon cable bus 36 and the , 90/12354 pcr/GB9o/~os64 $ ~ ~

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second ~et being conne ::ted to a ribhon cable bus 37 .
Display board collnec:tors are shown at 3~ and power supply and data connections rom 'che slip r~ ng~ 24 an~ 26 and f rom the rotary tran~:f ormer secondary winding cr part 31 are indicated at 39, 40, and 41.

Figur~ S illustrates diagraaunatically the po~itions and orien at ions of th~ column~ of ligh~ emittirlg diodes with respect l:o the axi~ 42 of rotatiorl of the carous~l. Th~
columns; o~ ligh~ emitting diodes are labelled by numbers f rom 1 to 16 inside circles . The COlllIlU19 are equi-angularly spaced 2!bou~c the circun~erence of the carousel such that the arlgle a between each adjacent pair of columns is equal to 22~. The arrows in Figure S
indicate the optical axis of each light emitting diode ir the columns, with the axes o~ the light emit~ing diodes in each column being parallel. Thus, the light emitting diodes ln the colulM labelled "1" are orien'ced at an angl~ of ~ anti-clockwise with respect to a radius pas3ing through the column, whereas the axis of the column "2" is displaced by an angl~ ~ clockwise with resp~ct to the radius through the colu~n. The orientations of the axes of the other columns are as shown in Figure S and, in a pre~err~d embodim~nt, the angl~ 0 i~ 12 and the angle ~ i~ 48. Such an arrangeme~ otnpensate~ f or the li~ited angular dl~per~t or~ o~ llght from the ligh~ emitting d~odes to eith~r ~ida~ of ~he optical axls, and par~its light f rom ~h~ display to be rec~ived by a vlewl3r for substantially the whol~ of thQ~ part o~ th~ cylindri~l surf~e described by ~chQ column~ o~ light eMit~cing diodes f aclng th~ viQwar. In practice , the purtion o~ th~ cylindrical surface whl~h is visible and fro~ which li~ht can be se~n is less than but close to 1~0, for instance about 160' .

In order ~o provide a mul~ colour im~g~, columns of red light emitting diodes and column~ of green light em~ n~

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diodes are provided. Thus, the columns "l", "4", "6",~
"7", "9", "12", "14", and "15" consist entirely of red light 2mitting diodes, whereas the o~her columns consist entirely of green light emitting diodes.

Further, the light emitting diodes in all of the columns ar~ arranged to have a common pitch and the columns "l", "2", "3", "6", "7", "8", "l2", and "l3" are arranged at the same height so that the n-th light emi~ting diode in each of these columns follows exactly theOsame circular path. The remaining columns are also at;,~e same height as each other but are displaced upwardly--with r~spect to : the above mentioned columns by half the pitch of th~
light emitting diodes. Thus, the sixteen columns provide an interlaced display to improve the vertical resolution of the display.

Each of the columns "l" to "16" can thus be displaced from the local radius by one of tw~ angles and in one of ~wo directions, can be one of two colours, and can be in one o~ two interlaced groups. This gives sixteen posslble combinations of parameters and all sixteen . combina~ions are present in the sixteen columns of light emitting diodes.

As will b~ d~scribed hereinafter, the display i~ arranged to p~ovide 512 discrete circumferential picture elements (pixels). In order ~ox the circ~mfere~tial display : definition to b~ the same as the vertical definition, the pitch of the light emit.ing diode in th~ columns is made equal to the circumference divided by ~56 (th~
interlacing of the display giving the same vertical resolu~ion as circumf erential resolution ) .
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Figure 6 is a block schematic diagram of the electronics in th~ sta~ic or base unit 8 and the rota~ing unit or ~123~ PCTIGB90/M~4 carousel 7. A single block 5 represent~ th~ sixteen display cards.

A mains input co~nector 43 is connected to a power supply unit 44 w~ich supplies power to the electronics in the base unit 8 and, via the slip rings 24 and 26, in the carous~l 7. In addition, the mains input connector 43 is con~ected to a motor speed control circuit 45 which controls the supply of power to the motor 12 and controls motor speed by means of a servo loop which receives motor speed feedback signals from a variable reluctance pick-up 46 whi~h, as shown in Figure 3, comprises a fixed sensor 47 and a toothed wheel 48 mounted at the bottom of the motor shaft 23.

