26
CARD
SORTING
MACHINE,
TYPE
82
the capacitor, travel through terminal 17, MC-AU,
terminal 8, contact roll cover switch
2,
terminal
7,
jumper in place of R5, TD-BU, stop
key,
pocket stop
contact, motor control relay,
MC-AL,
terminal 18, 1000
ohm
resistor, terminal 22, 10,000 ohm variable
re-
sistor, terminal 21, to the positive plate.
This discharge keeps the motor control relay
piCked
until the current
flow
from the capacitor falls below
the value required to hold the relay energized. As long
as
the motor control relay remains
piCked,
me MC-BL
point maintains a circuit through the motor relay, and
the motor relay points, in turn, maintain a circuit to
the drive motor. Prolongation of the circuit to the
drive motor in this manner allows the last card in the
machine to be fed to its proper pocket before the
machine stops.
The
10,000 ohm variable resistor in series with the
runout capacitor should be adjusted
so
that the drive
motor will keep running for
.5
to 1 second after the
last card drops in the 9 pocket. Decreasing the effective
value of the variable resistor will prolong the runoue
time; increasing the effective value of the variable
resistor will shorten the runout time.
The runout circuit
is
rendered inoperative in the
event. that the machine
is
stopped through opening of
the pocket stop contact, raising of the contact roll
cover, or depression of the stop
key.
Under
anyone
of these conditions, the machine will coast to a stop
as
soon
as
its inertia
is
overcome
by
friction.
The
47,000 ohm resistor
whiCh
shunts the terminals
of the runout capacitor serves to bleed off the charge
after the machine has been stopped through operation
of
the pocket stop device, raising of the contact roll
cover, or depression of the stop
key.
SORTING
CIRCUITS
BECAUSE
the Type 82 sorter operates at a speed of
650 cards per minute, the sort magnet armature must
be attracted very quickly
(.005 seconds or less)
so
that
the cards will sort properly without being nicked
by
the tips of the chute blades. Relay operation,
as
in the
Type
80 sorter,
is
not dependable at this speed; there-
fore, an
electroniC circuit
is
used.
Not
only does the
electroniC circuit provide the necessary speed of opera-
tion, but it also eliminates burning at the contact roll
and the selector commutator because of the small
amount of current used to control the energization of
the sort magnet.
Before proceeding with
tJhe
study of the sorting
circuits, it may
be
well to review some of the
basiC
principles of electronics
as
an aid to the better under-
standing of these circuits.
1.
In
this presentation, current
flow
shall be estab-
lished synonymous with electron
flow
and shall be
considered
as
flowing from negative to positive.
2.
When
current
flows
through a resistance, the
voltage
is
negative on the end of the resistor where
the current enters and positive on the end where the
current leaves.
3.
When
there
is
no current flowing in a
res~tor
network there will
be
no voltage drops across any given
resistors in that network.
4.
The term "ground" refers to a zero potential
value. Usually the negative power input lead
is
con-
sidered to be
at
ground potential. Voltages measured
from this reference may
be
positive (above ground)
or negative (below ground).
5.
Current or electron
flow
in a vacuum tube or
a gas tube
is
always from the cathode to the anode
(plate) and can take place only when the anode
is
positive in respect to the cathode.
6. The control grid
of
a vacuum tube
is
physiCally
located between me cathode and the anode and acts
as
a valve in regulating the
flow
of electrons from the
cathode to the anode. This control
is
accomplished
by
varying the amount of negative voltage applied to the
grid. Increasing the negative voltage on the grid can
slow down or completely cut off electron
flow
from
cathode to anode, even though the anode (and screen
grid) are positive in respect to the cathode. Decreasing
the negative voltage on the grid can start or speed up
electron flow from cathode to anode
as
long
as
the
anode
is
positive in respect to the cathode.
7.
The constant DC voltage applied between the
control grid and the cathode of a tube
is
called the
bias
voltage.
When
such a voltage
is
applied to the
control grid, it
is
negative with respect to the cathode
potential and
is
called grid bias.
When
such a voltage
is
applied .to the cathode, it
is
positive with respect to
the voltage on the control grid and
is
called cathode
bias.
Regardless of whether grid
bias
or cathode bias
is
used,
the purpose
of
both
is
to make the control grid
negative with respect to the cathode.
8.
The screen grid of a vacuum tube, physiCally
located between the control grid and the anode, may
have a positive voltage applied to it, thus aiding the
anode in attracting electrons away from the cathode.
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