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Drive
System
Circuit
Sorvall®
CentrifugesP.C.
board
No.
50155
provides
the
logic
circuitry
that
controls
relay
K407.
The
incom¬ing
signal
from
the
tachometer
generator
is
processed
by
comparator
Z2
and
associatedcircuitry
to
generate
a
dc
signal
having
a
level
that
is
proportional
to
the
actual
rpm
ofthe
drive
motor.
This
signal
is
compared
against
a
threshold
level
in
comparator
Zl,
setby
potentiometer
R14.
The
threshold
level
voltage
is
set
for
900
rpm
during
accelerationand
700
rpm
during
deceleration.
The
output
of
operational
amplifier
Z3
drives
transis¬tor
Ql.
causing
it
to
switch
ON
and
OFF.
This
switching
controls
relay
K210
whichcontrols
delay
relay
K206,
which,
in
turn.
controls
the
switching
of
transfer
relay
K407.Comparator
Zl
responds
to
setting
of
potentiometer
Rl
10.
that
modulates
the
drivemotor
power
through
relay
K407.4-10.
Door
Interlock
CircuitDoor
solenoid
L301
is
located
beneath
the
top
deck
cover
opposite
the
door
handle.Under
normal
operating
conditions,
the
door
interlock
circuit
allows
the
door
to
beopened
only
when
the
rotor
is
spinning,
the
main
circuit
breaker
is
closed
and
power
isapplied
to
the
centrifuge.The
plunger
ofL301
is
normally
fully
extended
and
functions
as
a
locking
bolt
that
locksthe
door
when
it
is
properly
closed.
When
solenoid
L301
is
energized,
the
plunger
isretracted
and
the
door
is
unlocked,
then
spring
tension
causes
the
door
to
pop
upward.In
the
RC-5,
when
the
centrifuge
is
in
the
HOLD
mode
and
the
drive
motor
speed
is
atzero
rpm,
28
Vac
from
T201
is
applied
to
bridge
rectifier
CR203.
Rectifier
CR203
sendsa
pulsating
28
Vdc
across
the
closed
contacts
11-1
of
relay
Kl
to
be
filtered
at
capacitorC205.
then
energizes
the
coil
of
solenoid
L301
and
light
door
indicator
DS108.
In
theRUN
mode,
when
the
drive
motor
speed
becomes
greater
than
100
rpm.
relay
Kl
isdeenergized,
causing
the
28
Vdc
from
the
bridge
rectifier
to
be
removed
from
the
coil
ofdoor
solenoid
L301.
which
becomes
deenergized.When
door
solenoid
L301
is
deenergized.
the
spring-loaded
solenoid
plunger
is
retractedand
outward,
locking
the
centrifuge
chamber
door
and
causing
the
DOOR
indicatorlamp
DS108
to
be
extinguished.The
door
may
be
opened
by
pressing
S 108A
DOOR
switch,
a
momentary
switch.
SwitchS108
momentarily
energizes
K204,
door
relay,
which
will
allow
28
Vac
from
transformerT201
to
pass
across
contacts
4-7
to
bridge
rectifier
CR203
which
sends
a
pulsating28
Vdc
to
be
filtered
at
C205,
then
energizes
the
coil
of
door
solenoid
L301
and
lightDOOR
Indicator
lamp
DS108.When
door
solenoid
L301
is
energized,
the
spring-loaded
solenoid
plunger
is
retractedand
the
centrifuge
door
is
unlocked.When
the
centrifuge
door
is
opened,
the
door
microswitch
S301
closes,
applying
115Vac
on
the
coil
of
door
relay
K204,
causing
it
to
remain
energized.
The
DOOR
indicatorDS108
lights
and
the
spring-loaded
solenoid
plunger
is
retracted.NOTEIf
momentary
door
switch
S108A
is
pressed
and
held
for
2-3
seconds,
thecircuit
is
locked
out
as
a
safety
feature
to
protect
the
door
relay.4-28
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