e005028.pdf

CONSTRUCTION KIT

Record/Playback Module

A solid-state recorder

This device is an outstanding choice for a talking doorbell or any other

application in which a short text of your own choice must be repeated.

The length of the message is naturally limited, but it can be increased by

coupling several modules in series.

This type of record/playback unit always has

a special kind of fascination. After all, it’s not

that long ago that the recording and playback

of speech or music without the aid of moving

parts was only possible in science ﬁction sto-

ries. However, in the past few years these

‘solid-state’ recorders have become familiar

objects. Since there are innumerable possible

applications for such a device, both commer-

cially and in the household, Velleman have

include one in their catalogue of construction

kits, and at a reasonable price. In order to give

our readers an idea of the features of

this record/playback module, we

assembled one in the Elektor labs.

digits of the part number indicate

the number of seconds’ worth of

information that can be stored in the

IC. The IC used in the Velleman kit is

a rather old version, the ISD1020,

with a storage time of 20 seconds.

All of these voice recorder ICs

have non-volatile analogue memo-

ries that can hold the stored audio

for at least ten years without power.

In addition, the chip includes a

microphone preampliﬁer and an out-

Only one IC

For several years now, the firm ISD

has been marketing a series of ICs

that contain a complete solid-state

recorder. This consists of the

ISDD10XX, ISD14XX and ISD25XX

series of components. The last two

Elektor Electronics

5/2000

CONSTRUCTION KIT

BANK SELECT

POWER

SUPPLY

AUX IN

SP OUT

AN OUT

AN IN

ADDRESS

BUFFER

ANALOG

STORAGE

ARRAY

MIC

FILTER

ANALOG TRANSCEIVER

FILTER

MUX

AGC

P/R PD

DEVICE CONTROL

EOM

INTERNAL CLOCK

ISD 1020

REC

MODE

NORMAL

RECORD

REC

OUT

LAST UNIT

PLAY

OUT

FLIP-FLOP

START NEXT UNIT

OUT

START

SET

RESET

STOP

005067 - 11

REPEAT

REPEAT FROM LAST UNIT

Figure 1. Block diagram of the record/playback module built around the ISC1020 IC.

put ampliﬁer, so a microphone and a

(small) loudspeaker can be con-

nected directly to the IC. The exter-

nal components are thus limited to a

few resistors and capacitors, plus

two switches.

In the Velleman kit you will also

ﬁnd a number of transistors, since a

few extra functions have been

added. These allow several modules

to be connected in cascade, allow

the message to automatically be

repeated periodically, and allow ﬁve

different sections of the recording to

be selected (‘bank selection’). The

block diagram in Figure 1 shows

how the device can be set up for the

various types of playback.

The circuit can be powered from

batteries (6 V) or from a standard

mains adapter (9 - 12 V AC ). The cur-

rent consumption is only a few tens

of milliamps. In the standby mode,

the current consumption is negligible.

child’s play. The printed circuit board

is clearly laid out and fortunately not

all too small, so even the less expe-

rienced solder artist should not have

any problems with it. An electret

microphone is supplied with the kit,

but remarkably enough there is no

loudspeaker, so you will have to sup-

ply your own. Fortunately, these

miniature Japanese loudspeakers

are available for next to nothing.

Once we put together the circuit

and connected the power source, it

started to work right away. This is of

course the way things should be, but

experience teaches that it is not

always the case.

Using the record/playback module

is simplicity itself.

position.

– Brieﬂy press the Start button. The recorded

message is played back. The playback

stops automatically at the end of the mes-

sage.

It’s thus just as easy to use the circuit as it is

to build it. If you are looking for a way to give

your doorbell or some toy an original and

‘expressive’ character, this is exactly what

you need.

You shouldn’t expect too much in terms of

sound quality, which is around the level of

that of a telephone. However, this is easily

adequate for most applications.

(005067-1)

Text (Dutch original): S. van Rooij

A complete construction kit for the Record/Play-

back module can be obtained from Velleman, Bel-

gium. The kit, part number K4400, is priced at

US$59.95 and available from electronics retail

shops). In the UK, a selection of Velleman kits is

stocked by Maplin.

Recording:

– Set the record/playback switch to

the ‘record’ position.

– Press and hold the Start button,

and speak your message into the

microphone. A LED shows when

the maximum recording time is

reached.

Construction

and operation

The kit includes an extensive set of

instructions for putting it together,

which makes assembling the circuit

Velleman contact information:

Velleman Components, Legen Heirweg 33, B-9890

Gavere, Belgium. Fax: (+32) 9 384 6702.

Email: order@velleman.be

Internet: http://www.velleman.be

Playback:

– Set the switch to the ‘playback’

5/2000

Elektor Electronics

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