The data input connector 19 is connected to a receiver/decoder, for instance complying with the RSZ32 or RS432 standard. The output of the receiver 49 is connected to a sequence control logic circuit 50 which receives timing signals from a timer 51 controlled by a crystal oscillator 52. The sequence con~rol logic circuit 50 has an output conn~cted to a data transmitter 53 which sends data via the rotary transformer 30, 31 to the carousel 7. The sequence control logic circuit 50 is also conn~cted to a removable da~a module 54 which compris~ a sequence ran~om access memory 55, a page store r~ndom access memory 56, and a rechargeable battery 57 ~or m~intaining the contents of the memories 55 and 56 when the display is disconnected from the mains.

The ~arousel 7 comprises a da~a receiver 58 which receives data from the rotary transformer 30, 31 and which has outpu~s connected to a pag0 control circuit 59, a timing ~raln and control logic circuit 60, and display data random access memory 61. The logic circuit ~0 is connec~2d to outputs of the page ~on~rol circuit 59 and the memory 61, and receives clock pulses from a crystal ~ ~/12354 PCT/GB90/~K~
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oscillator 62. The logic circuit 60 and the memory 61 are connected to the display cards 5 by the buses 36 and 37 shown in Figure 4.

The display operates as follows. When ~he display is first actua~ed by supplying mains power to the input co~nector 43, the motor 12 rotates the carousel 7 and accelerates until a preselected speed of rotation is reached. The mo~or speed control circui~ 4S then stabilises the ro~ary speed of the carousel at ~he preselected value. The speed is not actively synchronised in any way with the display electronics in the carousel 7, but speed stability is based on the stability of ~ crystal oscillator which is substantially identical to the crystal oscillator 62 which controls display timing. The crystal oscillator for the motor speed control circuit 45 may be provided by the crystal oscillator 42 or may be provided i~depe~dently.

Meanwhile, display data are sent from the data module 54 by the sequenc~ co~trol logic circuit 50 via the data transmitter 53 and the rotary transformer 30, 31 to the carousel 7, whose elec~ronics receive power via the slip rings 24, 26 from the power supply unit 44. Display and con rol data are received by the data receiver 5~ and are stored in the display data memory 61. The timing chain and control logic 60 then cause data to be supplied .rom the me~ory 61 to the display cards 5 with appropriate timings ~o provide the desired displayed image.

Th~ cylindrical display surf ce swept by the columns- of light emitting diode~ 6 is divided into 512 circum~erential by 64 vertical pixels and the memory ~
contains data ~or providing four comple~e displays, each using all of the pixels and referred to hereinafter as a "page". At any one time, one of the pages is hidden or blanked and does not affect the display but instead is , .

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available to receive fresh display data from the base unit B~ The other three pages provide three display images which are superimposed so as to provide ~ complete image or "band".

The data for each pixel may control it such that it is off, green, rad, or yellow (green and red). Data held in the page control circuit 59 allows each of the pages to commence at a selectable circumferential position.

The display timing is ~etermined by the crystal oscillator ~2 and a static image relies on substantially identical timing control within the motor speed control circuit 45. However, a rotating image may b obtained by selecting a variation in speed by means of the motor speed control circuit 45 or by periodically altering the circumferential starting po~ition of one or more of the displayed pages. A degree of animation may also be achieved by loading f resh pages from the data module 54 into the display data memory 61 at a speed sufficient to provide an apparently changing image, or by displaying only one of the four pages stored in the memory 61 at a time and in sequence.

In a preferred embodiment, the circumferential starting position for each page can be selected as any one of 256 cirsum~erent~al co}umns of pixels. The starting point thus has hal~ th~ circumferential resolution of the display, but this has been found adequate in practice while relievin~ design and ~echnical requirements on the elec~ronics of the display.

Figure 7 i~ a circuit diagra~ of one of the display cards 5. The card is implemented with high-speed TTL and CMOS
integrated circu~ts of the 7400 series, available from various manufacturers, and the type numbers for the individual integrated ~ircui~s will be given hereinafter.

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For the sake of clarity, multi-line connections or buses are shown in the circuit diagrams as a single line with a short crossing line and associated number indicating the number of lines or channPls making up the connection.

The thirty two light emitting diodes 6 are arranged as four groups of eight, with each group being controlled by a respective octal latch/driver 63 to 66 of the type 74LS374. The latch/drivers have latch enable inputs which are connected toge~her and to a display card input 67 for receiving an upda~e conkrol signal UD. Each o~tal latch/driver comprises eight identical latches, each of which is controlled by the enable input and i5 capable of supplying sufficient current to drive the corresponding light emitting diode 6.

