e001026.pdf

GENERAL INTEREST

Rhine Tower clock Mk II

a special design, with a circuit

board shaped like the tower

The DCF-controlled

LED clock design,

published in the May

1998 issue of Elektor

Electronics, is a

radio-controlled elec-

tronic version of the

clock mounted on the

Rhine Tower in Düs-

seldorf. Inspired by

the many positive

reactions to this pro-

ject, its designer has

reworked the soft-

ware to add new fea-

tures. To make things

even nicer, Elektor

Electronics has

designed a special

circuit board in the

shape of the actual

tower in Düsseldorf.

Design by D. de Mülder

Building a circuit yourself is even more

pleasant when the result is something

unique. Those of you that have built

the original DCF-controlled LED clock

will certainly have experienced this

first-hand. Anyone who sees such a

clock for the first time will undoubt-

edly wonder what it is and how it

works.

The clock that is integrated into

Düsseldorf ’s Rhine Tower consists of a

series of lights arranged in a vertical

line. The 39 lamps that are used to indi-

cate the time on the tower are replaced

in this project by yellow LEDs. The out-

line of the Rhine Tower can be seen in

the drawing of Figure 1 . The nine LEDs

at the very bottom display units of sec-

onds (0 through 9). The four LEDs

above them display tens of seconds.

The minutes and hours are encoded in

a similar manner. Finally, there are two

Elektor Electronics

1/2000

LEDs that display tens of hours. All of

this can be clearly seen from the draw-

ing. At 23:59:59 all lamps are illumi-

nated, and at exactly midnight

(00:00:00) all lamps are out. A new 24-

hour cycle starts at this point.

In contrast to the previously pub-

lished design, the beacon lights are also

included in the present design. In

addition to the four lamps that indicate

the wind direction (N, E, S and W),

there is also a beacon lamp at the top

of the tower. The result is a faithful

reproduction of the Rhine Tower

(clock).

In addition to these cosmetic modi-

fications, a number of new functions

have been added in the software. It is

thus no longer necessary to use a DCF

receiver (although this simplifies oper-

ation and gives better results). The new

clock can function without the radio

time reference signal, although it will

naturally not be as accurate over an

extended period of time.

Since the DCF receiver is no longer

essential, a number of pushbuttons

have been added to allow the clock to

be set.

An additional new function is the

extraction of the day of the week from

the DCF signal. It can also be manually

entered using the pushbuttons. With

this additional information, it is possi-

ble to use the clock as an alarm that

takes the day of the week into account.

Naturally, an electronic buzzer is also

included to generate the wake-up sig-

nal.

In order to accommodate all these

functions, it is of course necessary to

use a somewhat bigger processor. This

is the price that must be paid for the

extra features.

be omitted (along with R7, which is

connected to JP1).

It goes almost without saying that,

while the hardware is almost the same

as in the earlier design, the controller

software has been extensively modi-

fied. In order to use the new functions,

it is thus necessary to acquire a new

controller. It is possible to use the new

circuit board with the old controller, if

you wish, but the additional LEDs will

not function in that case.

C ONSTRUCTION

The printed circuit board track layout

and component layout are shown in

Figure 3 . As is immediately apparent,

this is no ordinary circuit board. Not

only does it have an unusual form, its

size is also special, which is why the

illustration is only 55% of the actual

size. If you want to etch your own cir-

cuit board, you must first enlarge the

layout drawing by 182%. Alternatively,

you can find the full-scale layout draw-

ing as a PDF document at Elektor ’s

Internet site (http://www.elektor-elec-

tronics.co.uk). Of course, none of this

matters if you buy the circuit board

ready made. In addition, the ready-

made circuit board is milled to the

shape of the Rhine Tower by the board

manufacturer, saving you the trouble

of doing this yourself. If you make

your own circuit board, a bit of exercise

with a coping saw will be necessary to

give the board its proper shape.

