e00b016.pdf

GENERAL INTEREST

An Electronic Bell

a novel decoration not just for Christmas time

Design by D. Petig

With Christmas not far

away this project is guar-

anteed to add a sparkle to

the festivities.

Circuit description

The circuit diagram shown in Fig-

ure 1 can be divided into two parts.

The simplest part consists of 48

green LEDs forming the outline of

the bell. The 150 Ω series resistors

have been calculated assuming a

forward conduction voltage drop of

about 1.9 V for each LED so it is

important here not to use high effi-

ciency types.

The rest of the circuit is used to

control the clapper display and

chime generator. 16 red LEDs are

used to simulate the bell clapper by a

moving light point (again high effi-

ciency types are unsuitable here).

IC3a/b together with R1 and timing

components R2 and C2 form an oscil-

lator that controls the speed of the

clapper. The output of this oscillator

is used to clock a binary up/down

counter IC4. This counter has four

outputs and therefore counts up from

0 - 15 or down from 15 - 0 depending

on the logic state of its up/down

input. The outputs of this counter are

connected to the inputs of the

decoder IC2. This chip will set high

only one of its 16 outputs corre-

sponding to the binary code at its

four inputs. Each of these 16 outputs

is connected to an LED. The outputs

representing each end of the binary

count (pin 11 and pin 15 of IC2) are

also used to toggle a ﬂip-ﬂop formed

from IC3c/d. This has the effect of

switching the counter to count down

when it reaches its maximum count

and to count up when it reaches its

minimum count.

The overall effect is that the red

light point swings continually back-

wards and forwards between D1

and D16.

The gong with eight legs

The two trigger signals from IC2 are

also connected to an OR gate formed

by diodes D65 and D66. The output

of the OR gate is connected to the

trigger input of IC1. This component

is the SAE800 gong IC manufactured

by Infineon. ( Figure 2 ). This IC pro-

duces a single, dual or triple tone

sound envelope from a single trigger

signal and can directly drive a small

loudspeaker or piezo sounder. The

frequency of the tone is set by the

values of C3 and R6 and the output

volume by R7. The internal logic not

only controls sequencing of the

tones in the sound envelope but also

the volume of each tone and its sus-

tain time. Altogether each gong

sound lasts for approximately 7 s.

This chip has many interesting fea-

tures and a copy of the datasheet is

available for download from the Inﬁ-

neon website at: http://www.infi-

neon.com .

In our application the IC is oper-

ated in its single tone mode, the

intention here is to imitate the deli-

cate chime of a glass hand bell and

not the deep sonorous clang of Big

Ben. The operating frequency is

given as f 0 = 0.03125/(R6/C3) =

4300 Hz. This is relatively high and a

piezo sounder is well suited to repro-

ducing this frequency.

Circuit tuning

This novel design is of an electronic bell. The

shape of the bell is outlined by a series of

green LEDs while a moving light point on an

arc of red LEDs represents the clapper. Each

time the clapper hits the bell a delicate chime

is generated.

This circuit lends itself well to a bit

of experimentation. The pitch and

sustain of the bell ring can be

adjusted by altering the value of

capacitor C3. Increasing the capaci-

tance will produce a lower note with

a longer sustain.

Elektor Electronics

11/2000

GENERAL INTEREST

12V

100n

BZ1

IC1

SAE800

100n

12V

D65

D66

330p

150 Ω

47k

1N4148

D17 D18 D19 D20 D21 D22

47k

R10

150 Ω

IC3c

≥ 1

12V

D23 D24 D25 D26 D27 D28

X / Y

R11

150 Ω

CTR4

1,2+/1,2-

C20

D29 D30 D31 D32 D33 D34

IC4

4516

IC2

R12

150 Ω

≥ 1

IC3d

D35 D36 D37 D38 D39 D40

20D

R13

150 Ω

D41 D42 D43 D44 D45 D46

100n

D10

IC3a

≥ 1

IC3b

≥ 1

1,2CT=15

1,2CT=0

4514

R14

150 Ω

D11

D47 D48 D49 D50 D51 D52

D12

12V

D13

R15

150 Ω

IC3 = 4001

D14

D53 D54 D55 D56 D57 D58

12V

D15

R16

150 Ω

D59 D60 D61 D62 D63 D64

D16

IC2

IC3

IC4

100µ

25V

100n

000161 - 11

Figure 1. The electronic bell circuit.

in series

with a 1 MΩ preset potentiometer.

Increasing the speed too much how-

ever, will cause the sound of the

chime to go out of step with the dis-

played clapper. In this case the gong

IC will be receiving new trigger

impulses before it has ﬁnished with

the previous chime.

A stabilised 12 V mains unit can

be used to power the circuit. Current

consumption is in the order of

50 – 55 mA.

Ω

Figure 2. Block diagram of the SAE800 Gong IC.

11/2000

Elektor Electronics

The values of R2/C2 govern the

speed of the clapper. Using a smaller

value of capacitor C2 or reducing the

resistance of R2 will speed up the

oscillator and make the light point

move faster. If you want the speed to

be adjustable, R2 could be replaced

by a ﬁxed resistor of 47 k

GENERAL INTEREST

PARTS LIST

Resistors:

R1,R3,R4 = 47k Ω

R2,R7 = 470k Ω

R5,R8 = 1k Ω

R6 = 22k Ω

R9-R16 = 150 Ω

R13

R12

000116-1

Capacitors:

C1 = 100 µ F 25V radial

C2,C4-C8 = 100nF

C3 = 330pF

BZ1

Semiconductors:

D1-D16 = red LED (no high-efficiency)

D17-D64 = green LED (no high-efficiency)

D65,D66 = 1N4148

IC1 = SAE800 Siemens/Inﬁneon (Eurodis)

IC2 = 4514

IC3 = 4001

IC4 = 4516

IC1

Miscellaneous:

S1 = 2-pin header with jumper or switch

BZ1 = AC (Piezo) buzzer with connecting

wires (dia. 24 mm).

PCB, order code 000116-1 (see Readers

services page)

D16

D2 D3

D15

D14

D13

D12

D17

D6 D7 D8 D9 D10

D11

D64

PCB assembly

Shown in Figure 3 is the assembled PCB. Fit-

ting the components should be quite straight-

forward and investing a little time and

patience here will be well repaid in the fin-

ished product. All components with axial

leads should be carefully bent to ﬁt the posi-

tion on the PCB (not forgetting the four wire

jumpers) and then soldered into place. The

best method of mounting the LEDs is to fit

them into their positions on the PCB, ﬂip the

board so that it is track side up and on an

even surface, then carefully solder only one

lead of each LED. Now check that you really

did mount them all the right way round! Also

now you have the chance to slightly re-posi-

tion them, if necessary, to ensure they are

exactly in line with the outlines. Next solder

the second leg of each of the LEDs and ﬁt the

remaining components onto the PCB. The

board should be given a final inspection

before power is applied and the jumper

across S1 is inserted to enable the Gong IC.

(000116-1)

Figure 3. The electronic bell PCB is available

ready-made through our Readers Services.

Elektor Electronics

11/2000

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: