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2-17
——-
LOveL
j--
-
BATT
2
CAPACITOR
Pig.2-24
T
Pig.2-23
By setting a certain voltage level and by changing
the resistance
va-
lue,
it is possible
to measure
the "'time'' for an exposure,
as
shown
in
Fig. 2-24.
This 0-to-level time is transformed
to mechanical
operation
of the shutter
curtains
by the electronic
circuit.
Timing
SW
Timing SW gives an electrical
signal of the
lst curtain departure
to
the circuit,
the signal is given as "earth off''.
However,
the timing SW
turns
off slightly ahead of the lst curtain departure to compensate
a time
lag of the shu:ter mechanism.
Electromagnet
2
Electromagnet
gives a mechanical
signal of the 2nd curtain departure
out of an electrical
signal from the circuit.
The
electromagnet
consists
of iron cores and a dual solenoid (or coil).
The electrical
signal is given as a combination
of ''cutting off'' the
flowing current going through the coil A,
and ''turning on'' the anothér
current
which goes through the coil B.
Asa
result,
total magnetic
at-
traction toward the armature
on the 2nd curtain actuator, terminates
in
an instant.
The
coil B which forms
a weak magnetic
field contrary
to the coil A
in polarity,
supplies
it to the coil A.
As shown
in Fig. 2-25,
this opera-
tion can shorten and stabilize the magnetic
reduction
time
of the electro-
magnet.
This means
the stabilization of the exposure
time at the same
time.
Wb
Fig.2-25
aid SOLENOID OF PENTAX (eT
MAGNETIC FLUX
SINGLE SOLENOID
INCREMENT
AND
REDUCTION
CURVE
2
T
Operation of the governor circuit
This circuit mainly
consists of a sensor
and a DC
amplifier.
A capa-
citor and transistor
TR1
form
the sensor,
and TR2~5
form
the DC am-
plifier with resistors.
With pushing the release
button,
the power
SW turns
''on'"',
timing SW
turns
"off'' and the
lst curtain
starts traveling.
When the timing SW turns "'off'', C1 starts storing the current (i 1)
from the source through Rs and VR2,
resulting in an increment of the
potential difference across
the terminal
of the
Cl.
Then the increment
Lr
"
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