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Claims  |
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Having described the invention, the following is claimed:
1. An apparatus for use with either a first solenoid requiring a first
holding current of a first magnitude or a second solenoid requiring a
second holding current of a second magnitude which is smaller than the
magnitude of the first holding current, said apparatus comprising output
means connectable with either the first solenoid or the second solenoid,
and control circuit means connected with said output means for providing
the first holding current of the first magnitude to said output means when
the first solenoid is connected with said output means and for providing
the second holding current of the second magnitude to said output means
when the second solenoid is connected with said output means, said control
circuit means being ineffective to provide the second holding current of a
second magnitude to said output means when the first solenoid is connected
with said output means, said control circuit means being ineffective to
provide the first holding current of a first magnitude to said output
means when the second solenoid is connected with said output means, said
control circuit means including detector means connected with said output
means for detecting which one of the first and second solenoids is
connected with said output means, said detector means being operable to
provide a first output when said first solenoid is connected with said
output means, said detector means being effective to provide a second
output which is different than the first output when said second solenoid
is connected with said output means, and current control means connected
with said detector means and said output means for providing a holding
current of the first magnitude to said output means in response to said
detector means providing the first output and for providing a holding
current of the second magnitude in response to said detector means
providing the second output.
2. An apparatus as set forth in claim 1 wherein said control circuit means
includes means connected with said output means for providing an initial
voltage at said output means for a first period of time in response to an
enable signal, said current control means includes means for changing the
voltage at said output means in a first manner in response to said
detector means detecting that the first solenoid is connected with said
output means and for changing the voltage at said output means in a second
manner in response to said detector means detecting that the second
solenoid is connected with said output means.
3. An apparatus as set forth in claim 1 wherein said control circuit means
includes means connected with said output means for effecting initial
energization of the first solenoid with a first voltage when the first
solenoid is connected with said output means and for effecting initial
energization of said second solenoid with the first voltage when said
second solenoid is connected with said output means.
4. An apparatus as set forth in claim 3 wherein said detector means
includes means connected with said output means for detecting whether the
first solenoid or the second solenoid is connected with said output means
as a function of a rate of flow of current to the solenoid connected with
said output means during initial energization of the solenoid.
5. An apparatus as set forth in claim 1 wherein said control circuit means
further includes fault detection circuit means connected with said output
means for detecting a fault in the first or the second solenoid during
initial energization of the first or the second solenoid as a function of
the rate of flow of current to the solenoid connected with said output
means during initial energization of the solenoid.
6. An apparatus as set forth in claim 1 wherein said current control means
includes multivibrator means connected with said output means for
providing an output having a first duty cycle when said detector means
detects that the first solenoid is connected with said output means and
for providing an output having a second duty cycle when said detector
means detects that the second solenoid is connected with said output
means.
7. An apparatus as set forth in claim 1 wherein said current control means
includes means connected with said output means and said detector means
for charging a capacitor to a predetermined level and for changing the
amount of holding current supplied to said output means as a function of
the amount of time required to charge the capacitor to the predetermined
level, said detector means being operable to enable the capacitor to be
charged to the predetermined level in a first period of time when the
first solenoid is connected with said output means and to enable the
capacitor to be charged to the predetermined level in a second period of
time when the second solenoid is connected with said output means, said
first period of time being of a different duration than said second period
of time.
8. An apparatus as set forth in claim 1 wherein said current control means
includes switch means connected with said detector means and operable
between a conducting condition and a nonconducting condition and means for
effecting operation of said switch means between the conducting and
nonconducting conditions at a first rate in response to said detector
means detecting that the first solenoid is connected with said output
means and for effecting operation of said switch means between the
conducting and nonconducting conditions at a second rate in response to
said detector means detecting that the second solenoid is connected with
said output means.
9. An apparatus for use with either a first solenoid having first
characteristics and requiring a first holding current or a second solenoid
having second characteristics and requiring a second holding current which
is different than the first holding current, said apparatus comprising
output means connectable with either the first solenoid or the second
solenoid, means connected with said output means for initially energizing
the one of the first and second solenoids connected with said output means
to effect operation of the solenoid connected with said output means from
an unactuated condition to an actuated condition, means connected with
said output means for detecting whether a characteristic of the initial
energization of the solenoid connected with said output means corresponds
to a characteristic of initial energization of the first solenoid or a
characteristic of initial energization of the second solenoid, and means
connected with said output means for providing the first holding current
to the solenoid connected with said output means in response to detecting
that the initial energization of the solenoid connected with said output
means has a characteristic corresponding to a characteristic of initial
energization of the first solenoid and for providing the second holding
current to the solenoid connected with said output means in response to
detecting that the initial energization of the solenoid connected with
said output means has a characteristic corresponding to a characteristic
of initial energization of the second solenoid.
10. An apparatus as set forth in claim 9 wherein said means for providing
the first holding current and for providing the second holding current
includes multivibrator means which is connected with said output means and
is operated with a first duty cycle to provide the first holding current
and is operated with a second duty cycle to provide the second holding
current.
11. An apparatus as set forth in claim 9 wherein said means for detecting
whether a characteristic of the initial energization of the solenoid
connected with said output means corresponds to a characteristic of
energization of the first solenoid or a characteristic of energization of
the second solenoid includes means connected with said output means for
sensing a characteristic which is a function of the rate of flow of
current through the solenoid connected with said output means and which
has a first magnitude during initial energization of the first solenoid
and a second magnitude during initial energization of the second solenoid.
12. An apparatus as set forth in claim 9 wherein said means for providing a
first holding current and for providing a second holding current includes
switch means connected with said output means and operable between a
conducting condition and a nonconducting condition and means for effecting
operation of said switch means between the conducting and nonconducting
conditions at a first rate to provide the first holding current and for
effecting operation of said switch means between the conducting and
nonconducting conditions at a second rate to provide the second holding
current.
13. An apparatus as set forth in claim 9 further including fault detection
means connected with said output means for detecting an excessive rate of
current flow during initial energization of the solenoid connected with
said output means and for interrupting initial energization of a solenoid
connected with said output means in response to detection of an excessive
rate of current flow.
14. An apparatus for use with either a first solenoid requiring a first
holding current or a second solenoid requiring a second holding current
which is smaller than the first holding current, said apparatus comprising
output means connectable with either the first solenoid or the second
solenoid, said output means including first and second terminals
connectable with either the first solenoid or the second solenoid, input
means for receiving an enable signal, first switch means connected with
said input means and the first terminal of said output means and operable
from a nonconducting condition to a conducting condition in response to
said input means receiving an enable signal, second switch means connected
with the second terminal of said output means and operable between a
conducting condition and a nonconducting condition, said first and second
switch means completing an electrical circuit to energize a solenoid
connected with the first and second terminals of said output means when
said first and second switch means are in the conducting condition,
multivibrator means connected with said input means and said second switch
means for effecting operation of said second switch means from the
nonconducting condition to the conducting condition for an initial period
of time in response to said input means receiving an input signal to
thereby effect initial energization of a solenoid connected with the first
and second terminals of said output means, detector means connected with
said output means for detecting whether a characteristic of the initial
energization of the solenoid connected with the first and second terminals
corresponds to a characteristic of initial energization of the first
solenoid or the second solenoid, and means connected with said
multivibrator means and said detector means for effecting operation of
said multivibrator means to change said second switch means between the
conducting and nonconducting conditions at a first rate in response to
said detector means detecting a characteristic of the initial energization
which corresponds to a characteristic of initial energization of the first
solenoid to enable the first holding current to be conducted through said
first and second switch means and for effecting operation of said
multivibrator means to change said second switch means between the
conducting and nonconducting conditions at a rate which is different than
the first rate to change said second switch means between the conducting
and nonconducting conditions at a second rate in response to said detector
means detecting a characteristic of initial energization which corresponds
to a characteristic of initial energization of the second solenoid to
enable the second holding current to be conducted through said first and
second switch means.
15. An apparatus as set forth in claim 14 wherein said means for effecting
operation of said multivibrator means to change said second switch means
between the conducting and nonconducting conditions at a first rate and
for effecting operation of said multivibrator means to change said second
switch means between the conducting and nonconducting conditions at a
second rate includes means for charging a capacitor connected with said
multivibrator means to a predetermined level and means for causing the
time required to charge the capacitor to the predetermined level to be a
first period of time in response to said detector means detecting that a
characteristic of initial energization of the solenoid connected with the
first and second terminals corresponds to a characteristic of the first
solenoid and for causing the time required to charge the capacitor to the
predetermined level to be a second period of time in response to said
detector means detecting that a characteristic of initial energization of
the solenoid connected with the first and second terminals corresponds to
a characteristic of the second solenoid.