If you wish, you can colour the

board by applying a thin coat of spray

paint to the component side of the cir-

cuit, board before fitting the compo-

nents (but take care to avoid clogging

the holes!).

The foot of the tower consists of two

circuit board sections that can be sepa-

rated from the rest of the board if

desired. The bottom-most section

accommodatees the pushbuttons,

while the middle section holds the

processor that drives the whole circuit.

It is a question of taste whether to leave

everything in one piece or divide it

into two or three separate boards. It’s

up to you to decide, and the choice will

depend in part on how the finished

unit will be set up.

Since the three portions of the

printed circuit board are electrically

separate, a number of interconnections

must be made, regardless of the final

configuration. You should first fit the

wire jumpers and all necessary pins.

It’s a good idea to used sockets for IC1

and IC2. When fitting the LEDs, pay

good attention to the polarization.

With so many LEDs, it’s easy to make

a mistake.

After all the components have been

fitted, the three portions of the circuit

board must be connected to each other

using a number of bits of wire and a

piece of flatcable, even if they are not

restaurant lighting

hours: tens

hours

tower lights (red)

minutes: tens

minutes

tower lights (red)

seconds: tens

C ONTROLLING LAMPS

WITH BITS AND BYTES

The schematic diagram of the LED

clock is shown in Figure 2 . A large part

of this is the same as the schematic of

the 1998 design. The same type of

microcontroller is still used, as well as

the same LED-driver IC and power

supply. These parts of the circuit are all

straightforward. The driver for the

piezo buzzer is new. With the specified

components, any buzzer that works

with a 5 V supply voltage and a cur-

rent not exceeding 50 mA can be used

for Bz1. The three pushbutton switches

are connected to processor inputs that

were not used in the previous design.

The extra LEDs fit into previously

unused positions in the matrix.

As before, an additional LED that

lights whenever the supply voltage is

present can be connected via jumper

JP1. Resistors R4 and R5 are provided

to allow experiments with other dis-

plays to be carried out. Under normal

circumstances, these resistors are not

necessary, and in most cases they may

seconds

980035 - 11

Figure 1. This drawing shows

the configuration of the clock on

the Rhine Tower in Düsseldorf,

Germany.

Elektor Electronics

1/2000

100n

4µ7

63V

SEGA

SEGB

SEGC

SEGD

SEGE

SEGF

SEGG

SEGA

RST

P10/IN+

P11/IN–

ID0

ID1

ID2

ID3

ID4

ID5

ID6

ID7

SEGC

IC1

SEGG

INT0/P32

INT1/P33

P12

P13

P14

P15

P16

P17

IC2

SEGE

SEGD

T0/P34

T1/P35

SEGB

SEGF

7218A

89C2051

DIG3

DIG1

DIG2

DIG3

DIG4

DIG5

DIG6

DIG7

DIG8

DIG1

RXD/P30

TXD/P31

DIG6

P37

MODE

DIG2

DIG7

DIG5

DIG4

DIG8

12MHz

100n

47p

4...22p

IC3

D49

1N4001

7 805

D4 1

D3 9

D 30

D 25

D 16

D11

D 2

JP1

D4 2

D4 0

D 31

D 26

D 17

D12

D 3

1000µ

25V

10µ

63V

D4 3

D5 1

D 32

D 27

D 18

D13

D 4

D4 4

D5 2

D 33

D 28

D 19

D14

D 5

ALARM

STOP

DCF

PULSE

ON/OFF

(D50)

SEGA

(D56)

(D1)

SEGC

D4 5

D5 3

D 34

D 29

D 20

D15

D 6

SEGG

SEGE

SEGD

D4 6

D5 4

D 35

D 21

D 7

SEGB

D50

SEGF

D 1

DIG3

D4 7

D5 5

D 36

D 22

D 8

DIG1

R10

4k7

DIG6

DIG2

D4 8

D 37

D 23

D 9

BC557B

DIG7

DIG5

Bz1

DIG4

DIG8

D 38

D 24

D1 0

D 56

990076 - 11

separated. Connect corresponding

points to each other (A to A’, B to B’

and so on, finishing with K to K’). After

this, connect a length of 20-lead flatca-

ble between K1 and K2. The optional

DCF receiver can be connected to PC1,

PC2 and PC3. The CPU generates

interference that can affect the opera-

tion of the DCF receiver, so the receiver

should be located 20 to 30 cm away

from the CPU. Use a piece of screened

cable for the connection.