The data inputs to each latch/driver 63 to 66 are connected to the outputs of set/rese~ flip/~lops 68 to 75, each of which comprises a quad set~reset flip/flop of type 74LS279. The flip/flops 6~ to 75 have clear inputs which are connected to a display board input 76 for receiving a clear signal CLR.

The set input~ of the flip~flops 68 to 75 are connected to the outputs of four octal buffer tri-state line driv~rs 77 to 80 of type No.74~G244, whose data inputs are connected in parallel to a common 8-line bus for receiving display data signals D0 to D7. The oc~al bu~ers 77 to 80 have enable input~ connected ~o the outputs of AND gates 81 to 8~, respectively. The AND
gates 81 to 84 have first inputs connected to receive st~obe signals S0 ~o S3, respectively, and second inputs conneote~ toge~her to receive a board enable signal 3E.

The input si~nals UD, CLRt BE, S0 tO S3, and D0 to D7 are rec~ived from the ~us 36 or 37, depending on whether ~he , 7 ~/1~ ~ PCT~GB~/~

particular card 5 is a member of the group "1" to "8" ~r "9" to "16". In addition, a supply line Vcc and a common line (not shown) are connected to the respe~ti~e bus, which provides power to the display card 5.

In order to write new data ~or controlling the llght emitting diodes 6 to each display card 5, a board enable signal ~E is supplied to the selected card. The gates 81 to 84 are there~ore opened and the board i ready to ; receive the strobe signals S0 to S3. Data D0 to D? are supplied to the octal buffers 77 to 80 for controlling the light emitting diodes connected to the octal latch 63. The strobe signal S0 is supplied so as to enter the data in the octal buffer 77, and hence into the flip/flops 68 and 69.

Data for the next group of eight light emittlng diodes is then supplied on the bus as bits D0 to D7 and the strobe signal S1 is supplied so as to enable the octal buffer 78 and enter ~he da~a in the flip f}ops 70 and 71. This process is repeated until the data for one column of ~: ~ pix ls for one of the three pages to be displayed has b~en antered in the flip/flop3 6~ to 75. The whole process i5 then repeated for the same colu~n of pixels or the second page to be displayed, without clearing the flip flops 6~ to 75. The new data is therefore ~e~f~ctively superi~posed on the data ~or th~ previous page . The process is then repeated again f or ~he ~hird page, aft~r which the board enable signal }3E is removed.
;: ~ : : : :
:Thi~ proces3 is repeated for each of boards "1" to "8"
a~d simultaneously or boards "9" to "16" via the two data buse6 36 and 37 so that ~he data for displaying the next six~een columns of pixels ara enterPd in the flip/flops of all sixt~en display boaxds. At the end of ~ ~54 P~T/GBgO/~
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this cycle, the update signal UD is supplied to all sixteen boards so tha~ the new data axe written into the latches 63 to 66 simultaneously on all boards and the sixteen next circumferential columns of pixels ar~
displayed in place of the previous on~s. A clear signal CLR is then supplied to all sixteen boards so as to reset all of the flip/flops 68 to 75 in readiness for r~ceipt of the data for the next columns of pixels.

The data receiver 58, the page control circuit 59, the timing chain and control logic circuit 60, the display data random access memory 61, and the crystal oscillator 62 are shown in more detail in figure ~.

The carousel 7 has a local power supply unit 85 which receives power from the slip rings 24, 26 and supplies power to the electronics shown in figure 8 and to all of the display boards 5.

The rotary transformer 30, 31 is connected to a frequency shift keying (FSX) demodulator 86 whose output is conn~cted to a decode logic circuit 87. The logic circuit 87 has an ou~put connected to a data input of th~
memory 61, and further outputs whose connections will be described h~reinafter.

Th~ crystal o~cillator 62 supplies clock pulse~ to a 16 bit binary cou~ter 88 whose leaæt significant bit outputs are shown at the left with the slgnificanc~ of the bi~
outputs increasing progressively to the right. Thus, the two least significant bi outpu~ are oonnected to inputs of a 16 bit 2-to-1 multipl~xer 89 a~d fo th inputs of a decoder 90 whi~h decodes ~he.two bits to 1-of-4 outputs which provida the strobe signals S0 ~o S3 for the display boards. The next two co~nter ou~puts pro~ide a two bit ''~ ~/1~3~ PCT/GBgO/M~