16. An apparatus comprising a solenoid having either a large or a small
initial energization current magnitude, circuit means connected with said
solenoid for providing an electrical current to initially energize said
solenoid, and sensor means connected with said circuit means for sensing
whether the magnitude of the electrical current provided by said circuit
means during initial energization of said solenoid corresponds to the
large or the small initial energization current magnitude; said circuit
means including means for providing a first electrical holding current of
a first magnitude to maintain said solenoid energized in response to said
sensor means sensing initial energization of said solenoid with an
electrical current of a large magnitude and for providing a second
electrical holding current of a second magnitude to maintain said solenoid
energized in response to said sensor means sensing initial energization of
said solenoid with an electrical current of a small magnitude.
17. An apparatus as set forth in claim 16 wherein said means for providing
a first electrical current of a first magnitude to maintain said solenoid
energized in response to said sensor means sensing initial energization of
said solenoid with an electrical current of a large magnitude and for
providing electrical current of a second magnitude to maintain said
solenoid energized in response to said sensor means sensing initial
energization of said solenoid with an electrical current of a small
magnitude includes multivibrator means connected with said solenoid for
providing an output having a first duty cycle when said sensor means
senses initial energization of said solenoid with an electrical current of
a large magnitude and for providing an output having a second duty cycle
when said sensor means senses initial energization of said solenoid with
an electrical current of a small magnitude.
18. An apparatus as set forth in claim 16 wherein said means for providing
a first electrical current of a first magnitude to maintain said solenoid
energized in response to said sensor means sensing initial energization of
said solenoid with an electrical current of a large magnitude and for
providing an electrical current of a second magnitude to maintain said
solenoid energized in response to said sensor means sensing initial
energization of said solenoid with an electrical current of a small
magnitude includes means for applying a voltage to said solenoid and means
for changing the voltage applied to said solenoid in a first manner in
response to said sensor means sensing that said solenoid is initially
energized with an electrical current of a large magnitude and for changing
the voltage applied to said solenoid in a second manner in response to
said sensor means sensing that said solenoid is initially energized with
an electrical current of a small magnitude.
19. An apparatus as set forth in claim 16 wherein said means for providing
an electrical current of a first magnitude to maintain said solenoid
energized in response to said sensor means sensing initial energization of
said solenoid with an electrical current of a large magnitude and for
providing an electrical current of a second magnitude to maintain said
solenoid energized in response to said sensor means sensing initial
energization of said solenoid with an electrical current of a small
magnitude includes a capacitor and means for charging said capacitor to a
predetermined level and for changing the electrical current used to
maintain said solenoid energized as a function of the amount of time
required to charge said capacitor to the predetermined level.
20. An apparatus as set forth in claim 16 wherein said means for providing
an electrical current of a first magnitude to maintain said solenoid
energized in response to said sensor means sensing initial energization of
said solenoid with an electrical current of a large magnitude and for
providing an electrical current of a second magnitude to maintain said
solenoid energized in response to said sensor means sensing initial
energization of said solenoid with an electrical current of a small
magnitude includes switch means connected with said sensor means and
operable between a conducting condition and a nonconducting condition and
means for effecting operation of said switch means between the conducting
and nonconducting conditions at a first rate in response to said sensor
means sensing initial energization of said solenoid with an electrical
current of a large magnitude and for effecting operation of said switch
means between the conducting and nonconducting conditions at a second rate
in response to said sensor means sensing initial energization of said
solenoid with an electrical current of a small magnitude.
21. An apparatus comprising a solenoid having a first initial energization
characteristic or either a first magnitude or a second magnitude, output
means connected with said solenoid, said output means including first and
second terminals connected with said solenoid, input means for receiving
an enable signal, first switch means connected with said input means and
the first terminal of said output means and operable from a nonconducting
condition to a conducting condition in response to said input means
receiving an enable signal, second switch means connected with the second
terminal of said output means and operable between a conducting condition
and a nonconducting condition, said first and second switch means
completing an electrical circuit to energize said solenoid when said first
and second switch means are in the conducting condition, multivibrator
means connected with said input means and said second switch means for
effecting operation of said second switch means from the nonconducting
condition to the conducting condition for an initial period of time in
response to said input means receiving an input signal to thereby effect
initial energization of said solenoid, detector means connected with said
output means for detecting whether a characteristic of initial
energization of said solenoid corresponds to the first magnitude or the
second magnitude, and means connected with said multivibrator means and
said detector means for effecting operation of said multivibrator means to
change said second switch means between the conducting and nonconducting
conditions at a first rate in response to said detector means detecting a
characteristic of initial energization of the first magnitude to enable a
first holding current to be conducted through said first and second switch
means and for effecting operation of said multivibrator means to change
said second switch means between the conducting and nonconducting
conditions at a rate which is different than the first rate to change said
second switch means between the conducting and nonconducting conditions at
a second rate in response to said detector means detecting a
characteristic of initial energization of the second magnitude to enable a
second holding current to be conducted through said first and second
switch means.
