CA1096474A - Precision speed switch control - Google Patents
Precision speed switch controlInfo
- Publication number
- CA1096474A CA1096474A CA312,101A CA312101A CA1096474A CA 1096474 A CA1096474 A CA 1096474A CA 312101 A CA312101 A CA 312101A CA 1096474 A CA1096474 A CA 1096474A
- Authority
- CA
- Canada
- Prior art keywords
- circuit
- switch
- speed
- input
- signal
- 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
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
- G01P3/42—Devices characterised by the use of electric or magnetic means
- G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
- G01P3/46—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring amplitude of generated current or voltage
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
- H03K17/965—Switches controlled by moving an element forming part of the switch
- H03K17/97—Switches controlled by moving an element forming part of the switch using a magnetic movable element
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Control Of Eletrric Generators (AREA)
- Control Of Transmission Device (AREA)
- Keying Circuit Devices (AREA)
- Control Of Electric Motors In General (AREA)
- Control Of Velocity Or Acceleration (AREA)
- Electronic Switches (AREA)
- Control Of Direct Current Motors (AREA)
Abstract
S/Start 105 PRECISION SPEED SWITCH CONTROL
Abstract of the Disclosure A speed switch control comprising a subfractional permanent magnet AC generator generating an AC signal varying in amplitude with shaft speed variations; the AC signal is rectified and compared with a regulated DC reference to generate first and second threshold signals indicative of shaft speeds over and under a critical value. A switch actuator circuit develops "on" and "off" switch actuator signals, from the threshold signals to actuate a two-terminal solid state switch between on and off conditions; the "off"
signal is continuous but the "on" signal is a high-duty-cycle semi-continuous signal including brief recurring "off"
intervals. A power storage/supply circuit, connected in parallel with the switch terminals, which recharges during switch "off" intervals, affords the power supply for the threshold and switch actuator circuits.
Abstract of the Disclosure A speed switch control comprising a subfractional permanent magnet AC generator generating an AC signal varying in amplitude with shaft speed variations; the AC signal is rectified and compared with a regulated DC reference to generate first and second threshold signals indicative of shaft speeds over and under a critical value. A switch actuator circuit develops "on" and "off" switch actuator signals, from the threshold signals to actuate a two-terminal solid state switch between on and off conditions; the "off"
signal is continuous but the "on" signal is a high-duty-cycle semi-continuous signal including brief recurring "off"
intervals. A power storage/supply circuit, connected in parallel with the switch terminals, which recharges during switch "off" intervals, affords the power supply for the threshold and switch actuator circuits.
Description
7~
Lound of -the Invention There ar~ numerous applications in which i.t is necessary or desirable to control some safety interloc~ or other device in accordance with the speed of a rotati.ng shaft.
Vehicular applications are common; for example9 a control to latch or close the doors of a passenger vehicle whenever the vehicle is moving above a predetermined threshold speed, or an electrically actuated interlock me chanism to preclude shifting the transmission into reverse whenever the vehicle is moving :Eorward at even a limited threshold speed, or vice versa. Similar speed switch control needs, based upon the ro~ational speed of a shaft or like rotar~ men~er, are also commonly encountered in machine tools and other industrial equipment~
: The requirements imposed upon speed switch controls, .~ i, , particularly those employed in vehicular applications, are ,~
~requently quite severe. Thus, the control may be subjected to high levels of vibration and to substantial shock fQrces.
Electrical transients of substantial magnitude may be encountered. Because the control does not perform a primary operational function, it is.frequently subject to severe cost : limitations. In addition, it is highly desirable that the electrical connections to the control be as simple as possible, preferably constituting a simple two terminal connection,: to minimize cost and to facilitate replacement when necessary.
A variety of different speed switch controls have been devised for use in applications o-f this kind; many start with an input slgnal derived from a small AC gene.rator driven by the shaft or like rotary member being monitored~ The circui-ts of these devices have often been undesirable complex ~L~ 9 6 ~7 4 ancl costly particularly w}len oE~eration is based upon the fre-quency of the ~C lnput sign~ll r~quiring a Erequency~voltage conversion stage as a part of the control c:i~cu:i-tr~. The5e con-trols are difficult -to cons-truct in a form rugged enough for vehicular applications, in large part due to the circuit com-plexities introduced by frequency/voltage conversion. More~
over, many oE khese speed switch controls require three or more terminal connections. These problems are particularly acute in speed controls applied to vehicles. ' Inexpensive precision two-terminal speed switch con-trols are known. But those controls are not satisfactory for critical speeds below ten revolutions per minute where the output amplitude of the AC generator is quite small. This is particularly true in passenger vehicle safety control applica-tions, where a shaft speed of two rpm or even less may con-stitute the critical speed.
Moreover, a number of other important operating i; ~:
characteristics have been difficult and sometimes impossible to realize with previously known speed switch controls. Thus, it is highly desirable to provide a single basic speed switch control circuit that can be readily converted from operation as a normally open switch to operation as a normally closed switch, and vice versa, to meet the varying re~uirements of different safety devices and other loads. It is equally desirable to have a single basic speed switch control circuit that is capable of operation over a broad range of critical rotational speeds, from nearly zero rpm to hundreds of revolutions per minute, to minimize custom design of circuits to fit individual applications. Another critical requirement, in many applications, is the limination of "hunting" when the rotational speed of the irlput shaft is subject to substantial variation over a brief period of time. In addition a practical and effective precision speed swikch control should require dm/~
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only a ]ow power drain but: should be capahle of handling re-latively high currents, so that it can be ~a~lily adapted to a varie-ty of difEerent specific applications.
Summal-y~ the Invention __ _ _____ _ It is a principal object of the present invention, therefore, to provicle a new and improved solid sta-te electronic speecl switch control, utili~ing an input siynal from a sub-ractional permanent magnet AC generator driven by a rokating sha~t or like rotating member, that effectively overcomes or minimizes the problems and difficulties of previously known controls as described above.
A particular object of the invention is to provide a new and improved speed switch control for a rotary shaft, em-ploying simple solid state circuits that require only ~wo terminals for both load and power supply connections, that affords precision operation over a broad speed range extending down to speeds as low as one or two rpm~
Another specific object of the invention is to pro-vide a new and improved speed switch control that is readily convertible from operation as a normally open switch to oper ation as a normally closed switch, and vice versa, by a simple interchange of two circuit connections.
Another object of the invention is to provide a pre-cision speed switch control, having a broad range o~
.
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op~ratiny sp~ecls, that can be readily acljus-ted for di~ferent dropout delays, the dropout delay constituting the time interval between deceleration o~ an input sha:Et be:low a critical speed and the actual rev~rsion o:E the switch to an origi.nal operating condit.ion.
Accordingly, the invention relates to a two termi.nal precision speed switch control actuated by changes in the rotational speed of a shaft and adaptab:le to operation over a broad speed ranye down to less than ten rpm. The control comprises a sub-fractional AC generatorJ connectible to a rotary shaft, for generating an AC signal having an amplitude ~hic'.l ~alies wit~. changes in ~haft speed; a threshold ~.rcuit is connected to the generator and develops first and second threshold signals, one indicative of an AC signal input exceeding a given threshold amplitude corresponding to a critical shaft speed and the other indicative o~ an AC signai input below the threshold amplitude~ A switch actuator circuit is coupled to the threshold circuit~ for developing ON and OFF switch actuation signals corresponding to the first and second threshold signals, the o~ signal being a continuous DC signal of high duty cycle including brief recurring OFF
intervals. A solid-state switching circuit, having two switch terminals connectible in series wi-th an e~ternal power supply in an operating circuit for a controlled load, has its actuation input connected to the switch actuator circuit, actuatable to anilon~lcondition in which the impedance across the switch terminals is ~er~ low, in response to the ON switch actuation signal, and actuatable to an "o~"condition in which the impedance across the switch terminals is very high, in response to the OFF switch actuation signal~ A power storage/
supply circuit, is connected in parall~l wi~h the switch terminals, af~o:rcling a power supply :Eor the khreshold circuit and the swi.tch actua-tor clrcuit, and includirlg a storage d~vice which is re-chaxged during intervals in which the switching circuit is in its l'off" condition.