code to the multiplexer 89 and indicate which of the four pages making up a band is currently being addressed.
These outputs are also connected to a decode logic circuit 9l and to a 4 by 8 bit position random access memory 92 and a 4 by ~ bi~ colour random acc~ss memory 93. The next three outputs of the counter 8~ are supplied to a four bit adder 94 and to a decode logic circuit 95. The three bits at these outputs indicate the display boards of the first and s~cond groups which are currently b~ing addressed, and the decode logic circuit 95 decodes these bi~s and signals from t~e decode logic circuit 9l so as to provide l-of-8 outputs constituting eight board enable signals ~E together with the clear signal CLR and the update signal UD. The decode logic circuit 9l supplies a signal to the deoode logic circuit 95 indicating the currently selected blank page so as to prevent da~a from being written to the display boards.

The mos significant nine outputs of the counter 88 are used to ~elect the sixteen columns of pixels ~o be written to the sixteen display cards. The least significa~t of these nine ou~puts is connected direct to the multiplexer 89 whereas the r~maining eight outputs are connected to an 8 bit addar 96 which is also connected to the 8 bit output of the position memory 92.
Tha positio.n offset for the currently selected pag~ is : thus added to the eigh~ most significant bi~s and the sum is supplied to the mul iplexer 89. In order to sypchronise the data correctly, the four most significan~
bits of th~ sum from the adder 86 are supplied to the adder 94, whose least significant three bit outputs are connected to the mul~iplexer 89 and whose most signiflcant bit output controls a data bus driver 97 direct and a data bus driver 98 via an inverter 99. The outputs of the drivers 97 an~ ~8 are connected to the WO 90tl2354 PCr/GB9OtO0564 C~
buse~ 36 and 3,. respective~y, whereas the inputs of the drivers 97 and 98 are connected in parallel to the data outputs of the page data memory 61, which is a 16k by bit memory.

The decoder logic circuit 91 has an output signal connected to th~ control input of the multiplexer 89, whose outpu~s are connected to the address inputs of the memory 61. A 16 bit load address counter 100 has its outputs connected to th~ other inputs of the multiple;~r 89 and has an increment input 101 and a reset input 1 ~
connected to the decode logic circuit 87. The m~mories 92 and 93 have data inputs connected to outputs of the decode logic circuit 87. A page load circuit 103 has a two bit output con~ected to the memories 92 and 93 and has a two bit input connected to the decod~ logic circuit 87 .

At any one time, one o the four pages whose display data are held in the memory 61 is desig~ated by the base unit as a blank page which is not to be di~played so that data for this page may be written to the memory 61 Whenever the third and fourth ou~puts of the counter 88 selec~
this phge, which may be changed as desired in the base unit, th~ page load circuit 103 makes the memories 92 an~
93 ready t~ receive new page position and colour data wherea~ the decode logic 91 blanks the display and switches the multiplexer so as to receive an address f rom the load address cou~ter 100. The data supplied in FSR
form via the ro~ary transformer 30, 31 has a relatively slow bit rate which is much slower than the rate at which da~a are transferred from the memory 61 ~o the display boards 5. Howaver, this does not mat~cer as it is not required to update the memory 61 at such a f ast rate.
Incr~men~ and rese~ control signals to the load address WO ~/123~
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counter 100 allow data supplied to the data input of ~he memory 61 to be written to the correct location irrespective of the state o~ the outputs of the~ counter 88.

When the two bit pag~ output of th~ counter selects th next page, th~ decode logic circuit 91 switches the multiplexer 89 so that the counter 100 is disconnected from the address inputs of the memory 61 and the other multiplexer inputs address the memory. Further, the memori~s 92 and 93 are retur~ed to the read mod~, the data input to the memory 61 is disabled, and the d~code logic circuit 95 begi~s supplying board enable signals BE
for writing to the display boards.

The colour memory 93 contains a two bit code defining the colour for ~ach of the four pages for which display data are cllrr~ntly stored in the memory 61. The four states of these two bits represent bla~k, red, green and yellow (red and green). These da~a are decoded in the decode logic circuit 95, together with the currently selected display board, to ensure that the appropriate data are written to board, which contains only red or o~ly green light emitting diodes. The control circuit shown in figure 8 thus applies, for each of the three pages which are currently to be displayed, the display data for controlling each of the four groups of light emitting diodes in turn for each of ~he three pages in turn for each of the two display boards co~nected to the buses 36 and 37 i~ turn for each se~ of sixteen columns of picture elements in turn which are to be displayed nex~ by ~he display boards, ~ycling through the comple~e se~ of circumferential columns in sixteen such cycles.

