CA1297526C - Solenoid response detector - Google Patents
Solenoid response detectorInfo
- Publication number
- CA1297526C CA1297526C CA000613692A CA613692A CA1297526C CA 1297526 C CA1297526 C CA 1297526C CA 000613692 A CA000613692 A CA 000613692A CA 613692 A CA613692 A CA 613692A CA 1297526 C CA1297526 C CA 1297526C
- Authority
- CA
- Canada
- Prior art keywords
- armature
- time
- current flow
- counter
- solenoid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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- Magnetically Actuated Valves (AREA)
- Testing Electric Properties And Detecting Electric Faults (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method of and apparatus for energizing the coil of, and detecting the resultant armature actuation in, a solenoid of the type having a movable armature reciprocable along an axis between first and second positions, a spring bias normally biasing the armature toward the first position, and an actuating coil for inducing a force on the armature tending to move the armature from the first position toward the second position in response to current flow in the actuating coil. A voltage is first provided to the solenoid coil and thereafter, the resulting current flow in the solenoid coil is sensed. The sensed current flow is differentiated and a zero crossing comparator is utilized to determine when the differentiated current is zero and, therefor, the time at which the sensed current flow reaches a maximum (dv/dt=0). The time at which the armature began to move in response to the resulting coil current may be inferred and the voltage to the solenoid coiled interrupted a predetermined time after the time at which the armature began to move.
A method of and apparatus for energizing the coil of, and detecting the resultant armature actuation in, a solenoid of the type having a movable armature reciprocable along an axis between first and second positions, a spring bias normally biasing the armature toward the first position, and an actuating coil for inducing a force on the armature tending to move the armature from the first position toward the second position in response to current flow in the actuating coil. A voltage is first provided to the solenoid coil and thereafter, the resulting current flow in the solenoid coil is sensed. The sensed current flow is differentiated and a zero crossing comparator is utilized to determine when the differentiated current is zero and, therefor, the time at which the sensed current flow reaches a maximum (dv/dt=0). The time at which the armature began to move in response to the resulting coil current may be inferred and the voltage to the solenoid coiled interrupted a predetermined time after the time at which the armature began to move.
Description
12~75Z~
SOLENOID RESPONSE DETECTOR
SUMMARY OF T~IE INVENTION
The present invention relates ~enerally to an arr~ngemer.t for detecting actuation of a solenoid and more particularly to such an arrangement for sensing solenoid armature movement in a solenoid actuated valve.
Such solenoids are typically of the type having an actuating coil, a movable armature rsciprocable along an axis between first and second positions corresponding to valve-closed and valve-open positions respectively. A
spring or other means normally biases the armature toward the first position, with the actuating coil inducing a force on the armature tending to move the armature from the first position toward the second position in response to current flow in the actuating coil.
~n illustrative preferred environment of the present invention is in the control of electrohydraulic actuators of the doser type, for example, as disclosed in U.S. Patent No. 4,256,017 to Eastman. Briefly, when a measured quantity or "dose" of hydraulic fluid is injected into or exhausted from the control chamber of a differential area piston actuator, the piston motion or output is a step movement commensurate with the size of the input dose. The dose may be controlled by controlling the time duration of an enabling pulse to a solenoid actuated valve. The smallest discrete movements of the piston and, therefor, also the minimal or "quantum" dose will occur for the shortest effective actuation interval of the solenoid.
For precision positioning of a doser actuator, it is highly desirable to accurately deliver pulses which are of only slightly greater duration than the minimum threshold pulse of for given solenoid valve. Such a minimal duration pulse will be of sufficient duration to ensure that the valve moves from the normally closed position fully to the open position under all expected operating conditions while a pulse of lesser duration may not be sufficient to ensure full opening of the valve.