Bri.ef De.scription o~ the Drawings Fig. 1 is a simplified bl.ock diagram illustrating some of the principles of the present invention;
FigO 2 is a schematic circuit diagram for a speed switch control constructed in accordance with one embodiment ~ t;la present in~ention, Fig. 3 is a schematic circuit diagram illustrating a speed switch control constructed in accordance with another embodi.ment of the invantion;
~ FigO 4 illustrates certain operating characterist~s of the speed switch control circuits of Figs. 2 and 3; and Fig. 5 illustrates the peak-to-pea~ outpu~ of an AC generator used as the input device for the speed switch controls of Figs~ 1-3.
Description of the Preferred Embodiments FigO 1 provides a block diagram of a precision speed switch control 10 which incorporates some of the principles of the present invention. Control 10 comprises a multi-pole sub-fractional permanent magnet AC generator 11 having an input shaft 19~ In a given application, by way of example, shaft 19 may be driven from the speedometer cable, the drive shaft, or some operating element in the transmission ~ . . . . .
3~
of a vehi.cle. On the ol~ r hand, shaf-t ].9 may also be driven from the operati.n~ s~la:Et of: d macl~ine tool or o~her :inclusl:ria:L
machine that must be moni.tored for a safety function or o-ther control purpose. The preerred cons-truction Eor ~enerator 11 is th~ sixty pole perm~nent rnagnet AC generator disclosecl and claimed in U. S. Patent No. 4,074,157.
The output of the ~C generator 11 is electrically connected to a threshold circuit 12 that rectifies the AC
input and that develops an output comprising two different threshold signals. A first -threshold signal is generated by circuit 12 in response to an AC signal input below a given ~.
threshold amplitude corresponding to a critical speed for shaft 19. The second threshold signal output from circuit 12 indicates an AC signal in~ut corresponding to a sha~-t speed exceeding the critical speed. The output from threshold cir-cuit 12 is supplied to a switch actuator circuit 21.
Actuator c.ircuit 21 develops QFF and ON switch actuation signals corresponding to the first and second threshold signals from circuit 12. These switch actuation signals are in turn applied to a solid state switching circuit 13. Circuit 13 has two s~itch terminals 14 and 15, shown as connected to a pair of normally open switch contacts 16. Con-tacts 16 are included in Fig. 1 merely for purposes of illus-tration; the solid state switch 13 actually does not include any mechanically actuatable contacts~ but uses a solid state circuit to perform an equivalent switching function. In fact, a mechanical switch would not be usable for contact 16, due to inertia in operation, as wil.1 he apparent from the oper-ational description set fo~th hereinafter.
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Switch termillal.s l'~ and 15 arc electrically connected in series wlth all external power suppl.y J.7 and a load 18. In a vehicular application, power supply 17 may comprise the vehiclc battery~ In an industrial application, a power supply circu.it energized from a local utility or other source may be employedO An internal power storage/supply circuit 22 is connectecl in parallel with the switch terminals 14 and 15 and affords a power supply for both the threshold circuit 12 and the switch actuator circuit 210 Load 18 is most requently an alarm, a safety interlock circuit, or some other sa:Eety deviceO For example, in a bus or other passenyer vehicle, load 18 may comprlse an electrically-actuated interlocX to close or at least to prevent opening of a door whenever the vehicle is moving above r some critical speed~ In some instances, that critical speed may be represented by a very low speed for shaft l9, such as one or two rpm. In another vehicular application, load : 18 may comprise an interlock to prevent shifting of the transmission of the vehicle into reverse gear when the vehicle is moving in a forward direction, or vice versa~ Again, the critical speed for shaft l9 at which the safaty device of load 18 must be operated may be quite 1OWD of courseO load 18 may also comprise a simple visual or audible alarm in either industrial or vehicular applications.
In the operation of the speed switch control lO
of Fig~ l, generator ll develops an initial AC signal having an amplitude generally representative of the rotat:ional speed of its shaft 19, The relationship between the amplitude of the output signal from generator 11 and the speed of shaft l9 is seldom truly linear, Moxe commonl.y, the peak-to-peak 9~474 output voltage oE gellera-tor 11 usually conforms to a characteristic sim:ilar to cuxve 51 in ~i.g. 5, with the voltacJe rising rapidly for low and moderate speeds and increasirly much more ~radually a-t higher speeds. However, over an initial speed ranye,in this instance ~rom about zero to n~arly 400 rpm, -the speed-voltage curve 51 is a close approximation to a linear relationship, so that the output amplitude of the AC signal :Erom generator 11 is ess~ntial.ly represenkative of the rotational speed of shaft 19.
The AC signal from generator 11 (Fig. 1~ is rectified in threshold circuit 12 and is utili2ed in that circuit to develop rirst and second thresilold si~naLs, one indicative of shaft speeds exceeding a critical level and the other indicative of shaft speeds below khat critical level.
These two threshold signals are supplied to switch actuator circuit 21, which develops o~ and OFF switch actuation signaIs corresponding to the first and second threshold signals, respectively, These o~ and OFF output signals are illustrated in FigO 4~ As shown therein, the OFF signal is a continuous DC signal, whereas the o~ signal is a semi-continuous DC
signal of high duty cycle including a number of recurring OFF
intervals. The o~ and OFF signals from actuator circuit 21 are applied to the solid state switching circuit 13.
When the O~'F actuator signal from circuit 21 is being supplied to switching.circuit 13, the switching circuit is actuated to an "off" condition in which the impedance across the switch terminals 14 and 15 is very high, comparable to an open condition for a set of mechanicaL switching contacts such as the contacts 16. For this high impedance "off"
condition of circuit 13, the power storage/supply circuit 22 7~ `;
is continuously chaxcJedO Circuit 22 supplies suitable operatin~ voltages to both thresho.Lcl circuit 12 ancl switch actuator circui~ 21. Pre:Eerably, the storage/supply ci.rcuit 22 incorporates a volta~e regulator to maintain a constan-t supply level to threshold circui~. 12 regardless o:E variations in the output vo:Ltage from the external power supply 17.
Whenever solid state switching circuit 13 is actuated to its "on" condition~ however, the impedance across its switch terminals 14 and 15 is very low, corresponding 10 essesltially to the operating condition for a mechanical switch with the switch contacts 16 closed. Because the storage/supply circuit 22 is connected in parallel with switch terminals 14 a and 15, it receives little or no power input from the external power supply 17 under these conditions. Consequently, . circuit 22 would shortly become ineffective if the switch "on"
condnition were maintained continuously for switching circuit 13 for any substantial period of time. This is the reason for the recurring OFF intervals in the switch actuating signal applied to circuit 13 from actuator circuit 21 for t~e "on"
20 condition of tha switching circuit. During these brief OFF
intervals (Fig. 4) a capacitor or other storage device in circuit 22 is recharged~ and this enables the circuit to provide a continuous power supply for threshold circuit 12 and actuator circuit 21.
Fig. 2 affords a schematic diagram of a speed switch control 30 corresponding to the control 10 illustrated in Fig5 1. In control 30~ a subfractional permanen-t magnet AC generator 11 driven from an external shaft 19 has one output terminal connected to system ground with the other 30 output terminal connec-ted through a rectifier diode Dl to 3~47~
the non-inverting input -terminal 36 o:E a fi.rs-t opcrational amplifier ~1 in a -threshold ci:rcuit 12A.. A vol-tage-recJulating Zener diode zl is connected from terminal 36 to system ground, in parallel with a resistor Rl and a capacitor Cl~
The inverting input 32 of ampl.ifier ~l is connected to a voltage divider comprising two re.sistors R2 and ~3.