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WO90/1~54 PCT/GB90/~4 2 ~ 9 ~

The remova~le d~ta module 55 cantains data relating to~
many pages and ~ands to be displayed and the sequence memory 55 defines the sequence in which page data from the memory 56 are selected by the sequence cont~-.l logic circuit 50 for transmission to the carousel. The timing of transmis~ion of new page data to the carousel is con~rolled by the timer S1. The module 54 may be replaced by other modules defining different display ~eque~ces in order to adapt the display for a desired application. New data may also be supp .~d via the input port 19 "on line" from, for instance, a .~dem connectad to a remote computer or a portable computer connected to the input port 1~.

Display data supplied from any suitable source to the inputr port 19 may be usad to reprogramme the memories 55 and 56 with the new data, and may even be used to write new data direc~ly to the memory 61. These ~unctions are controlled by the sequence control logic circuit 50.
Thus, it is possible to enter new data without changiny the removable data module SS. If desirable, the input por~ 19 could be perman~ntly connected to a source of displ~y data, thus permanen~ly augmenting or replacing the function of the module 54.

The motor speed con~rol circui~ 45 is shown in more detxll in Figure 9. The mo~or 12, whtch is an ~C
induc~ion mo~or, i3 conn~cted in series with a ballast r~istor 10~ be~ween Live and Neutral lines connected to the mains input connector 43. A solid state relay lOS
based on a triac is connec~ed in parallel with the balla~t re~istor 104 and has a control input connec~ed to the output of a flip/flop 106.

~go/l23~ PCT/GB~/~4 19 2~8~
The flip/flop has a reset input connected to the outpu~
of a pulse generator 107 which has an input connected to receive the 50 or 60 ~æ AC mains input and which is ~rranged to produce an output pulse at a predetermined time delay af~er each zero crossing of the mains supply.
The output o~ the pulse generator 107 is connected to a load input of a counter 108 so as to preset the counter to a preset value selectably determined by a plurality of switches 109 connected to count~r pr2set inputs for selecting the desired speed of rota ion of the motor 12.
The counter 10~ h~s an output which is activated when the counter reaches the zero state, this output being connected to a set input of ~he flip/flop 106.

The counter 108 has a count-down clock input connected to the output of an AND gate 110 having a first input which receives clock pulses from a crystal oscillator and frequency divider 111 and a second input connected to the output of a frame pulse generator 112. The input of the generator 112 is connected to the output of a pulse shaper circuit 113 whose input is connected to the sensor 47 which, together with the toothed disc 48, forms the motor speed pick-up transducer 46. The pulse shaper 113 shapes the output signal of the transducer and the frame pulse generator 112 converts this into a frame pulse whose duration i8 inversely propor~io~al to the rotary speed of the motor sha~t 23.

During each half cycle of the mains current, the pulse generator 107 resets the flip/~lop 106 ~nd pxesets the counter 108 to the preset value defined by the switches 109. The frame pulse generator 112 opens ~he gate 110 to pass the clock pulses from the crystal oscillator and divider 111 so as to decremen~ the counter 108 until the end of ~he frame pulse. If the speed of rotation of the wo ~/123~ PCT/GB90/~

2~
motor is ~oo slow, the frame pulse i5 long enough to ^
allow the counter 108 t~ be decrement~d to zero so that the counter sets the flip/flop 106. The flip~lop 106 thus actuates the solid tate relay 105 which i~ turn sho~ts out the ballast r~istor 104. The motor power is therefore increas~d and the motor accelerates. The next pulse from the pulse generator 107 resets the flipJflop, thus deactivating the relay 105 so that the power to the motor 12 is reduced by the ballast resistor 104.

When the motor spaed exceeds the preset value, the frame pulse generated by the generator 112 is too short to allow the counter 108 to be decremented to zero between consecutive pulses from the generator 107. The flip/flop is therefore not ~et and the solid state relay 105 remains off so that the ballast resistor 104 is not shorted. The r~duced power to the motor 12 thus allows the motor to decelerate until the frame pulse is again long enough for the counter 10~ to be decremented to zero.

This motor speed control circuit providss Yexy f ine control of speed and, by appropriate selection of parameters, such a~ the value of the ballast resistor 104, th~ ~ze of the counter 108 and the output frequency of the oscillator and divider 111, the a~tual motor variation once the desired speed has been achièved is very small and imperceptible to a viPwer of the display.