S2~i Doser control circuits are well known. For example, U.S. Patent 4,366,743 disclosed a circuit which supplies a pulse of slightly shorter duration than the anticipated threshold pulse and the incrementally increases the pulse width each time the controller senses that the solenoid threshold has not been exceeded. Since several increments are usually required, this approach is inherently slow and has significant time lag problems. The use of proportional incrementation calculations in systems similar to the patented device have increased the costs of such systems and only partially alleviated the time lag problem.
Among the several features of the present invention may be noted the provision of a simple and inexpensive solenoid actuation detector; the provision of such a detector which is easily retrofitted to existing solenoid control loops; the provision of a circuit for providing a pulse to a solenoid controlled, in part, by detection of the actuation of that solenoid; the elimination of mechanical switches, scheduling circuits, or pulse incrementation logic circuitry typical of prior solenoid movement sensors; the provision of a solenoid actuation detector having very rapid response characteristics and reduced sensitivity to loading effects;
and the provision of a simplistic yet effective solenoid response detector suitable for doser threshold detection applications. These as well as other advanta~eous features of the present invention will be in part apparent and in part pointed out hereinafter.
Specifically, the invention relates to a pulse width control circuit for energizing a solenoid having a moveable rn/
~75;2fi armature reciprocable along an axis between first and second positions, biasing means for urging the armature toward the first position and an actuating coil responsive to current flow for inducing a force on the armature to overcome the biasing means to move the armature from the first position toward the second position, the pulse width control circuit comprising: means for initiating current flow in the actuating coil; means for sensing current flow to the actuating coil; a resistance-capacitance circuit for differentiating sensed current flow to the actuating coil; comparator means for identifying the time at which the differentiated current is zero; a variable direct current biasing circuit coupled to the comparator means for shifting the differentiated current thereby changing the time at which the differentiated current is identified as being zero to provide an estimate of the departure time of the armature from the first position; a counter; a source of timing pulses coupled to the counter;
means for loading an initial count indicative of a predetermined time into the counter; means initiating timed counter operation at the estimated departure time to modify the initial count as a function of time; and counter responsive circuit means operable upon the count in the counter reaching a predetermined final count and thereafter terminating current flow to the actuating coil a predetermined time after initial armature movement away from the first position.
In general and in one form of the invention, the pulse width control circuit for a solenoid includes an arrangement for initiating current flow in the solenoid actuating coil rn/~
3a along with circuitry for determining the arrival time at which the armature arrives at the second or valve open position.
This arrival time may then be used to estimate the departure time of initial armature movement away from the first position. Current flow in the actuating coil is then terminated a predetermined time after initial armature movement away from the first position. The circuitry for determining arrival time may include a small resistor for sensing actuating coil current flow, a resistance-capacitance lo circuit for differentiating the sensed actuating coiled current flow, and a comparator for identifying the time at which the differentiated current is zero. Utilizing the arrival time to estimate the departure time may be accomplished by a variable direct current biasing circuit coupled to the comparator for shifting the time at which the differentiated current is identified as being zero. The circuitry for terminating actuating coil current flow includes a source of timing pulses, a decrementable counter, control circuitry for loading a number indicative of the predetermined time into the counter and for initiating counter decrementation at the estimated departure time, and a counter responsive circuit which is operable upon the count in the counter reaching zero for interrupting the current flow in the actuating coil. There may be a plurality of counter responsive circuits with the pulse width control circuit being shared by a like plurality of solenoids. The counter responsive circuit and the arrangement for initiating current flow rn/
1297~2~i may share at least one common circuit element such as a silicon controlled rectifier or similar on/off switching device.
~RIEF D~ CRIPTION OF THE DRAWINGS
Figure 1 is a schematic diagram of an electrical circuit suitable for the practice of the present invention;
Figure 2 is a collection of voltage or current waveforms on a common time scale at various points within the circuit of Figure l;
Figure 3 is an enlarged view of a typical solenoid current waveform; and Figure 4 is a waveform illustrating the effect of variation of the bias in the circuit of Figure 1.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawing.