A wall adapter that can deliver

around 250 mA at a d.c. voltage

between 8 and 12 V can be used to

supply power to the

circuit.

Once all intercon-

nections have been

made and all compo-

nents installed, the

mains adapter can be plugged in. If a

DCF module is used and the signal

reception is adequate, LED D50 should

flash once per second. This is also true

for some of the beacon lamps. If signal

reception is good (as indicated by D50

flashing), the exact time should be dis-

played after two to three minutes.

DCF77 reception should be possible

Figure 2. The schematic dia-

gram of the clock. The simi-

larity to the original DCF-

controlled LED clock circuit

is readily apparent.

within a radius of

1500 km (just

under 1000 miles)

from the transmit-

ter location in

Mainflingen, Ger-

many. From previous projects employ-

ing the DCF77 signal we know that

reception is just about adequate in

South-Eastern parts of England, South

Scandinavia and most of Central

Europe. If you live in a fringe area,

remember that the radio signal is not

required all the time! Also remember

that DCF77 transmits CET (Central

Elektor Electronics

1/2000

D51

R10

D55

D54

D53

D52

D47

D48

D46

D40

D39

D38

D37

D36

D35

D34

D33

D32

D31

D30

D45

D29

D28

D27

D26

D25

D24

Figure 3. This may not be the

largest circuit board ever

offered by Elektor Readers’

Services, but it is certainly one

of the most attractive.

Artwork shown at

55% of actual size.

D23

D22

D21

D20

D19

D18

D17

D16

D43

D41

D42

European Time).

None the less, if you do not use a

DCF module, you will have to set the

time manually and initialize the non-

DCF operating mode. To do this, press

S3 at the same time as power is

applied. The restaurant lamps will

come on, while all other lamps will

remain off. Release S3 and start with

setting the time. Use S1 to set the hour.

The hours count is increased by one

each time S1 is pressed. After this, use

S2 to set the minutes. Note that there is

an automatic ‘rollover ’ from the min-

utes setting to the hours setting.

Use S3 to set the day of the week. It

has a double function in this regard.

Press it briefly (0.1 to 1 second) to set

the day of the week; the count

increases by one each time the button

is pressed. While the day of the week

is being set, the first seconds LED indi-

cates Monday, the second LED Tues-

day and so on. After Sunday (all seven

LEDs on), the day automatically

D15

D14

D13

D12

D11

D10

990076-1

IC2

IC1

Elektor Electronics

1/2000

pressed — either briefly

(up to 0.6 second) or

longer (more than 0.6 sec-

ond). The alarm time is

specified in hours and

minutes. The functions of

the switches are as follows:

COMPONENTS LIST

Resistors:

R1,R2 = 47k Ω

R3=220 Ω

R4,R5,R7 = see text

R6 =10k Ω

R8 = 1k Ω 8

R9 = 1k Ω

R10 = 4k Ω 7

S1 short: increment the

hour

S2 short: increment the

minute

S3 short: increment the

weekday

S1 long: switch the

alarm on or off

S2 long: program the

weekday

S3 long: return to the

time display

Capacitors:

C1 = 4 µ F7 63V radial

C2 = 4-22 pF trimmer

C3,C4 = 47pF

C5,C6,C7 = 100nF

C8 = 1000 µ F 25V

C9 = 10

F 25V radial

Semiconductors:

D1,D46,D47,D48 = LED, high eff.,

green

D2-D40,D56 = LED, high eff., yellow

D41-D45,D50-D55 = LED, high eff.,

red

D49 = 1N4001

T1 = BC557B

IC1 = AT89C2051-12PC (order code

996519-1 )

IC2 = ICM7218 A IJI

IC3 = 7805

Figure 4. The assem-

bled prototype of the

clock.