Resistor R3 is returned to sys-tem ground. Resistor R2 is connected to an output line 33 from a power storage/supply circuit 22A. Powe.r supply connections are also provided for amplifier Al, from line 33 and to system ground~
The power storage/supply circuit 22A of speed swltch control 3~, ~ig. 2, comprises a resistor ~ co~lected in series from khe output line 33 to an input line 34 tha~
lS connected through a blocking diode D4 to switch terminal 14 of a solid state switching circuit 13A~ A Zener diode Z2 is connected from output line 33 to system g~ und. A storage capacitor C2 is connected from input line 34 to system groundO
The switch actuator circuit 2lA in the embodiment of Fig. 2 comprises an operational amplifler A2 having a power supply connection to output line 33 of circuit 22A and another power supply connection to system ground. The non-inverting input 35 of amplifier A2 is connected to the center terminal 35 of a voltage divider comprising two resistors R7 and R9. Resistor R7 is connected to the output of amplifier Al in threshold circuit 12A. Resistor R9 is returned to system ground~ A feedback resistor R8 is connected ~rom the output o~ amplifier A2 back to input 35~
The inverting input 38 of amplifier A2 is connec-ted to a capacitor C3 that is returned to system ground. There is also a feedback circuit from the output of amplifier A2 to input 38. Tl-lis is a parallel circuit comprising, in one branch, a resistor R6, arlcl in the othcr branch, the series combination o~ a rcsistor R5 ancl a cliode D5~
The solid state switching devlce 13A of speed switch control 30, Fig. 2, is a dual transistor Darlinyton ampli~ier~ The inpu-t to switch 13A comprises a series resistor R10 connected from the output of amplifier A2 in actuator circuit 2lA to the base of the ~irst transistor in the Darlington amplifier. The collector and emitter of the second transistor provide the switch terminals 14 and 15.
A transient protection cireuit, comprising a Zener diode Z3 and d parallel capaeitor C4, are connected from switch terminal 14 to the input of the Darlington amplifier.
The external eireuit connected to the speed switch eontrol 30 in Fig. 2 comprises a power supply 17 having its negative terminal connected to switch terminal 15, which is also connected to system ground. The positive terminal of power supply 17 is eonneeted to load 18, generally indicated as a load resistor RL, whieh is in turn eonnected to the other switeh terminal 14.
I~ eonsidering the operation of speed switch eontrol 30, it may first be assumed that the shaft l9 driving AC generator ll is not rotating so that there is no AC output signal from the generator. under these circumstances, -there is no eff~ctive signal at the input 36 of ampli~ier Al. The onl~ effeetive input to amplifier Al is a positive DC signal at the inverting input 32 of the amplifier. As a consequence, the oukput ~rom amplifier Al is held steady at about ground potential.
Th~ external circuit connected to the speed switch control 30 in FigO 2 comprises a power supply 17 haviny its nega-t:ive terminal connected to switch terminal 15, which is also connected to system ground. The posi-t.ive terminal of power supply 17 is connected to load 18, generally indi.cated as a load resistor RL, which is in turn connected to the other switch te.rminal 14.
In considering the operation of speed switch control 30, it may first be assumed that the shaft 19 driving ~C generator 11 is not rotating so that there is no AC output signal from the generator. Under these circumstances~ there is no ef~ecti~e si~nal at t.he input 36 of amplif-ar Al. The only e~fective input to amplifier Al is a positive DC signal at the invextlng input 32 of the amplifier. As a consequence, the output from amplifier Al is held steady at about ground potential.
Switch actuator circuit 21A is a conventional Schmitt trigger pulse generator, which requires a positive voltage at terminal 35 to produce an efective output signal.
Consequently, the output from amplifier A2 is at about system ground, affording the continuous OFF signal shown in Fig~ 4.
For this output from amplifier A2, the Darlington amplifier 13A is cut off, with both transistors non-conductive, so that there is a very high i.mpedance across switch terminals 14 and 15; the switch 13A is eEfectively openO With the switch open, capacitor C2 is charged from the external power supply 17. Zener diode z2 maintains a steady operating voltage on line 33, regardless of 1uctuations i.n the power supply 17 or the charge on capaci-tox C2.
I:E the shaf-t 19 driving generator 11 now begins to _ 13 -7~ ;
rotate~ a positive-pola.rity DC s:iynal, increasin~ in amplitude with increasinc-l speed, i.s cl~veloped in the i.nput. clrcuit connec-ting the AC generator to the non-invertiny input 36 oE
ampli:Eier ~1. As lon~ as -the voltage at terminal 36 remains below the voltage at terminal 32, there :is no essent.ial change in opexating conditions because the output from the differential amplifier Al remains at about ground potential.
It should be noted that the reference voltage at terminal 32 remains constan~ due to the effect of the voltaye regulatorO
circuit 22A.
When the rotational speed of generator 11 increases to a point at whicn the ~oita~e at terminal 36 e~ceeds tnat at terminal 32, the output from amplifier Al goes positive.
This provides a positive input to the non-inverting input 35 of amplifier A2. As a consequence, the monostable trigger circuit 21A produces a positive output signal corresponding to the o~ signal shown in Fig. 4, with recurring brief negative-going OFF intervals. Whenever the actuation signa~L from circuit 21A is positive, the switching circuit 13A is driven fully conductive, affording a very low impedance across the switch terminals 14 and 15 and energizing safety device 18 from power supply 17.
During the extended intervals that the switching circuit 13A is conductiver the charge on capacitor C2 maintains the requisite output voltage on line 33 to maintain amplifiers Al and A2 in operation. Moreover, the reference voltage at terminal 32 is also maintained constant. During the 'lon"
condition for control 30~ capacitor C2. is recharged during those brief intervals in which the switching device :L3A is cut off, by the OFF interval signals indicated in Fig. 4.
_ 14 ~
Thus, con-trol 30 can maintain operation in an "on" condition for an indefinite period. The duty cycle Eor switch actuator circuit 2l~, ancl hence Eor switching circuit 13A, can ~e maintained at a very high leval, usuall.y 95% or more.
Typ.ically, the pulse frequency for the OFF intervals, Fig 4, may be oE the oxder of 300 to 400 Hz, depending upon the circuit parameters and the voltage of power supply 17~ with the period Tl ranging from about 2.5 to 3~5 milliseconds and the interval duration T2 being of the order of 75 microseconds.
If gene.rator shaft l9 now slows down, below the critical speed for control 30, so that the voltage at terminal 36 ~;ops below tha voltaga at terminal 32, the o~.tput of amplifier Al again drops to about ground potential. As a consequence, the voltage at terminal 35 drops below the level necessary to sustain operation of the pulse generator circuit 2l~. The output of amplifier A2 drops to near system groun~
and switching device 13A is again cut off. However, this dropout action does not take place immediately when the generator slows to just below the critical speed. Instead~
there is some dropout delay, determined by resistor Rl and capacitor Cl.
During operation of speed switch control 30, Fig.
Lound of -the Invention There ar~ numerous applications in which i.t is necessary or desirable to control some safety interloc~ or other device in accordance with the speed of a rotati.ng shaft.
Vehicular applications are common; for example9 a control to latch or close the doors of a passenger vehicle whenever the vehicle is moving above a predetermined threshold speed, or an electrically actuated interlock me chanism to preclude shifting the transmission into reverse whenever the vehicle is moving :Eorward at even a limited threshold speed, or vice versa. Similar speed switch control needs, based upon the ro~ational speed of a shaft or like rotar~ men~er, are also commonly encountered in machine tools and other industrial equipment~
: The requirements imposed upon speed switch controls, .~ i, , particularly those employed in vehicular applications, are ,~
~requently quite severe. Thus, the control may be subjected to high levels of vibration and to substantial shock fQrces.
Electrical transients of substantial magnitude may be encountered. Because the control does not perform a primary operational function, it is.frequently subject to severe cost : limitations. In addition, it is highly desirable that the electrical connections to the control be as simple as possible, preferably constituting a simple two terminal connection,: to minimize cost and to facilitate replacement when necessary.
A variety of different speed switch controls have been devised for use in applications o-f this kind; many start with an input slgnal derived from a small AC gene.rator driven by the shaft or like rotary member being monitored~ The circui-ts of these devices have often been undesirable complex ~L~ 9 6 ~7 4 ancl costly particularly w}len oE~eration is based upon the fre-quency of the ~C lnput sign~ll r~quiring a Erequency~voltage conversion stage as a part of the control c:i~cu:i-tr~. The5e con-trols are difficult -to cons-truct in a form rugged enough for vehicular applications, in large part due to the circuit com-plexities introduced by frequency/voltage conversion. More~
over, many oE khese speed switch controls require three or more terminal connections. These problems are particularly acute in speed controls applied to vehicles. ' Inexpensive precision two-terminal speed switch con-trols are known. But those controls are not satisfactory for critical speeds below ten revolutions per minute where the output amplitude of the AC generator is quite small. This is particularly true in passenger vehicle safety control applica-tions, where a shaft speed of two rpm or even less may con-stitute the critical speed.