22. An apparatus as set forth in claim 21 wherein said means for effecting
operation of said multivibrator means to change said second switch means
between the conducting and nonconducting conditions at a first rate and
for effecting operation of said multivibrator means to change said second
switch means between the conducting and nonconducting conditions at a
second rate includes a capacitor connected with said multivibrator means,
means for charging said capacitor to a predetermined level, and means for
causing the time required to charge the capacitor to the predetermined
level to be a first period of time in response to said detector means
detecting that the characteristic of initial energization of said solenoid
corresponds to the first magnitude and for causing the time required to
charge the capacitor to the predetermined level to be a second period of
time in response to said detector means detecting that the characteristic
of initial energization of said solenoid corresponds to the second
magnitude. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
The present invention relates to a solenoid control circuit and, more
specifically, to a solenoid control circuit which may be used with either
a first solenoid requiring a relatively large holding current or a second
solenoid requiring a relatively small holding current.
A known apparatus utilizes divert gates to direct sheet material articles
toward receiving locations. The divert gates are moved between actuated
and unactuated positions by solenoids. The solenoids used with the divert
gates may be obtained from different manufacturers and have different
electrical characteristics. Even though the solenoids used with the divert
gates may have different electrical characteristics, it would be
advantageous to be able to use the same solenoid control circuitry to
control the operation of the solenoids.
SUMMARY OF THE INVENTION
Improved solenoid control circuitry can be used with either a first
solenoid requiring a relatively large holding current or a second solenoid
requiring a relatively small holding current. The solenoid control
circuitry includes an output which can be connected with either one of the
solenoids. The solenoid control circuitry is operable to provide a
relatively large holding current to when the first solenoid requiring the
relatively large holding current is connected with the output. The
solenoid control circuitry is operable to provide a relatively small
holding current when the second solenoid requiring the relatively small
holding current is connected with the output.
The solenoid control circuitry is operable to initially energize a solenoid
connected with the output to effect operation of the solenoid from an
unactuated condition to an actuated condition. During initial energization
of the solenoid connected with the solenoid control circuitry output, a
detector detects whether a characteristic of the initial energization of
the solenoid corresponds to a characteristic of initial energization of
the first solenoid or a characteristic of initial energization of the
second solenoid. The solenoid control circuitry provides a first holding
current to the solenoid connected with the output in response to detecting
an initial energization characteristic corresponding to the first
solenoid. The solenoid control circuitry provides a second holding
current, which is less than the first holding current, to the solenoid
connected with the output in response to detecting an initial energization
characteristic corresponding to the second solenoid.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and further features of the invention will become more
apparent upon a consideration of the following description taken in
connection with the accompanying drawings wherein:
FIG. 1 is a schematic illustration of solenoid control circuitry
constructed in accordance with the present invention and capable of being
used with either a first solenoid requiring a relatively large holding
current or a second solenoid requiring a relatively small holding current;
FIG. 2 is a plot illustrating the initial energization and holding current
required by the first solenoid and the initial energization and holding
current required by the second solenoid;
FIGS. 3A and 3B are a detailed schematic illustration of the solenoid
control circuitry of FIG. 1;
FIG. 4 is a plot illustrating the voltage at an output terminal of a
multivibrator in the solenoid control circuitry of FIGS. 3A and 3B when
the first solenoid requiring the relatively large holding current is
connected with the solenoid control circuitry; and
FIG. 5 is a plot illustrating the voltage at the output terminal of the
multivibrator in the solenoid control circuitry of FIGS. 3A and 3B when
the second solenoid requiring the relatively small holding current is
connected with the solenoid control circuitry.