Each time S1 is pressed,

the alarm time in increased

by one hour. S2 sets the

minute of the alarm time

in a similar manner, and S3

the day to which the alarm

time applies. The first time S3 is

pressed, the LED belonging to Mon-

day starts to flash. If the alarm should

only be active on this day, press S2

until the flashing weekday lamp stays

on continuously. To program more

than one day in the week, use S3 to

increment the weekday count and

then S2 to select the day. If the week-

day count rolls over from Sunday to

Monday, all daily programming is

erased and you will have to start over

with selecting the day(s).

The last position of the cursor is

saved when the clock is returned to the

time display mode. This makes it pos-

sible to add other days to the program

at some later time. Finally, press and

hold S1 to activate the alarm function.

The lamp built into S1 will illuminate.

To terminate the alarm setup proce-

dure and return to the normal time

display, press and hold S3. When the

alarm goes off, you can silence it by

pressing S3.

The alarm output itself is a logic-

level output that is connected to a

Miscellaneous:

JP1 = 2-way jumper

K1,K2 = 20-way boxheader

Two 20-way sockets and a piece of

flatcable

S1,S2,S3 = pushbutton ,type

‘Digitast’ with integral LED (ITT

Schadow)

X1 = 12 MHz quartz crystal

Bz1 = dc buzzer, 5 or 6 V

Heatsink for IC3 (15 K/W, e.g., ICK35)

PCB, order code 990076-1

Optional: DCF-module (Conrad

Electronics order code 64 11 38-55)

returns to Monday (one LED on).

After everything has been set, you

can start the clock using S3. If S3 is held

pressed for longer than one second,

the clock will start, and it starts exactly

on the minute. You should therefore

press S3 at the 59th second of the

minute, so that the clock will start

exactly when the minute changes.

After a bit of practice, you should find

the operation of the clock very simple.

Those of you that use a DCF module

need not be concerned about all this,

since clock synchronization is fully

automatic with a DCF module!

switching transistor and a d.c. beeper.

If desired, a sound-effects generator, a

relay or some other type of circuit

could be connected to this output. In

some cases it may be necessary to con-

nect a buffer to the output. There are

lots of ways you can experiment with

this unusual clock.

S ETTING THE ALARM

After the clock is set and is running, the

alarm time can be set. The clock con-

tinues to run in the background while

the alarm is being set. However, the

DCF module is temporarily not used as

long as the alarm is being set. This is

not a problem, since the clock is crys-

tal-controlled and thus runs quite accu-

rately using its own internal timing.

(Note that many battery-operated DCF

clocks synchronize themselves with

the DCF time only once per day, in

order to save energy. This is usually

sufficient to maintain the desired level

of accuracy.)

To set the alarm time, first press S3.

Either all LEDs will go out, or they will

indicate the last-entered setting for the

alarm time (including the day of the

week).

All three pushbuttons have double

functions for setting the alarm time,

depending on how long they are

(990076-1)

Text (Dutch original): H. Steeman

Design editing: K. Walraven

The Rhine Tower clock

on the Internet

If you are interested in the Rhine Tower and its clock you may find a lot of inter-

esting information on the Internet. For example, a Windows screensaver based

on the Rhine Tower can be found at http://www.duesseldorf.de/tourist/down-

load/index.html.

A site that is based on the theme of clocks can be found at

http://www.hsp.de/~wiegels/programm/uhren.htm. Naturally, software that emu-

lates the Rhine Tower clock is available at this site.

If you want to know more about the Rhine Tower itself, the site ‘Höhe Türme’

(‘high towers’) is certainly something for you. Go to

http://www.hsp.de/~wiegels/tuerme/hoch.htm to see all the information that is

available regarding this high tower (and others).

Elektor Electronics

1/2000

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