Moreover, a number of other important operating i; ~:
characteristics have been difficult and sometimes impossible to realize with previously known speed switch controls. Thus, it is highly desirable to provide a single basic speed switch control circuit that can be readily converted from operation as a normally open switch to operation as a normally closed switch, and vice versa, to meet the varying re~uirements of different safety devices and other loads. It is equally desirable to have a single basic speed switch control circuit that is capable of operation over a broad range of critical rotational speeds, from nearly zero rpm to hundreds of revolutions per minute, to minimize custom design of circuits to fit individual applications. Another critical requirement, in many applications, is the limination of "hunting" when the rotational speed of the irlput shaft is subject to substantial variation over a brief period of time. In addition a practical and effective precision speed swikch control should require dm/~
6~
only a ]ow power drain but: should be capahle of handling re-latively high currents, so that it can be ~a~lily adapted to a varie-ty of difEerent specific applications.
Summal-y~ the Invention __ _ _____ _ It is a principal object of the present invention, therefore, to provicle a new and improved solid sta-te electronic speecl switch control, utili~ing an input siynal from a sub-ractional permanent magnet AC generator driven by a rokating sha~t or like rotating member, that effectively overcomes or minimizes the problems and difficulties of previously known controls as described above.
A particular object of the invention is to provide a new and improved speed switch control for a rotary shaft, em-ploying simple solid state circuits that require only ~wo terminals for both load and power supply connections, that affords precision operation over a broad speed range extending down to speeds as low as one or two rpm~
Another specific object of the invention is to pro-vide a new and improved speed switch control that is readily convertible from operation as a normally open switch to oper ation as a normally closed switch, and vice versa, by a simple interchange of two circuit connections.
Another object of the invention is to provide a pre-cision speed switch control, having a broad range o~
.
dm~
:
i47~
op~ratiny sp~ecls, that can be readily acljus-ted for di~ferent dropout delays, the dropout delay constituting the time interval between deceleration o~ an input sha:Et be:low a critical speed and the actual rev~rsion o:E the switch to an origi.nal operating condit.ion.
Accordingly, the invention relates to a two termi.nal precision speed switch control actuated by changes in the rotational speed of a shaft and adaptab:le to operation over a broad speed ranye down to less than ten rpm. The control comprises a sub-fractional AC generatorJ connectible to a rotary shaft, for generating an AC signal having an amplitude ~hic'.l ~alies wit~. changes in ~haft speed; a threshold ~.rcuit is connected to the generator and develops first and second threshold signals, one indicative of an AC signal input exceeding a given threshold amplitude corresponding to a critical shaft speed and the other indicative o~ an AC signai input below the threshold amplitude~ A switch actuator circuit is coupled to the threshold circuit~ for developing ON and OFF switch actuation signals corresponding to the first and second threshold signals, the o~ signal being a continuous DC signal of high duty cycle including brief recurring OFF
intervals. A solid-state switching circuit, having two switch terminals connectible in series wi-th an e~ternal power supply in an operating circuit for a controlled load, has its actuation input connected to the switch actuator circuit, actuatable to anilon~lcondition in which the impedance across the switch terminals is ~er~ low, in response to the ON switch actuation signal, and actuatable to an "o~"condition in which the impedance across the switch terminals is very high, in response to the OFF switch actuation signal~ A power storage/
supply circuit, is connected in parall~l wi~h the switch terminals, af~o:rcling a power supply :Eor the khreshold circuit and the swi.tch actua-tor clrcuit, and includirlg a storage d~vice which is re-chaxged during intervals in which the switching circuit is in its l'off" condition.
Bri.ef De.scription o~ the Drawings Fig. 1 is a simplified bl.ock diagram illustrating some of the principles of the present invention;
FigO 2 is a schematic circuit diagram for a speed switch control constructed in accordance with one embodiment ~ t;la present in~ention, Fig. 3 is a schematic circuit diagram illustrating a speed switch control constructed in accordance with another embodi.ment of the invantion;
~ FigO 4 illustrates certain operating characterist~s of the speed switch control circuits of Figs. 2 and 3; and Fig. 5 illustrates the peak-to-pea~ outpu~ of an AC generator used as the input device for the speed switch controls of Figs~ 1-3.
Description of the Preferred Embodiments FigO 1 provides a block diagram of a precision speed switch control 10 which incorporates some of the principles of the present invention. Control 10 comprises a multi-pole sub-fractional permanent magnet AC generator 11 having an input shaft 19~ In a given application, by way of example, shaft 19 may be driven from the speedometer cable, the drive shaft, or some operating element in the transmission ~ . . . . .
3~
of a vehi.cle. On the ol~ r hand, shaf-t ].9 may also be driven from the operati.n~ s~la:Et of: d macl~ine tool or o~her :inclusl:ria:L
machine that must be moni.tored for a safety function or o-ther control purpose. The preerred cons-truction Eor ~enerator 11 is th~ sixty pole perm~nent rnagnet AC generator disclosecl and claimed in U. S. Patent No. 4,074,157.
The output of the ~C generator 11 is electrically connected to a threshold circuit 12 that rectifies the AC
input and that develops an output comprising two different threshold signals. A first -threshold signal is generated by circuit 12 in response to an AC signal input below a given ~.
threshold amplitude corresponding to a critical speed for shaft 19. The second threshold signal output from circuit 12 indicates an AC signal in~ut corresponding to a sha~-t speed exceeding the critical speed. The output from threshold cir-cuit 12 is supplied to a switch actuator circuit 21.
Actuator c.ircuit 21 develops QFF and ON switch actuation signals corresponding to the first and second threshold signals from circuit 12. These switch actuation signals are in turn applied to a solid state switching circuit 13. Circuit 13 has two s~itch terminals 14 and 15, shown as connected to a pair of normally open switch contacts 16. Con-tacts 16 are included in Fig. 1 merely for purposes of illus-tration; the solid state switch 13 actually does not include any mechanically actuatable contacts~ but uses a solid state circuit to perform an equivalent switching function. In fact, a mechanical switch would not be usable for contact 16, due to inertia in operation, as wil.1 he apparent from the oper-ational description set fo~th hereinafter.
dm/
~1)9~
Switch termillal.s l'~ and 15 arc electrically connected in series wlth all external power suppl.y J.7 and a load 18. In a vehicular application, power supply 17 may comprise the vehiclc battery~ In an industrial application, a power supply circu.it energized from a local utility or other source may be employedO An internal power storage/supply circuit 22 is connectecl in parallel with the switch terminals 14 and 15 and affords a power supply for both the threshold circuit 12 and the switch actuator circuit 210 Load 18 is most requently an alarm, a safety interlock circuit, or some other sa:Eety deviceO For example, in a bus or other passenyer vehicle, load 18 may comprlse an electrically-actuated interlocX to close or at least to prevent opening of a door whenever the vehicle is moving above r some critical speed~ In some instances, that critical speed may be represented by a very low speed for shaft l9, such as one or two rpm. In another vehicular application, load : 18 may comprise an interlock to prevent shifting of the transmission of the vehicle into reverse gear when the vehicle is moving in a forward direction, or vice versa~ Again, the critical speed for shaft l9 at which the safaty device of load 18 must be operated may be quite 1OWD of courseO load 18 may also comprise a simple visual or audible alarm in either industrial or vehicular applications.
In the operation of the speed switch control lO
of Fig~ l, generator ll develops an initial AC signal having an amplitude generally representative of the rotat:ional speed of its shaft 19, The relationship between the amplitude of the output signal from generator 11 and the speed of shaft l9 is seldom truly linear, Moxe commonl.y, the peak-to-peak 9~474 output voltage oE gellera-tor 11 usually conforms to a characteristic sim:ilar to cuxve 51 in ~i.g. 5, with the voltacJe rising rapidly for low and moderate speeds and increasirly much more ~radually a-t higher speeds. However, over an initial speed ranye,in this instance ~rom about zero to n~arly 400 rpm, -the speed-voltage curve 51 is a close approximation to a linear relationship, so that the output amplitude of the AC signal :Erom generator 11 is ess~ntial.ly represenkative of the rotational speed of shaft 19.
