Dual 704 - Speed Regulation

Fig.
3
Rotor
a.)
b.)
d.
Sp1
Sp2
Sp3
Sp4
H1 H2
270°
202,5 °
Transistor T 15 becomes
conductive and cur-
rent flows through a part of
coil 2, so that
a south pole is
formed while current
flows
through a part of
coil 4 in counter direc-
tion which acts as north pole. The
rotation
of the rotor through 22.5 0
moves the subse-
quent south pole of the
annular magnet on
the Hall generator H 1 (Fig. 3
c). Transistor
T 16 becomes conductive, coil 1 is the south
pole and coil 3 forms a northpole. By a fur-
ther
rotation
through 22.5°
the south pole
moves via
Hall generator H 2, which controls
Transistor T 14 (Fig. 3 d). Coil 2 becomes
the north pole, coil 4 the south pole.
Speed
Regulation
The rotor
rotates with a
toothed disk
having
200 teeth. A
magnetic tape
is cemented
round
the motor
flange. On one
side the tape
has
200 north
poles on the
other side 200
south
poles. The north
poles are
arranged directly
opposite the rotor
center. A coil
is mounted
in
the vicinity of
the
magnetic tape and
the
toothed disk. A
changing
magnetic
field is
produced
by the
rotating
toothed disk. This
magnetic field
induces in
the coil a
voltage
with
the
corresponding
frequency. This fre-
quency is
111 Hz at a
rotational
speed of
33.3 rpm.
135° 67,5 °
22,5° 0
The pulses produced by induction are lead
to the input amplifier consisting
of tran-
sistor T 1 and T 2. The signal across emit-
ter and collector of transistor T 2 is lead
to the frequency doubler. The doubled pul-
ses are applied to transistor 5 (via capa-
citor C 8) which, together with transistor
T 6,
works am a mono flop. The rectangular
pulses thus gained
are integrated via re-
sistors R
23, R 25, R 26 and capacitors
C 10, C 11, C 12 and produce a base
voltage
of transistor T 9. The pulse/pause ratio of
the monoflop can be varied by
controls R 45
(basic setting monoflop), R 20 (coarse speed
control 45 rpm),
R 22 (coarse speed control
33 rpm) and R
21 (fine speed adjustment).
As
a result
also the
potential across
the
base of transistor T 9
changes after inte-
gration T 9 and T 10
take the form of a dif-
ferential
amplifier which controls - via
the
collector of transistor
T 9 - the base
of
T 7 which,
together with T 8 also takes
the
form of a
differential
amplifier. The ampli-
fied control voltage
is lead from the
col-
lector of
transistor T 8 to
the base of T 12
via
resistor R 37. The
transistor T 12 and
T 13,
which are connected am an
emitter fol-
lower, control the
current for
the four
switching
transistors. The
maximum starting
current is
controlled by R 40
via transistor
T 11.
7