The display may be used in a varie~y- of applica~cions, such as displaying information or adver~ising material in shop windows . The light output is ~;u~f ici~ntly high f or the display to be elearly visible in direct sunlight, and the display provides an attractive and eye-catching image. The images to be displayed c:an be changed in a ~0 ~/1~ ~ PCT/GB~O/~

preprogrammed sequence and new sets o~ images can easi~ly be programmed in~o the display by changing the removable data module 54 or by supplylng data through the input port 19 and thus not requiring any hardware changes. New data may be supplied by a portable computer temporarily connected to the input port 19. Alternatively, new data may be supplied to the input port 19 from a modem connected to a telephone line. The display can be made in a variety of si2es and may be permanently fixed at a site or may be sufficiently compact to be tran~portable.
The images provided by the display may even ~e changed sufficiently quickly to provide a degree of image movement or animation. Images may be stationary on the cylindrical display area or may rotate, for instance by varying the motor speed under software control in addition to or in place of the speed selection switches 109 or by varying the page positions by periodically writing new positions to the memory 92 from the base unit.

Although the embodiment described uses 16 interlaced columns o~ light emit~ing diodes and is restricted to green and red light emitting diodes with a vertical resolut~on of 64 pixels and a circumferential resolution of 512 pixels with each pixel being capable of being displayed as black, red, green, or yellow, this is purely by way of example and any o~her suitable values for these di~play parameters could be chosen. Thus, a different number of columns could be used, different vertical and circumferential resolu ions could be pro~ided, light emi~ting diodes or other light emit~ing devices of different and/or additional colours could be employed, and the intensity of each picture element colour could be controlled so as to have additional intermediate intensities between off and full-on.

Claims (14)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A display comprising a static unit and a moving unit, the moving unit carrying a plurality of light sources and being arranged to move relative to the static unit so that the light sources perform a repeated movement, the moving unit including a memory for storing data for providing a plurality of displayed images and control means for controlling the light sources so as to display at least one selected image at a time.

2. A display as claimed in Claim 1, in which the moving unit is a rotating unit and the light sources are arranged as a plurality of columns parallel to the axis of rotation.

3. A display as claimed in Claim 1, in which the light sources are light emitting diodes.

4. A display as claimed in Claim 1, in which the static unit is arranged to communicate with the moving unit by means of a communication link.

5. A display as claimed in Claim 4, in which the communication unit is a rotary transformer.

6. A display as claimed in Claim 4, in which the static unit contains a further memory for storing data for a plurality of further displayed images and transmission means for transmitting the data from the further memory to the memory and the control means of the moving unit via the communication link.

?90/12354

7. A display as claimed in Claim 2, in which the light sources of each column are oriented parallel to each other at an angle to a radius from the axis of rotation through the column, the light sources of at least two of the columns being oriented at respective different angles.

8. A display as claimed in Claim 2, in which at least two of the columns axe offset relative to each other parallel to the rotational axis.

9. A display as claimed in Claim 1, in which the moving unit is a rotating unit, the display further comprising a motor for driving the rotating unit and a control circuit for controlling the speed of the motor, the control circuit comprising means for repeatedly presetting a counter to a preset value, means for stepping the counter towards a predetermined value at a predetermined rate for a period related to the period of rotation of the motor, and means for supplying increased power to the motor when the counter reaches the predetermined value.

10. A display comprising a static unit and a rotating unit, the rotating unit carrying a plurality of columns of light sources arranged to sweep a common cylindrical surface, the light sources of each column being oriented parallel to each other at an angle to a radius from the axis of rotation through the column, and the light sources of at least two of the columns being oriented at respective different angles.

11. A display as claimed in Claim 10, in which at least two of the columns are offset relative to each other parallel to the rotational axis so as to provide interlacing.

??90/12354

12. A display as claimed in Claim 10, in which the light sources are light emitting diodes.

13. A display comprising a static unit, a rotating unit carrying a plurality of light sources, a motor for driving the rotating unit, and a control circuit for controlling the speed of the motor, the control circuit comprising means for repeatedly presetting a counter to a preset value, means for stepping the counter towards a predetermined value at a predetermined rate for a period related to the period of rotation of the motor, and means for supplying increased power to the motor when the counter reaches the predetermined value.

14. A motor speed controller comprising means for repeatedly presetting a counter to a preset value, means for stepping the counter towards a predetermined value at a predetermined rate for a period related to the motor rotation period, and means for supplying increased motor power when the counter reaches the predetermined value.