The AC signal from generator 11 (Fig. 1~ is rectified in threshold circuit 12 and is utili2ed in that circuit to develop rirst and second thresilold si~naLs, one indicative of shaft speeds exceeding a critical level and the other indicative of shaft speeds below khat critical level.
These two threshold signals are supplied to switch actuator circuit 21, which develops o~ and OFF switch actuation signaIs corresponding to the first and second threshold signals, respectively, These o~ and OFF output signals are illustrated in FigO 4~ As shown therein, the OFF signal is a continuous DC signal, whereas the o~ signal is a semi-continuous DC
signal of high duty cycle including a number of recurring OFF
intervals. The o~ and OFF signals from actuator circuit 21 are applied to the solid state switching circuit 13.
When the O~'F actuator signal from circuit 21 is being supplied to switching.circuit 13, the switching circuit is actuated to an "off" condition in which the impedance across the switch terminals 14 and 15 is very high, comparable to an open condition for a set of mechanicaL switching contacts such as the contacts 16. For this high impedance "off"
condition of circuit 13, the power storage/supply circuit 22 7~ `;
is continuously chaxcJedO Circuit 22 supplies suitable operatin~ voltages to both thresho.Lcl circuit 12 ancl switch actuator circui~ 21. Pre:Eerably, the storage/supply ci.rcuit 22 incorporates a volta~e regulator to maintain a constan-t supply level to threshold circui~. 12 regardless o:E variations in the output vo:Ltage from the external power supply 17.
Whenever solid state switching circuit 13 is actuated to its "on" condition~ however, the impedance across its switch terminals 14 and 15 is very low, corresponding 10 essesltially to the operating condition for a mechanical switch with the switch contacts 16 closed. Because the storage/supply circuit 22 is connected in parallel with switch terminals 14 a and 15, it receives little or no power input from the external power supply 17 under these conditions. Consequently, . circuit 22 would shortly become ineffective if the switch "on"
condnition were maintained continuously for switching circuit 13 for any substantial period of time. This is the reason for the recurring OFF intervals in the switch actuating signal applied to circuit 13 from actuator circuit 21 for t~e "on"
20 condition of tha switching circuit. During these brief OFF
intervals (Fig. 4) a capacitor or other storage device in circuit 22 is recharged~ and this enables the circuit to provide a continuous power supply for threshold circuit 12 and actuator circuit 21.
Fig. 2 affords a schematic diagram of a speed switch control 30 corresponding to the control 10 illustrated in Fig5 1. In control 30~ a subfractional permanen-t magnet AC generator 11 driven from an external shaft 19 has one output terminal connected to system ground with the other 30 output terminal connec-ted through a rectifier diode Dl to 3~47~
the non-inverting input -terminal 36 o:E a fi.rs-t opcrational amplifier ~1 in a -threshold ci:rcuit 12A.. A vol-tage-recJulating Zener diode zl is connected from terminal 36 to system ground, in parallel with a resistor Rl and a capacitor Cl~
The inverting input 32 of ampl.ifier ~l is connected to a voltage divider comprising two re.sistors R2 and ~3.
Resistor R3 is returned to sys-tem ground. Resistor R2 is connected to an output line 33 from a power storage/supply circuit 22A. Powe.r supply connections are also provided for amplifier Al, from line 33 and to system ground~
The power storage/supply circuit 22A of speed swltch control 3~, ~ig. 2, comprises a resistor ~ co~lected in series from khe output line 33 to an input line 34 tha~
lS connected through a blocking diode D4 to switch terminal 14 of a solid state switching circuit 13A~ A Zener diode Z2 is connected from output line 33 to system g~ und. A storage capacitor C2 is connected from input line 34 to system groundO
The switch actuator circuit 2lA in the embodiment of Fig. 2 comprises an operational amplifler A2 having a power supply connection to output line 33 of circuit 22A and another power supply connection to system ground. The non-inverting input 35 of amplifier A2 is connected to the center terminal 35 of a voltage divider comprising two resistors R7 and R9. Resistor R7 is connected to the output of amplifier Al in threshold circuit 12A. Resistor R9 is returned to system ground~ A feedback resistor R8 is connected ~rom the output o~ amplifier A2 back to input 35~
The inverting input 38 of amplifier A2 is connec-ted to a capacitor C3 that is returned to system ground. There is also a feedback circuit from the output of amplifier A2 to input 38. Tl-lis is a parallel circuit comprising, in one branch, a resistor R6, arlcl in the othcr branch, the series combination o~ a rcsistor R5 ancl a cliode D5~
The solid state switching devlce 13A of speed switch control 30, Fig. 2, is a dual transistor Darlinyton ampli~ier~ The inpu-t to switch 13A comprises a series resistor R10 connected from the output of amplifier A2 in actuator circuit 2lA to the base of the ~irst transistor in the Darlington amplifier. The collector and emitter of the second transistor provide the switch terminals 14 and 15.
A transient protection cireuit, comprising a Zener diode Z3 and d parallel capaeitor C4, are connected from switch terminal 14 to the input of the Darlington amplifier.
The external eireuit connected to the speed switch eontrol 30 in Fig. 2 comprises a power supply 17 having its negative terminal connected to switch terminal 15, which is also connected to system ground. The positive terminal of power supply 17 is eonneeted to load 18, generally indicated as a load resistor RL, whieh is in turn eonnected to the other switeh terminal 14.
I~ eonsidering the operation of speed switch eontrol 30, it may first be assumed that the shaft l9 driving AC generator ll is not rotating so that there is no AC output signal from the generator. under these circumstances, -there is no eff~ctive signal at the input 36 of ampli~ier Al. The onl~ effeetive input to amplifier Al is a positive DC signal at the inverting input 32 of the amplifier. As a consequence, the oukput ~rom amplifier Al is held steady at about ground potential.
Th~ external circuit connected to the speed switch control 30 in FigO 2 comprises a power supply 17 haviny its nega-t:ive terminal connected to switch terminal 15, which is also connected to system ground. The posi-t.ive terminal of power supply 17 is connected to load 18, generally indi.cated as a load resistor RL, which is in turn connected to the other switch te.rminal 14.
In considering the operation of speed switch control 30, it may first be assumed that the shaft 19 driving ~C generator 11 is not rotating so that there is no AC output signal from the generator. Under these circumstances~ there is no ef~ecti~e si~nal at t.he input 36 of amplif-ar Al. The only e~fective input to amplifier Al is a positive DC signal at the invextlng input 32 of the amplifier. As a consequence, the output from amplifier Al is held steady at about ground potential.
Switch actuator circuit 21A is a conventional Schmitt trigger pulse generator, which requires a positive voltage at terminal 35 to produce an efective output signal.
Consequently, the output from amplifier A2 is at about system ground, affording the continuous OFF signal shown in Fig~ 4.
For this output from amplifier A2, the Darlington amplifier 13A is cut off, with both transistors non-conductive, so that there is a very high i.mpedance across switch terminals 14 and 15; the switch 13A is eEfectively openO With the switch open, capacitor C2 is charged from the external power supply 17. Zener diode z2 maintains a steady operating voltage on line 33, regardless of 1uctuations i.n the power supply 17 or the charge on capaci-tox C2.
I:E the shaf-t 19 driving generator 11 now begins to _ 13 -7~ ;
rotate~ a positive-pola.rity DC s:iynal, increasin~ in amplitude with increasinc-l speed, i.s cl~veloped in the i.nput. clrcuit connec-ting the AC generator to the non-invertiny input 36 oE
ampli:Eier ~1. As lon~ as -the voltage at terminal 36 remains below the voltage at terminal 32, there :is no essent.ial change in opexating conditions because the output from the differential amplifier Al remains at about ground potential.
It should be noted that the reference voltage at terminal 32 remains constan~ due to the effect of the voltaye regulatorO
circuit 22A.