The exemplifications set out herein illustrate a preferred embodiment of the invention in one form thereof and such exemplifications are not to be construed as limiting the scope of the disclosure or the scope of the invention in any manner.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring first to Figure 3 wherein the current flow in the coil of an illustrative solenoid i9 depicted, when a step voltage is applied at time T0 the coil of the solenoid, the current in the coil begins to in~rease along the familiar exponentially increasing waveform 11 with time constant L/R. If the solenoid armature fails to move, the time constant is unchanged and the current continues to increase to a steady state value along this same exponential curve, i.e., along the curve port~on 13.
However, if the solenoid armature begins to move at time Tl in response to the current in the coil, the inductance of the coil is changed to a new not necessarily constant value L' by this armature movement and the current deviates to follow a new generally exponentially increasing curve 15 with the new time constant L'/~. When the armature comes to rest at time T2 in its new (valve 1~97~
open) position, the inductance reverts to a constant value near the original value L, but there is a temporary back EMF generated in the coil which opposes the applied voltage and actually results in a temporary decrease in coil current as along the curve portion 17. Thereafter, at time T3, the current again increases exponentially with the original L/R time constant along curve segment l9. If the applied voltage is a pulse rather than a step of voltage, a somewhat similar decay of the coil current occurs upon the termination of the applied voltage.
Waveform A in Figure 2 is a waveform of the voltage aCross a small current monitoring resistor 21 in the circuit of Figure l ~hich accurately de~icts the current flow in one of the solenoid coils 35 or 37. Comparing Figures 2 and 3, the time interval between T0 and T2 represents the time required for the solenoid to operate after the voltage is applied, i.e., the opening delay. In the event the armature bounces or rebounds from its open or actuated position as is frequently the case, it will be repeatedly driven back toward that open position by the magnetic field generated by coil current and there will be a series of repetitions of the sequency of events occurring after T3 in Figure 3. A number of such rebounds or bounces are seen just subsequent to T3 in waveform A of Figure 2 before the coil current reaches its steady state value. The coil voltage pulse terminates at T4 and the armature returns to its initial position at T5. Coil current decay follows the same sequency of events as described in conjunction with Figure 3. Armature bounce and the resulting oscillations may occur upon deenergization, or depending on armature damping, the restorative force and other design parameters, no oscillation may appear. The solenoid closing delay for the particular illustrative solenoid is greater than the opening delay and no oscillations on closing are depicted in Figure 2.
7S2~i In the circuit of Figure 1, a small resistance 21, such as one ohm, is inserted in series with the supply and return solenoids. The current in the operating solenoid may then be monitored by sensing the voltage drop (shown in Figure 1, waveform A) across this resistor 21.
To approximate the point at which solenoid armature movement begins, the point at which the first oscillation occurs is determined by capacitor 23 and resistor 25 which differentiate the voltage across resistor 21 (Figure 2, waveform A). This differentiated voltage is depicted as waveform E in Figure 2 where each zero crossing or time when dv/dt=0 corresponds to a peak (maximum or minimum) of the solenoid coil current.
Waveform E is illustrated in somewhat exaggerated form in Figure 4. The first such zero crossing occurs at the time T2 when the armature reaches its full stroke, but may be used employing the variable bias adjustment potentiometer 27 to estimate the time Tl at which the armature begins to move. When potentiometer 27 is set so that the voltage on line 41 is the same as on line 39, comparator 29 is unbiased and zero crossing occurs at T2 in Figure ~. An increase in the setting of potentiometer 27 raises the zero voltage line in Figure 4 upwardly as, for example, to line 45 thereby also indicating an earlier zero crossing at Tl. The difference between Tl and T2 is preferably on the order of 30 microseconds.
~ omparator 29, which may be a type LM 319 with the pin number connections shown within the triangle, functions to compare the voltages on lines 31 and 33, and to provide an output signal in the form of a change in the output voltage level (waveform C) on line 36 upon the occurrence of each zero crossing, that is, when the two input voltages on lines 31 and 33 are the same. The 12 volt solenoid power supply on line 43 is utilized to operate the comparator 29 and a 5 volt low impedance reference with respect to the 12 volt return on line 45 is provided by a 5 volt return on line 45 is provided by a 5 volt regulator such as a LM78L05. A 4N33 photo coupler 47 1~75~
provides electrical isolation between the high current transitions of the solenoid drivers (pins 1 and 2) and the logic circuitry connected to pins 4 and 5 thereof.
