Specifications
CONSTRUCTION
T
he analogue technology is giving
way to the digital technology as
the latter offers numerous advan-
tages. Digital signals are not only free
from distortion while being routed from
one point to another (over various me-
dia), but error-correction is also possible.
Digital signals can also be compressed
which makes it possible to store huge
amounts of data in a small space. The
digital technology has also made remark-
able progress in the field of audio and
video signal processing.
Digital signal processing is being
widely used in audio and video
CD
s and
CD
playing equipment. These compact disks
have brought about a revolution in the
field of audio and the video technology. In
audio
CD
s, analogue signals are first con-
verted into digital signals and then stored
on the
CD
. During reproduction, the digi-
tal data, read from the
CD
, is reconverted
into analogue signals. In case of video sig-
nals, the process used for recording and
reproduction of data is the same as used
for audio
CD
s. However, there is an addi-
tional step involved—both during record-
ing as well as reproduction of the digital
video signals on/from the compact disk.
This additional step relates to the com-
pression of data before recording on the
CD
and its decompression while it is being
read. As video data requires very large
storage space, it is first compressed using
MPEG
- (Motion Picture Expert Group) com-
patible software and then recorded on the
CD
. On reading the compressed video data
from the
CD
, it is decompressed and passed
to the video processor. Thus with the help
of the compression technique huge amount
of video data (for about an hour) can be
stored in one
CD
.
PARTS LIST-1
Semiconductors:
IC1 - LM7805 voltage regulator +5V
Resisters (All ¼W, ±5% metal/carbon film,
unless stated otherwise):
R1 - 68 ohm
R2, R3 - 1 kilo-ohm
VR1 - 100 ohm cermet (variable resistor)
Capacitors:
C1 - 1µF paper (unipolar)
C2 - 10µF, 16V electrolytic
Miscellaneous:
X1 - 230V AC primary to 12V-0-12V, 1A sec.
transformer
S1, S2 - Push-to-on tactile switch
- MPEG decoder card (Sony Digital Tech.)
- TV modulator (optional)
- AF plugs/jacks (with screened wire)
- Co-axial connectors, male/female
- Co-axial cable
CONVERSION OF AUDIO CD PLAYER
TO VIDEO CD PLAYER I
G.S. SAGOO
Conversion
An audio
CD
player, which is used to play
only audio
CD
s, can be converted to play
the video
CD
s as well. Audio
CD
players
have all the required mechanism/functions
to play video
CD
s, except an
MPEG
card,
which is to be added to the player. This
MPEG
card is readily available in the mar-
ket. This
MPEG
card decompresses the data
available from the audio
CD
player and con-
verts it into proper level of video signals
before feeding it to the television.
Construction
Step-by-step conversion of audio
CD
player
to video
CD
player is described with refer-
ence to Fig. 1.
Step 1. Connection of
MPEG
card
to
TV
and step-down power trans-
former to confirm proper working of
the
MPEG
card.
●
Connect
IC
7805, a 5-volt regulator, to the
MPEG
card. Please check for correct pin
assignments.
●
Connect audio and video outputs of the
Fig. 1: Complete schematic layout and connection diagram for conversion of
Audio CD to Video CD player
Fig 2: Photograph of TV scene
PUNERJOT SINGH MANGAT
14