When the rotational speed of generator 11 increases to a point at whicn the ~oita~e at terminal 36 e~ceeds tnat at terminal 32, the output from amplifier Al goes positive.
This provides a positive input to the non-inverting input 35 of amplifier A2. As a consequence, the monostable trigger circuit 21A produces a positive output signal corresponding to the o~ signal shown in Fig. 4, with recurring brief negative-going OFF intervals. Whenever the actuation signa~L from circuit 21A is positive, the switching circuit 13A is driven fully conductive, affording a very low impedance across the switch terminals 14 and 15 and energizing safety device 18 from power supply 17.
During the extended intervals that the switching circuit 13A is conductiver the charge on capacitor C2 maintains the requisite output voltage on line 33 to maintain amplifiers Al and A2 in operation. Moreover, the reference voltage at terminal 32 is also maintained constant. During the 'lon"
condition for control 30~ capacitor C2. is recharged during those brief intervals in which the switching device :L3A is cut off, by the OFF interval signals indicated in Fig. 4.
_ 14 ~
Thus, con-trol 30 can maintain operation in an "on" condition for an indefinite period. The duty cycle Eor switch actuator circuit 2l~, ancl hence Eor switching circuit 13A, can ~e maintained at a very high leval, usuall.y 95% or more.
Typ.ically, the pulse frequency for the OFF intervals, Fig 4, may be oE the oxder of 300 to 400 Hz, depending upon the circuit parameters and the voltage of power supply 17~ with the period Tl ranging from about 2.5 to 3~5 milliseconds and the interval duration T2 being of the order of 75 microseconds.
If gene.rator shaft l9 now slows down, below the critical speed for control 30, so that the voltage at terminal 36 ~;ops below tha voltaga at terminal 32, the o~.tput of amplifier Al again drops to about ground potential. As a consequence, the voltage at terminal 35 drops below the level necessary to sustain operation of the pulse generator circuit 2l~. The output of amplifier A2 drops to near system groun~
and switching device 13A is again cut off. However, this dropout action does not take place immediately when the generator slows to just below the critical speed. Instead~
there is some dropout delay, determined by resistor Rl and capacitor Cl.
During operation of speed switch control 30, Fig.
2, Zener diode Zl limits the input volta~ applied to amplifier Al from generator ll, through diode Dl, and prevents damage to the amplifier. This is necessary in many applications, since the output voltage from generator ll may reach relatively high values as shown in FigO 5~
The critical speed for generato.r ll that is utilized to determine whether control 30 maintains ;.ks switch 13A
"on" or "off" is determined by the ratio of resistors R2 - :
and R30 By chancJillg one oS- these resistors, a s~lbstan-tially dif:Eeren-t critical speecl can be e~t~bl:L~ ed. o:E cou:rse, a variable resistors coulcl be utilizecl if desi.redu On the other hand, to change -the control from a normally open swi-tch to a norma:lly c:Losed swi-tch, it is only necessary to inter change the input connec-tions ko amplifier Al. Thus~ if the connections for -terminals 32 and 36 of amplifier ~1 are reversed, control 30 will function as a normally closed switching device, with operation other~ise unchangea from that described above. By the same token, the dropout delay time during which the switch 13~ is maintained actuated after sha~t 19 of generator 11 falls below the critical speed can be readily adj.usted by changiny the resistor Rl or the capacitor Cl In order to afford a more complete and concrete example of a speed switch control constructed in accordance with the present invention and utilizing the circuit 30 of Fig. 2, specific parameters are set forth below in Table I.
With the values shown in Table I, speed switch control 30 functions as a normally open switch having a critical speed ~or the shaft of generator 11 of one rpm, assuming a power ; supply 17 having a voltage of 6-40 volts.
~ ' 7~
Ti~l3LE X
Xl, R2 1 mecJohm R3 l.0 kilohms R~ 1 kilohm R5 47 kilohm R6 4.7 megohms R7,R8,R9 lO0 kilohms RlO 202 kilohms 10 Cl 1 microfarad C2 22 microfarad C3 .00l microEarad C4 . 680 picofarad æl,z2 5.1 volt~
Al,A2 LM358 Dl,D4 I~ S059 To illustrate the range o-E critical speeds that can be attained merel~ b~ changing resistor R3, Table II
correlates the critical speed with various values of resistor R3.
TABLE II_ R3 ~ilohms) 10 47 100 220 470 1000 Critical speed (rpm) l 2~5 4.5 9 :Ll 25
The critical speed for generato.r ll that is utilized to determine whether control 30 maintains ;.ks switch 13A
"on" or "off" is determined by the ratio of resistors R2 - :
and R30 By chancJillg one oS- these resistors, a s~lbstan-tially dif:Eeren-t critical speecl can be e~t~bl:L~ ed. o:E cou:rse, a variable resistors coulcl be utilizecl if desi.redu On the other hand, to change -the control from a normally open swi-tch to a norma:lly c:Losed swi-tch, it is only necessary to inter change the input connec-tions ko amplifier Al. Thus~ if the connections for -terminals 32 and 36 of amplifier ~1 are reversed, control 30 will function as a normally closed switching device, with operation other~ise unchangea from that described above. By the same token, the dropout delay time during which the switch 13~ is maintained actuated after sha~t 19 of generator 11 falls below the critical speed can be readily adj.usted by changiny the resistor Rl or the capacitor Cl In order to afford a more complete and concrete example of a speed switch control constructed in accordance with the present invention and utilizing the circuit 30 of Fig. 2, specific parameters are set forth below in Table I.
With the values shown in Table I, speed switch control 30 functions as a normally open switch having a critical speed ~or the shaft of generator 11 of one rpm, assuming a power ; supply 17 having a voltage of 6-40 volts.
~ ' 7~
Ti~l3LE X
Xl, R2 1 mecJohm R3 l.0 kilohms R~ 1 kilohm R5 47 kilohm R6 4.7 megohms R7,R8,R9 lO0 kilohms RlO 202 kilohms 10 Cl 1 microfarad C2 22 microfarad C3 .00l microEarad C4 . 680 picofarad æl,z2 5.1 volt~
Al,A2 LM358 Dl,D4 I~ S059 To illustrate the range o-E critical speeds that can be attained merel~ b~ changing resistor R3, Table II
correlates the critical speed with various values of resistor R3.
TABLE II_ R3 ~ilohms) 10 47 100 220 470 1000 Critical speed (rpm) l 2~5 4.5 9 :Ll 25
3~
To a:Eford a more complete illustrati.on of the wide range of dropout ti.rne va:Lues that can be attain~d with :limited chanqes in the parame-ters of res:istor Rl and capacitor Cl, rrable III is proviAed.
TABLE III
Rl Cl Drop Out (mego~lms~ (mlcrofarads~ _ m 0.015 1.0 i.nstantaneous 0.1 1~0 0~3 0.22 1.0 1.0 0.47 1.0 1.5 1.0 1.0 2.6 2.2 1~0 . ~.5 : 4~7 1.0 7~0 10~ i.C ',`~0 ~ 1.0 lar.O
3.3 3.3 22.0 10.0 - 3.3 33.0 ~ 3 3 52.0 10.0 10.0 90.0 C~ 10.0 137.0 ~, ~
The data in Table III was determined with an external power supply 17 of twelve volts and a load current . through R~, of approximately two amperes.
~0 Speed switch control 30, constructed with the circuit values of Table I~ provides a normally open switch with a critical shaft speed of one rpm, highly suitable for use in a safety interlock control for the doors of a passenger : vehicle such as a bus. However, the same circu:;t, with only limited modifications, can be applied to an entirely dif~erent ~ applicakion~ Thus, to change control 30 to function as a : normally closed swit~h having a critical speed of 667 rpm, only the ollowing changes need be made:
Change resistor R2 to 680 kilohms.
Change resistor ~3 to 330 kilohms.
.
. ~ . . .
~dd a ;Eeeclback resistor oE 4.7 megohms Erom the output of ampliEier Al to terminal 32~
~everse the connec-tions of input t~rrninals 32 and 36 of amplifier Al.
Change resistor RlO to 22 kilohms.
Add an additional transistor, type MPS-A43, as an input stage to switching c:ircuit 13~, maintaining the Darlinyton confi~uration.
Speed switch control 30, Fig. 2, while performing well in many applications, is sensitive to changes in load conditions. That is, changes in the external circuit comprising power supply 17 and load 18 may affect the performance more ~han is desirable. This difficulty is effectively eliminated in the speed switch controL circuit 40 illustrated in Fig. 3, which provides other additional advantages as well~ ~hus, the circuit 40 of Fig. 3 provides more precise voltage regulation, allowing greater precision in control. In addition, it incorporates a single adjustable xesistor that allows for changes in the critical speed, over a broad range of approximately one rpm to 500 rpm, without change of other circuit components.
Speed switch control 40, Fig. 3, is arranged for normally-closed switching operation. The AC generator ll has one terminal connected to a resistor Rll and the other terminal connected to system ground; a voltage-regulating zener diode Zll is connected from the other terminal of resistor Pll back to ground. A series capacitor Cll and a diode D12 connect resistor Rll to the inverting input 42 of an operatlonal amplifier-Al in the threshold circui~ 12~.
An adjustable resistor R12 is connected between the common terminal of capacitor Cll and diode Dl2 ancl system gro~md/
in parallel with a diocle Dll~ Diocles D11 and D12 constitute a conventional voltagc doubler circuit. ~ capac:i.tor C12 and a resistor R13 are connec-ted in parallel from terminal 42 to system ground~
~ he non-inverting input 46 of amplifier Al is connected to a voltage divider comprisiny two resistors .~14 and R15 connected between the output line 43 of a power storage/supply circuit 22~ and system ground. ~ppropriatè
power supply connections are also made to amplifier Al from line 43 and from system groundO A feedback resistor R16 is connected from khe. output terminal 49 of amplifier Al back tO input terminal 46. The ampli~ier output ~erminal 49 is also connected ko a resistor R17 in turn connected to line 43.
The power storage/suppiy circuit 22B comprises a transistor Q11 having its emitter connected to output line 43 and having its input, line 44, connected through a blocking diode.D4 to one switch terminal 14 of a solid state switch 13B, which again constitutes a Darlington amplifier. The base o~ transistor Qll is connected to system ground through the series combination of a diode D13 and a Zener diode Z12. A resistor R18 is connected be~ween the base and collector of transistor Qll~ ~ storage capacitor C13 is connected from input 44 to system ground.
In speed switch control 4Q, the switch actuator circuit 2lB includes an operational amplifier provided with power supply connections to line 43 and to system ground~
The non-invertin~ input 45 of amplifier A2 is connected through a resistor R19 to a terminal 48 that is directly connected to the line 44. Resistor R19 is a par-t of a , 6~7~
voltage divicler wh:ich :Lnc:Ludes an additional ~esistor R21 that is returned to system ground. Terminal 45 :Ls also connectecl th.rough a diode D14 to terminal 49.
In actuator circuit 2lB, terminal 48 is fur-ther connected through a xesistor R20 to the inver-ting input 47 of amplifier ~2. Input terminal 47 is also connected to a 2ener diode Z13 that is returned to system ground.
The switching device 13B of Fig. 3 remains unchanged, in its construction and external connections~ from the device 13A shown in Fig~ 2r This includes the external connections to the power supply 17 and the load safety device 18 through the switch terminals 14 and 15, as well as the input connectîon through resistor R10.
In considering the operation of speed switch control 40, Fig. 3, it may be assumed that the control is incorporated in a safety circuit for a vehicle and that a switch SW in the load circuit is close~ as an incident to actuation of the ignition swikch for the vehicle~ at a time when the shaft 19 of generator 11 is stationary. When switch SW is closed, capacitox C13 is charged from power supply 17, through diode D4, and transistor Qll in circuit 22B begins to conduct. As the charge cn capacitor C13 builds up, the voltaye at terminal
To a:Eford a more complete illustrati.on of the wide range of dropout ti.rne va:Lues that can be attain~d with :limited chanqes in the parame-ters of res:istor Rl and capacitor Cl, rrable III is proviAed.
TABLE III
Rl Cl Drop Out (mego~lms~ (mlcrofarads~ _ m 0.015 1.0 i.nstantaneous 0.1 1~0 0~3 0.22 1.0 1.0 0.47 1.0 1.5 1.0 1.0 2.6 2.2 1~0 . ~.5 : 4~7 1.0 7~0 10~ i.C ',`~0 ~ 1.0 lar.O
3.3 3.3 22.0 10.0 - 3.3 33.0 ~ 3 3 52.0 10.0 10.0 90.0 C~ 10.0 137.0 ~, ~
The data in Table III was determined with an external power supply 17 of twelve volts and a load current . through R~, of approximately two amperes.
~0 Speed switch control 30, constructed with the circuit values of Table I~ provides a normally open switch with a critical shaft speed of one rpm, highly suitable for use in a safety interlock control for the doors of a passenger : vehicle such as a bus. However, the same circu:;t, with only limited modifications, can be applied to an entirely dif~erent ~ applicakion~ Thus, to change control 30 to function as a : normally closed swit~h having a critical speed of 667 rpm, only the ollowing changes need be made:
Change resistor R2 to 680 kilohms.
Change resistor ~3 to 330 kilohms.
.
. ~ . . .
~dd a ;Eeeclback resistor oE 4.7 megohms Erom the output of ampliEier Al to terminal 32~
~everse the connec-tions of input t~rrninals 32 and 36 of amplifier Al.
Change resistor RlO to 22 kilohms.
Add an additional transistor, type MPS-A43, as an input stage to switching c:ircuit 13~, maintaining the Darlinyton confi~uration.
Speed switch control 30, Fig. 2, while performing well in many applications, is sensitive to changes in load conditions. That is, changes in the external circuit comprising power supply 17 and load 18 may affect the performance more ~han is desirable. This difficulty is effectively eliminated in the speed switch controL circuit 40 illustrated in Fig. 3, which provides other additional advantages as well~ ~hus, the circuit 40 of Fig. 3 provides more precise voltage regulation, allowing greater precision in control. In addition, it incorporates a single adjustable xesistor that allows for changes in the critical speed, over a broad range of approximately one rpm to 500 rpm, without change of other circuit components.
Speed switch control 40, Fig. 3, is arranged for normally-closed switching operation. The AC generator ll has one terminal connected to a resistor Rll and the other terminal connected to system ground; a voltage-regulating zener diode Zll is connected from the other terminal of resistor Pll back to ground. A series capacitor Cll and a diode D12 connect resistor Rll to the inverting input 42 of an operatlonal amplifier-Al in the threshold circui~ 12~.
An adjustable resistor R12 is connected between the common terminal of capacitor Cll and diode Dl2 ancl system gro~md/
in parallel with a diocle Dll~ Diocles D11 and D12 constitute a conventional voltagc doubler circuit. ~ capac:i.tor C12 and a resistor R13 are connec-ted in parallel from terminal 42 to system ground~
~ he non-inverting input 46 of amplifier Al is connected to a voltage divider comprisiny two resistors .~14 and R15 connected between the output line 43 of a power storage/supply circuit 22~ and system ground. ~ppropriatè
power supply connections are also made to amplifier Al from line 43 and from system groundO A feedback resistor R16 is connected from khe. output terminal 49 of amplifier Al back tO input terminal 46. The ampli~ier output ~erminal 49 is also connected ko a resistor R17 in turn connected to line 43.
The power storage/suppiy circuit 22B comprises a transistor Q11 having its emitter connected to output line 43 and having its input, line 44, connected through a blocking diode.D4 to one switch terminal 14 of a solid state switch 13B, which again constitutes a Darlington amplifier. The base o~ transistor Qll is connected to system ground through the series combination of a diode D13 and a Zener diode Z12. A resistor R18 is connected be~ween the base and collector of transistor Qll~ ~ storage capacitor C13 is connected from input 44 to system ground.
In speed switch control 4Q, the switch actuator circuit 2lB includes an operational amplifier provided with power supply connections to line 43 and to system ground~
The non-invertin~ input 45 of amplifier A2 is connected through a resistor R19 to a terminal 48 that is directly connected to the line 44. Resistor R19 is a par-t of a , 6~7~
voltage divicler wh:ich :Lnc:Ludes an additional ~esistor R21 that is returned to system ground. Terminal 45 :Ls also connectecl th.rough a diode D14 to terminal 49.