At the start of each sampling period, the pulse width necessary for delivery to the proper solenoid is calculated from a linear relationship (request minus position at each sampling time) and that solenoid is turned on by the solenoid driver circuit 53 enabling the corresponding silicon controlled rectifier 49 or 51. The enable flipflop 55, for example, a type 74LS109, is held in a reset state by applying an inverted carry signal (waveform B) to its reset input pin. The pulse width counter 57 dwells in the carry state until new pulse width data is loaded from the control computer 59 into the counter at which time the reset signal is removed from the flipflop 55. The next zero crossing level change on line 36 will set the flipflop (signal C') to its high state and an output (waveform D) will enable the counter 57 to count up from the preloaded count and when the counter reaches the carry state, solenoid driver 53 disables the corresponding silicon controlled rectifier.
From the forgoing, it is now apparent that novel solenoid actuating and actuation detecting arrangements have been disclosed meeting the objects and advantageous features set out hereinbefore as well as others, and that numerous modifications as to the precise shapes, configurations and details may be made by those having ordinary skill in the art without departing from the spirit of the invention or the scope thereof as set out by the claims which follow.
' f
SOLENOID RESPONSE DETECTOR
SUMMARY OF T~IE INVENTION
The present invention relates ~enerally to an arr~ngemer.t for detecting actuation of a solenoid and more particularly to such an arrangement for sensing solenoid armature movement in a solenoid actuated valve.
Such solenoids are typically of the type having an actuating coil, a movable armature rsciprocable along an axis between first and second positions corresponding to valve-closed and valve-open positions respectively. A
spring or other means normally biases the armature toward the first position, with the actuating coil inducing a force on the armature tending to move the armature from the first position toward the second position in response to current flow in the actuating coil.
~n illustrative preferred environment of the present invention is in the control of electrohydraulic actuators of the doser type, for example, as disclosed in U.S. Patent No. 4,256,017 to Eastman. Briefly, when a measured quantity or "dose" of hydraulic fluid is injected into or exhausted from the control chamber of a differential area piston actuator, the piston motion or output is a step movement commensurate with the size of the input dose. The dose may be controlled by controlling the time duration of an enabling pulse to a solenoid actuated valve. The smallest discrete movements of the piston and, therefor, also the minimal or "quantum" dose will occur for the shortest effective actuation interval of the solenoid.
For precision positioning of a doser actuator, it is highly desirable to accurately deliver pulses which are of only slightly greater duration than the minimum threshold pulse of for given solenoid valve. Such a minimal duration pulse will be of sufficient duration to ensure that the valve moves from the normally closed position fully to the open position under all expected operating conditions while a pulse of lesser duration may not be sufficient to ensure full opening of the valve.
S2~i Doser control circuits are well known. For example, U.S. Patent 4,366,743 disclosed a circuit which supplies a pulse of slightly shorter duration than the anticipated threshold pulse and the incrementally increases the pulse width each time the controller senses that the solenoid threshold has not been exceeded. Since several increments are usually required, this approach is inherently slow and has significant time lag problems. The use of proportional incrementation calculations in systems similar to the patented device have increased the costs of such systems and only partially alleviated the time lag problem.
Among the several features of the present invention may be noted the provision of a simple and inexpensive solenoid actuation detector; the provision of such a detector which is easily retrofitted to existing solenoid control loops; the provision of a circuit for providing a pulse to a solenoid controlled, in part, by detection of the actuation of that solenoid; the elimination of mechanical switches, scheduling circuits, or pulse incrementation logic circuitry typical of prior solenoid movement sensors; the provision of a solenoid actuation detector having very rapid response characteristics and reduced sensitivity to loading effects;
and the provision of a simplistic yet effective solenoid response detector suitable for doser threshold detection applications. These as well as other advanta~eous features of the present invention will be in part apparent and in part pointed out hereinafter.
Specifically, the invention relates to a pulse width control circuit for energizing a solenoid having a moveable rn/
~75;2fi armature reciprocable along an axis between first and second positions, biasing means for urging the armature toward the first position and an actuating coil responsive to current flow for inducing a force on the armature to overcome the biasing means to move the armature from the first position toward the second position, the pulse width control circuit comprising: means for initiating current flow in the actuating coil; means for sensing current flow to the actuating coil; a resistance-capacitance circuit for differentiating sensed current flow to the actuating coil; comparator means for identifying the time at which the differentiated current is zero; a variable direct current biasing circuit coupled to the comparator means for shifting the differentiated current thereby changing the time at which the differentiated current is identified as being zero to provide an estimate of the departure time of the armature from the first position; a counter; a source of timing pulses coupled to the counter;
means for loading an initial count indicative of a predetermined time into the counter; means initiating timed counter operation at the estimated departure time to modify the initial count as a function of time; and counter responsive circuit means operable upon the count in the counter reaching a predetermined final count and thereafter terminating current flow to the actuating coil a predetermined time after initial armature movement away from the first position.
In general and in one form of the invention, the pulse width control circuit for a solenoid includes an arrangement for initiating current flow in the solenoid actuating coil rn/~
3a along with circuitry for determining the arrival time at which the armature arrives at the second or valve open position.
This arrival time may then be used to estimate the departure time of initial armature movement away from the first position. Current flow in the actuating coil is then terminated a predetermined time after initial armature movement away from the first position. The circuitry for determining arrival time may include a small resistor for sensing actuating coil current flow, a resistance-capacitance lo circuit for differentiating the sensed actuating coiled current flow, and a comparator for identifying the time at which the differentiated current is zero. Utilizing the arrival time to estimate the departure time may be accomplished by a variable direct current biasing circuit coupled to the comparator for shifting the time at which the differentiated current is identified as being zero. The circuitry for terminating actuating coil current flow includes a source of timing pulses, a decrementable counter, control circuitry for loading a number indicative of the predetermined time into the counter and for initiating counter decrementation at the estimated departure time, and a counter responsive circuit which is operable upon the count in the counter reaching zero for interrupting the current flow in the actuating coil. There may be a plurality of counter responsive circuits with the pulse width control circuit being shared by a like plurality of solenoids. The counter responsive circuit and the arrangement for initiating current flow rn/
1297~2~i may share at least one common circuit element such as a silicon controlled rectifier or similar on/off switching device.
~RIEF D~ CRIPTION OF THE DRAWINGS
Figure 1 is a schematic diagram of an electrical circuit suitable for the practice of the present invention;
Figure 2 is a collection of voltage or current waveforms on a common time scale at various points within the circuit of Figure l;
Figure 3 is an enlarged view of a typical solenoid current waveform; and Figure 4 is a waveform illustrating the effect of variation of the bias in the circuit of Figure 1.
Corresponding reference characters indicate corresponding parts throughout the several views of the drawing.
The exemplifications set out herein illustrate a preferred embodiment of the invention in one form thereof and such exemplifications are not to be construed as limiting the scope of the disclosure or the scope of the invention in any manner.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring first to Figure 3 wherein the current flow in the coil of an illustrative solenoid i9 depicted, when a step voltage is applied at time T0 the coil of the solenoid, the current in the coil begins to in~rease along the familiar exponentially increasing waveform 11 with time constant L/R. If the solenoid armature fails to move, the time constant is unchanged and the current continues to increase to a steady state value along this same exponential curve, i.e., along the curve port~on 13.
However, if the solenoid armature begins to move at time Tl in response to the current in the coil, the inductance of the coil is changed to a new not necessarily constant value L' by this armature movement and the current deviates to follow a new generally exponentially increasing curve 15 with the new time constant L'/~. When the armature comes to rest at time T2 in its new (valve 1~97~
open) position, the inductance reverts to a constant value near the original value L, but there is a temporary back EMF generated in the coil which opposes the applied voltage and actually results in a temporary decrease in coil current as along the curve portion 17. Thereafter, at time T3, the current again increases exponentially with the original L/R time constant along curve segment l9. If the applied voltage is a pulse rather than a step of voltage, a somewhat similar decay of the coil current occurs upon the termination of the applied voltage.
Waveform A in Figure 2 is a waveform of the voltage aCross a small current monitoring resistor 21 in the circuit of Figure l ~hich accurately de~icts the current flow in one of the solenoid coils 35 or 37. Comparing Figures 2 and 3, the time interval between T0 and T2 represents the time required for the solenoid to operate after the voltage is applied, i.e., the opening delay. In the event the armature bounces or rebounds from its open or actuated position as is frequently the case, it will be repeatedly driven back toward that open position by the magnetic field generated by coil current and there will be a series of repetitions of the sequency of events occurring after T3 in Figure 3. A number of such rebounds or bounces are seen just subsequent to T3 in waveform A of Figure 2 before the coil current reaches its steady state value. The coil voltage pulse terminates at T4 and the armature returns to its initial position at T5. Coil current decay follows the same sequency of events as described in conjunction with Figure 3. Armature bounce and the resulting oscillations may occur upon deenergization, or depending on armature damping, the restorative force and other design parameters, no oscillation may appear. The solenoid closing delay for the particular illustrative solenoid is greater than the opening delay and no oscillations on closing are depicted in Figure 2.
7S2~i In the circuit of Figure 1, a small resistance 21, such as one ohm, is inserted in series with the supply and return solenoids. The current in the operating solenoid may then be monitored by sensing the voltage drop (shown in Figure 1, waveform A) across this resistor 21.
To approximate the point at which solenoid armature movement begins, the point at which the first oscillation occurs is determined by capacitor 23 and resistor 25 which differentiate the voltage across resistor 21 (Figure 2, waveform A). This differentiated voltage is depicted as waveform E in Figure 2 where each zero crossing or time when dv/dt=0 corresponds to a peak (maximum or minimum) of the solenoid coil current.
Waveform E is illustrated in somewhat exaggerated form in Figure 4. The first such zero crossing occurs at the time T2 when the armature reaches its full stroke, but may be used employing the variable bias adjustment potentiometer 27 to estimate the time Tl at which the armature begins to move. When potentiometer 27 is set so that the voltage on line 41 is the same as on line 39, comparator 29 is unbiased and zero crossing occurs at T2 in Figure ~. An increase in the setting of potentiometer 27 raises the zero voltage line in Figure 4 upwardly as, for example, to line 45 thereby also indicating an earlier zero crossing at Tl. The difference between Tl and T2 is preferably on the order of 30 microseconds.
~ omparator 29, which may be a type LM 319 with the pin number connections shown within the triangle, functions to compare the voltages on lines 31 and 33, and to provide an output signal in the form of a change in the output voltage level (waveform C) on line 36 upon the occurrence of each zero crossing, that is, when the two input voltages on lines 31 and 33 are the same. The 12 volt solenoid power supply on line 43 is utilized to operate the comparator 29 and a 5 volt low impedance reference with respect to the 12 volt return on line 45 is provided by a 5 volt return on line 45 is provided by a 5 volt regulator such as a LM78L05. A 4N33 photo coupler 47 1~75~
provides electrical isolation between the high current transitions of the solenoid drivers (pins 1 and 2) and the logic circuitry connected to pins 4 and 5 thereof.
At the start of each sampling period, the pulse width necessary for delivery to the proper solenoid is calculated from a linear relationship (request minus position at each sampling time) and that solenoid is turned on by the solenoid driver circuit 53 enabling the corresponding silicon controlled rectifier 49 or 51. The enable flipflop 55, for example, a type 74LS109, is held in a reset state by applying an inverted carry signal (waveform B) to its reset input pin. The pulse width counter 57 dwells in the carry state until new pulse width data is loaded from the control computer 59 into the counter at which time the reset signal is removed from the flipflop 55. The next zero crossing level change on line 36 will set the flipflop (signal C') to its high state and an output (waveform D) will enable the counter 57 to count up from the preloaded count and when the counter reaches the carry state, solenoid driver 53 disables the corresponding silicon controlled rectifier.
From the forgoing, it is now apparent that novel solenoid actuating and actuation detecting arrangements have been disclosed meeting the objects and advantageous features set out hereinbefore as well as others, and that numerous modifications as to the precise shapes, configurations and details may be made by those having ordinary skill in the art without departing from the spirit of the invention or the scope thereof as set out by the claims which follow.
' f
Claims (3)
1. A pulse width control circuit for energizing a solenoid having a moveable armature reciprocable along an axis between first and second positions, biasing means for urging the armature toward the first position and an actuating coil responsive to current flow for inducing a force on the armature to overcome the biasing means to move the armature from the first position toward the second position, the pulse width control circuit comprising:
means for initiating current flow in the actuating coil;
means for sensing current flow to the actuating coil;
a resistance-capacitance circuit for differentiating sensed current flow to the actuating coil;
comparator means for identifying the time at which the differentiated current is zero;
a variable direct current biasing circuit coupled to the comparator means for shifting the differentiated current thereby changing the time at which the differentiated current is identified as being zero to provide an estimate of the departure time of the armature from the first position;
a counter;
a source of timing pulses coupled to said counter;
means for loading an initial count indicative of a predetermined time into said counter;
means initiating timed counter operation at the estimated departure time to modify the initial count as a function of time; and counter responsive circuit means operable upon the count in said counter reaching a predetermined final count and thereafter terminating current flow to the actuating coil a predetermined time after initial armature movement away from the first position.
means for initiating current flow in the actuating coil;
means for sensing current flow to the actuating coil;
a resistance-capacitance circuit for differentiating sensed current flow to the actuating coil;
comparator means for identifying the time at which the differentiated current is zero;
a variable direct current biasing circuit coupled to the comparator means for shifting the differentiated current thereby changing the time at which the differentiated current is identified as being zero to provide an estimate of the departure time of the armature from the first position;
a counter;
a source of timing pulses coupled to said counter;
means for loading an initial count indicative of a predetermined time into said counter;
means initiating timed counter operation at the estimated departure time to modify the initial count as a function of time; and counter responsive circuit means operable upon the count in said counter reaching a predetermined final count and thereafter terminating current flow to the actuating coil a predetermined time after initial armature movement away from the first position.
2. The pulse width control circuit of claim 1 wherein said counter responsive circuit means is connected to a plurality of solenoids.
3. The pulse width control circuit of claim 1 wherein the counter responsive circuit means and the means for initiating current flow share at least one common circuit element.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US36017489A | 1989-06-01 | 1989-06-01 | |
| US360,174 | 1989-06-01 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1297526C true CA1297526C (en) | 1992-03-17 |
Family
ID=23416886
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000613692A Expired - Lifetime CA1297526C (en) | 1989-06-01 | 1989-09-27 | Solenoid response detector |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH0313872A (en) |
| CA (1) | CA1297526C (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19529013C2 (en) | 1995-07-26 | 1999-09-30 | Siemens Ag | Method for testing the function of a mechanical switching element and device for carrying out the method |
| CN101937033B (en) * | 2010-07-23 | 2012-08-15 | 宁波市鄞州通力液压电器厂 | Automatic testing device of performance of electromagnet for valve |
-
1989
- 1989-09-27 CA CA000613692A patent/CA1297526C/en not_active Expired - Lifetime
-
1990
- 1990-03-14 JP JP6392990A patent/JPH0313872A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0313872A (en) | 1991-01-22 |
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