DESCRIPTION OF ONE SPECIFIC PREFERRED EMBODIMENT
General Description
Solenoid control circuitry 10 (FIG. 1) is used to effect operation of a
solenoid 12. The solenoid 12 may be either a first solenoid requiring a
relatively large holding current or a second solenoid 12a requiring a
relatively small holding current. Thus, the solenoid control circuitry 10
can be used with either one of two solenoids 12 or 12a even though the
solenoids have different electrical characteristics.
The solenoid 12 12 may be connected with any suitable apparatus for
performing any desired function. For example, the solenoid 12 or 12a may
be used in association with a divert gate (not shown) which is movable
from an unactuated condition to an actuated condition to divert sheet
material article to a desired receiving location. To effect rapid
operation of the divert gate from the unactuated condition to the actuated
condition, the solenoid 12 or 12a is initially energized with a relatively
large current. In order to enhance the operating life of the solenoid 12
or 12a, the relatively large current used to effect initial energization
of the solenoid is reduced to a smaller holding current after the solenoid
has been operated.
The solenoid 12 or 12a may be either one of two different solenoids. Thus,
the solenoid 12 may be a first one of two solenoids. The first solenoid
requires a relatively large initial energization current, indicated by a
portion 16 of a curve 18 (FIG. 2). The first solenoid also requires a
relatively large holding current, indicated by a portion 20 of the curve
18.
However, the solenoid 12 or 12a may be a second one of two solenoids, that
is, a solenoid 12a. The second solenoid 12a requires a relatively small
initial energization current, indicated by a portion 22 of a curve 24
(FIG. 2). The second solenoid 12a also requires a relatively small holding
current, indicated by a portion 26 of the curve 24.
For example, in one specific embodiment of the invention, the solenoid
control circuitry 10 was capable of being used with a first solenoid
requiring an initial energization current having a value, indicated at 28
in FIG. 2, of approximately 2.54 amps. The first solenoid 12 requires a
relatively large holding current, indicated at 20 in FIG. 2, of about
0.930 amps. Instead of the first solenoid, the solenoid control circuitry
10 could be used with a second solenoid 12a requiring an initial
energization current having a value, indicated at 30 in FIG. 2, of
approximately 1.33 amps. The second solenoid 12a requires a relatively
small holding current, indicated at 26 in FIG. 2, of about 0.730 amps.
The initial energization time for both of the solenoids is the same, as
indicated by an arrow 32 in FIG. 2. In this specific instance, the time 32
required for initial energization of either the first solenoid or the
second solenoid was approximately 27 milliseconds. The holding time for
the first solenoid and the second solenoid is the same and is indicated by
an arrow 34 in FIG. 2. The duration of the holding time, indicated by the
arrow 34 in FIG. 2, will depend upon the apparatus with which the
solenoids are used. Of course, the specific initial energization current,
initial energization time and holding current will depend on the specific
characteristics of the specific solenoid 12 with which the control
circuitry 10 is used.
In regard to the specific solenoids having the characteristics previously
described and having characteristics corresponding to the plot of FIG. 2,
the first solenoid 12 requiring the relatively large holding current was
manufactured by RAM Co. of 64 North 800 East, St. George, Utah 84770,
U.S.A. and had a part No. of 40R101102. This specific first solenoid had a
resistance of approximately 13.6 ohms. The first solenoid had a power
rating at a 100% duty cycle of 14 watts, a continuous voltage rating of 14
volts, and a continuous current rating of 1 amp. The second solenoid 12a
requiring the relatively small holding current was manufactured by Lucas
Ledex Inc. of 801 Scholz Drive, Vandalia, Ohio 45377, U.S.A. and had a
part No. of 192895-001. This specific second solenoid had a resistance of
approximately 25.7 ohms. In addition, the second solenoid had a power
rating at a 100% duty cycle of 14.0 watts, a continuous voltage rating of
14 volts, and a continuous current rating of 0.76 amps.
It should be understood that other known solenoids could be utilized in
place of the two specific solenoids previously described. The solenoids
which are substituted for the two solenoids whose characteristics were
previously described may not have characteristics which are in the same
relationship to each other as the characteristics of the previously
described solenoids. It should also be understood that the foregoing
description of two specific solenoids having particular characteristics
has been provided herein and will be referred to hereinafter, for purposes
of clarity of description and not for purposes of limitation of the
invention. It is contemplated that the solenoid control circuitry 10 may
be constructed in accordance with the present invention so as to be used
with any one of many different solenoids having many different
characteristics.
It should also be understood that solenoids from more than two different
manufacturers may be used with the solenoid control circuitry. Thus, in
one specific instance, a third manufacturer provided a third solenoid
which had electrical characteristics similar to the characteristics of the
first solenoid. Any one of these three solenoids could be used with the
solenoid control circuitry 10.
The solenoid control circuitry 10 includes a detector 40 (FIG. 1) which
detects a characteristic of initial energization of the solenoid 12 or
12a. Although the solenoid control circuitry 10 could be constructed so as
to detect one or more of many different characteristics of initial
energization of the solenoid 12 or 12a, the detector 40 detects whether a
relatively large initial energization current or a relatively small
initial energization current is conducted to the solenoid 12 during
initial energization of the solenoid or 12a.
If a relatively large initial energization current is detected by the
detector 40, the solenoid control circuitry 10 provides the relatively
large holding current 20 (FIG. 2) required by the first solenoid. If a
relatively small initial energization current is detected by the detector
40, the solenoid control circuitry 10 provides the relatively small
holding current 26 (FIG. 2) required by the second solenoid. In either
case, the holding current is substantially less than the current which is
required for initial energization of the solenoid. By providing holding
current which is less than the initial energization current, the solenoid
operating life is enhanced without impairing the ability of the solenoid
to be rapidly operated.
During initial energization of either the first solenoid 12 requiring a
relatively large holding current 20 (FIG. 2) or the second solenoid 12a
requiring a relatively small holding current 26, the solenoid control
circuitry 10 is effective to detect a fault in the solenoid 12 or 12a. If
a fault is detected in the solenoid 12, the solenoid control circuitry 10
interrupts initial energization of the solenoid. Thus, as soon as a fault
is detected in the solenoid 12 or 12a during initial energization of the
solenoid, the solenoid control circuitry 10 interrupts energization of the
solenoid to minimize the possibility of damage to the solenoid control
circuitry and/or related apparatus.
Solenoid Control Circuitry--General Description
The solenoid control circuitry 10 includes an output, indicated
schematically at 44 in FIG. 1, which is connectable with either the first
solenoid 12 requiring a relatively large holding current 20 (FIG. 2) or
the second solenoid 12a requiring a relatively small holding current 26.
The solenoid control circuitry 10 also has an input 46 (FIG. 1) at which
an enable signal is received. An enable indicator 48 indicates the
presence of an enable signal at the input 46.
An H-bridge circuit 50 (FIG. 1) effects initial energization of the
solenoid 12 or 12a connected to the output 44 in response to an enable
signal at the input 46. The H-bridge circuit 50 uses the same voltage (+42
V) to effect initial energization of either the first solenoid requiring
the relatively large holding current or the second solenoid requiring the
relatively small holding current. Thus, initial energization of the first
solenoid or the second solenoid is accomplished in the same manner by the
solenoid control circuitry 10. Of course, the specific initial
energization voltage will depend on the specific characteristics of the
solenoids which may be used with the solenoid control circuitry 10.
The duration of the initial energization of the solenoid 12 or 12a is
determined by a one-shot multivibrator 53. The one-shot multivibrator 53
is connected with an astable multivibrator 52. The astable multivibrator
52 is connected with the H-bridge circuit 50 through a push-pull amplifier
or driver 54. The duration of the initial energization of the solenoid 12
or 12a is the same whether the solenoid is the first solenoid which
requires a relatively large holding current or the second solenoid which
requires the relatively small holding current. Thus, both solenoids are
initially energized for the period of time indicated at 32 in FIG. 2.
Until initial energization of the solenoid 12 or 12a is undertaken, the
solenoid control circuitry 10 (FIG. 1) does not know whether the first
solenoid requiring a relatively large holding current or the second
solenoid requiring a relatively small holding current has been connected
with the output 44. During initial energization, the detector 40 detects
whether the solenoid 12 or 12a is the first solenoid 12 requiring a
relatively large holding current or the second solenoid 12a requiring a
relatively small holding current. During initial energization of the
solenoid 12 or 12a, the detector 40 detects whether the relatively large
initial energization current 16 (FIG. 2) or the relatively small initial
energization current 22 is conducted to the solenoid. The identity of the
solenoid as being either the first solenoid 12 or the second solenoid 12a
is maintained by a detector latch 58 (FIG. 1).
The astable multivibrator 52 varies its output voltage so as to have either
a low duty output cycle or a high duty output cycle. When the detector 40
detects that the solenoid is the first solenoid 12 requiring a relatively
large holding current 20, the astable multivibrator 52 has a low duty
output cycle during the holding current time period, indicated at 34 in
FIG. 2. When the detector 40 (FIG. 1) detects that the solenoid is the
second solenoid 12a requiring a relatively small holding current 26, the
astable multivibrator 52 has a high duty output cycle during the holding
current time period, indicated by the arrow 34 in FIG. 2.
When the astable multivibrator 52 has a low duty output cycle, the output
voltage from the multivibrator is low for a relatively large portion of
the time 34 during which holding current is applied to the solenoid. The
relatively small resistance of the first solenoid 12 requiring the large
holding current enables the low duty output cycle to supply the required
holding current of approximately 1.0 amps. When the astable multivibrator
52 has a high duty output cycle, the output voltage from the multivibrator
is high for a relatively large portion of the time 34 during which holding
current is applied to the solenoid. The relatively large resistance of the
second solenoid 12a requiring the relatively small holding current
necessitates using the high duty output cycle to supply the required
holding current of approximately 0.8 amps.
The H-bridge circuit 50 (FIG. 1) responds to the low duty output cycle of
the astable multivibrator 52 to provide the relatively large holding
current required by the first solenoid 12. Similarly, the H-bridge circuit
50 responds to the high duty output cycle of the astable multivibrator 52
to provide the relatively small holding current required by the second
solenoid 12a. When the output voltage from the astable multivibrator 52 is
high, the H-bridge circuit 50 conducts holding current for the solenoid 12
or 12a. When the output voltage from the astable multivibrator 52 is low,
the H-bridge circuit 50 interrupts the flow of holding current for the
solenoid 12 12a.
It should be understood that the astable multivibrator 52 and H-bridge
circuit 50 could be constructed so as to cooperate in a different manner.
For example, during energization of the solenoid 12 requiring a relatively
large holding current, the astable multivibrator 52 could have a high duty
output cycle. The astable multivibrator 52 would then have a low duty
output cycle during energization of the solenoid 12a requiring a
relatively small holding current.
During initial energization of the solenoid 12 or 12a, an overcurrent
sensor 62 (FIG. 1) detects the conducting of excessive current to the
solenoid due to a fault in the solenoid or other cause. An overcurrent
latch 64 maintains the output of the overcurrent sensor 62. In response to
the overcurrent sensor 62 detecting the presence of an excessive initial
energization current to the solenoid 12 or 12a, the one-shot multivibrator
53 and the astable multivibrator 52 are both reset to interrupt the
initial energization of the solenoid 12 connected with the output 44.
Therefore, only a portion of the initial energization current is applied
to the defective solenoid and holding current is not applied to the
defective solenoid. An overcurrent indicator 68 indicates when the
overcurrent sensor 62 detects excessive flow of current to a solenoid.
A DC voltage converter 70 is provided in association with the solenoid
control circuitry 10. The DC converter 70 converts a 42 volt main power
source to a 15 volt power source for control functions. The main power
source is controlled by the H-bridge circuit 50 to effect energization of
the solenoid 12. Of course, voltages other than these specific voltages
may be utilized if desired.
Solenoid Control Circuitry
The solenoid control circuitry 10 (FIGS. 3A and 3B) has a pair of output
terminals 76 and 78 (FIG. 3B) at the output 44 to which the solenoid 12 is
connected. The output terminals 76 and 78 can be connected with either the
first solenoid 12 requiring a relatively large holding current or the
second solenoid 12a requiring a relatively small holding current. It
should be understood that only one of the two solenoids is connected with
the output terminals 76 and 78 at any given time.
The input 46 (FIG. 3A) receives an enable signal of approximately +5 V when
a solenoid 12 or 12a connected to the output terminals 76 and 78 is to be
actuated. The enable signal renders a transistor 82 (FIG. 3A) conducting
to render a current flow control transistor 84 (FIG. 3B) in the bridge
circuit 50 conducting. When the transistor 84 is conducting, power (+42 V)
is connected to output terminal 78 and the solenoid 12 or 12a. However, at
this instant, a MOSFET 86 is in a nonconducting condition and the solenoid
12 or 12a remains de-energized.
The enable signal is transmitted from the input 46 to the transistor 84
through the enable indicator 48 (FIG. 3A). The enable signal energizes a
light emitting diode 90 in the enable indicator 48. The diode 90 indicates
when an enable signal is being provided at the input 46 to the solenoid
control circuitry 10.
The enable signal is conducted from the input 46 to the base of a
transistor 92 (FIG. 3A) to render the transistor conducting. This results
in a low going input to an inverter 94. The high going output of the
inverter 94 is transmitted to an inverter 96. The low going output from
the inverter 96 is conducted to a trigger or input terminal 98 (FIG. 3B)
of the one-shot multivibrator 53. The low going output signal from the
inverter 96 is also conducted to an inverter 102. The resulting high going
output signal is conducted to a reset terminal 104 of the astable
multivibrator 52.
The input signal to the one-shot multivibrator 53 causes an output signal
conducted from an output terminal 106 (FIG. 3B) of the astable
multivibrator 52 to go high. The output signal from the terminal 106 of
the astable multivibrator 52 remains high for a period of time determined
by the characteristics of the one-shot multivibrator 53.
The one-shot multivibrator 53 forces the output at the terminal 106 of the
astable multivibrator 52 to remain high for a period of time which
corresponds to the initial energization period, indicated by the arrow 32
in FIG. 2. Thus, in the specific embodiment previously mentioned, the
output at the terminal 106 (FIG. 3B) of the astable multivibrator 52
remains high for an initial energization time period 32 (FIG. 2) having a
duration of approximately 27 milliseconds. Since the duration of the
initial energization time period 32 of the solenoid 12 is determined by
the one-shot multivibrator 53, the duration of the initial energization
time period is the same (27 milliseconds) for the first solenoid requiring
a relatively large holding current and the second solenoid requiring a
relatively small holding current. Of course, the one-shot multivibrator 53
may be constructed so as to provide a different initial energization time
period.
The high output signal of the astable multivibrator 52 is amplified by the
push-pull amplifier 54 and is conducted to the gate of a MOSFET 86 in the
H-bridge circuit 50. The high signal at the gate of the MOSFET 86 renders
the MOSFET conducting to energize the solenoid 12. The MOSFET 86 remains
conducting for the initial energization period during which the output at
the terminal 106 of the astable multivibrator 52 remains high.
If the solenoid connected with the output terminals 76 and 78 of the
solenoid control circuitry 10 is the first solenoid 12 which requires a
relatively large holding current, a relatively large initial energization
current 16 (FIG. 2) will be conducted from the transistor 84 (FIG. 3B)
through the solenoid to the MOSFET 86. If the solenoid connected with the
terminals 76 and 78 is the second solenoid 12a which requires a relatively
small holding current, a relatively small initial energization current 22
(FIG. 2) will be conducted from the transistor 84 (FIG. 3B) through the
solenoid to the MOSFET 86.
The detector 40 (FIG. 3A) detects whether there is a large or a small
voltage drop across a sensor resistor 112 (FIG. 3B) in the H-bridge
circuit 50. Thus, if the first solenoid which has a relatively small
resistance and which requires a relatively large initial energization
current and a relatively large holding current is connected with the
terminals 76 and 78, the relatively large initial energization current
will result in a relatively large voltage drop across the sensor resistor
112. However, if the second solenoid which has a relatively large
resistance and which requires a relatively small initial energization
current and a relatively small holding current is connected with the
terminals 76 and 78, the relatively small initial energization current
will result in a relatively small voltage drop across the sensor resistor
112.
A lead 114 conducts the voltage drop across the sensor resistor 112 to the
input of an amplifier 116 (FIG. 3A) in the detector 40. The amplifier 116
compares the voltage signal conducted over the lead 114 to a preselected
voltage. If the voltage drop across the sensor resistor 112 is relatively
large, indicating that the first solenoid requiring a relatively large
holding current is connected with the terminals 76 and 78, the output from
the amplifier 116 will change from a low signal to a high signal. However,
if the voltage conducted to the amplifier 116 over the lead 114 is
relatively small, indicating that the second solenoid requiring a
relatively small holding current is connected with the terminals 76 and
78, the output from the amplifier 116 will remain low.
The output from the detector latch 58 (FIG. 3A) is high when the output
from the detector 40 is high and is low when the output from the detector
40 is low. However, the detector latch 58 maintains a high or low output
after the initial energization period for the solenoid 12. Therefore, if
the first solenoid requiring a relatively large holding current is
connected with the output terminals 76 and 78, the detector latch 58 will
maintain a high output. If the second solenoid requiring a relatively
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