In actuator circuit 2lB, terminal 48 is fur-ther connected through a xesistor R20 to the inver-ting input 47 of amplifier ~2. Input terminal 47 is also connected to a 2ener diode Z13 that is returned to system ground.
The switching device 13B of Fig. 3 remains unchanged, in its construction and external connections~ from the device 13A shown in Fig~ 2r This includes the external connections to the power supply 17 and the load safety device 18 through the switch terminals 14 and 15, as well as the input connectîon through resistor R10.
In considering the operation of speed switch control 40, Fig. 3, it may be assumed that the control is incorporated in a safety circuit for a vehicle and that a switch SW in the load circuit is close~ as an incident to actuation of the ignition swikch for the vehicle~ at a time when the shaft 19 of generator 11 is stationary. When switch SW is closed, capacitox C13 is charged from power supply 17, through diode D4, and transistor Qll in circuit 22B begins to conduct. As the charge cn capacitor C13 builds up, the voltaye at terminal
4~ in actuator circuit 21B rises. The voltage a-t terminal 45 increases proportionally, depending upon the ratio of the voltage divider Rl9,R21~ Usually, the two resistors Rl9 and R21 are app.roximately equal so that the voltage at terminal 45 is approximately one-half the voltage at terminal 48O Initially, the parallel circuit from terminal 48 to ground, through resistor R20 and æener diode Z13~ cloes not affect the voltage at terminal 45 because the zener diode ~ 21 -7~
i s non~ ondllc tiv~ .
As the voltacJe at terrllina:L 48 rises, the c~rres-poncling incxe~se in the voltage at terminal 47 ultimately xeaches the breakdown level ~or diode Z13~ Once terminal 47 reaches t~ level, the Zener diode holds terminal 47 at its breakdown voltageO Moreover, there is now a voltaye drop across resistor R20- With zener diode Z13 conducting) the voltage at terminal 48 exceeds the voltage at terminal 47 by the drop across resistor R20.
The voltage of power supply 17 is substantially higher than the breakdown v~ltage o diode Z13. Consequently, as capacitor C13 continues to charge, the voltage at terminal ~8 continues to increase, as does the voltage at terminal 45, until the voltage at terminal 45 exceeds the voltage at terminal 47~ At this point, amplifier A2, which has previously had an OFF output, at approximately ground potential, develops an o~ output which9 as applied to solid state switch 13B through resistor R10, drives the Darlington amplifier switch conductive. When this occurs, the charging circuit for capacitor C13 is effectively shunted to ground through the very low impedance afforded by the output transistor of device 13Bo The charge previously stored in capacitor C13 maintains transistor Qll conductive and also maintains amplifier A2 in the operating condition to produce an 0 actuation signal~ ~owever, the charge on capacitor C13 slowly dissipates. As it does, the potential at terrninal 45 is gradually reduced and ultimately falls back below the potential at terminal 47, which remains at the breakclown voltage for diode Z130 When the voltage at terminal 45 drops ~t~9 6L~7 4 below that at teLmirlal ~7, amp:Lifler A2 i.s cut of:E and its output: clrops to near ground potent.ial, with the result that device 13~ is switched "o:E:E". This produces a brief OFF
interval ~FigO ~) during which capaci.tor C13 recharges to a point at which the voltage at terminal A5 aga.in exceeds that at terminal 47, when the control returns to its "on"
condition, Thus, the o~ signal output of switch actuatox 21~ again corresponds to that shown in E'ig. 4, and this is the initial operating condition for the actuator circuit, making control 40 a normally closed switch control.
To establish control 40 in its "off" condition it is necessary ~o maintain the voltage a~ termir~al 4i in actuator circuit 21B below the voltage of terminal 47.
For this condition, the output from actuator circuit 21B
corresponds to the OFF signal of Fig. 4. This action is effected by threshold circuit 12~ and the connection from that circuit to actuator circuit 21B afforded by diode D14.
When control 40 is first placed in operation, with shaft 19 stationary, there is a constant .input signal to terminal 46 from the regulated source afforded by circuit 22B, line 43, and voltage divider R14,R15. There i5 no effective input at the other terminal 42 of amplifier Al. In effect, the output terminal 49 of amplifier Al remains at the power supply potential of line 43, due to the presence of the connecting resistor R17~ and any current flow from terminal A5 to terminal 49 through diode D14 is precluded.
When shaft 19 now begins to rotate, as when movement of the vehicle is started, a positive input signal is applied to terminal 42 of amplifier Al through the rectifier circuit comprising voltage doublex Dll,D12, the applied voltaye increasing with increasing speed. when the voltacJe at termillal ~2 reaches the same level as the voltage at kerminal ~6, the output terminal 49 oE amplifier Al goes to approximately yround potential. This allows a cuxrent flow from terminal 45 throuyh diode D14 to terminal 49, so that terminal 45 is also driven to near ground potential.
This maintains amplifier ~2 in an operating condition in which its output is essentially at ground t the OFF signal of Fig. 4, actuating swltch 13B to its "off" condition.
Initially, the voltaye at terminal 46 in threshold circuit 12B is fixed, since the voltage on line 43 is well regulated by the power storaye/supply circuit 22~. However, as the voltage at the amplifier output terminal 49 rises, the feedback resistor R16 causes some increase in the potential at terminal 46. This provides a limited hysteresis ef~ect in the operation of threshold circuit 12B.
As in the previously described embodiment~
threshold circuit 12B af~ords a dropout delay time~ in this instance determined by the parameters selected for capacitors C12 and resistor R13 The use of the voltage coupler circuit Dll,D12 increases the sensitivity of the threshold circuit.
~he adjustable resistor R12 affords an effective control for the critical speed of control 40. This one adjustable circuit element makes it possible to adjust the control for operation at critical speeds from 500 rpm down to two rpm or even ; lowar with no change of other circuit components~
Furthermore, as noted above, the control 40 of Fig. 3 is not particularlv load-sensitlve. A decrease in the load resistance RL, or other load change causing an increased load current, simply decreases the duration T2 of ~,f~
of the brieE OE~F inte.rvals in the ON signal output -Erom actuator circuit 21~ ~see ~ If the clrcult is properl~ constructe~t with adequate charging time for capacikor C13 for relatively h:igh load currents, it will function over a broad range of load current changes with no difficulty.
There may also be some variation in the overall period Tl or the recurring OFF interval pulses in the ON siynal output from actuator circuit 2lB, but it is a simple matter to keep the frequency of these OFF pulses hiyh enough so that they do not affect the operation of the load safety device 18~
~t will be recogni~ed that control 40 can be changed from a normally closed switching device,.as illustrated~ to a normally open device, again merely by reversing the circuit connections to the input terminals 42 and 46 of amplifier Al.
Typical circuit parameters for control 40, Fig~ 3, for operation with a power supply of six to 40 volts DC
a~d a maximum load current of five amperes, and with a critical speed range of approximately 2-500 rpm, are set forth in Table IV~ It will b~. understood that the specific circuit parameters incorporated in the tables are presented solely by way of illustration and in no sense as a limitation on the inventionO
- ~5 -~ 7~
rJ['ABl~E_V
R10 270 ~ ohms Rll lOK ~- ohms Rl2 ~adjustable) 1 m~gohm Rl3 2.20 Kilohms Rl~ 15 ~Cilohms ~15 18 Kilohms Rl6 22 Kilohms R17 10 Kilohms 10 Rl8 . 1.2 Kilohms Rl9 12 ICilohms R20 . 1 Ki 10~Q
R21 . 1.0 Kilohms Cll ~l microfarad - ~
Cl2 . l ml~rofarad Cl3 6~8 microfarad Z~l 5.1 volts , . .
20 Z12 6~2 volts Z13 3.6 volts D4 Diode l ampere Dll Diode 1 ampere ` D12 Diode 1 ampere D13 Diode 1 ampere D14 Diode 1 ~mpere Al,A2 ~M358 ;
i s non~ ondllc tiv~ .
As the voltacJe at terrllina:L 48 rises, the c~rres-poncling incxe~se in the voltage at terminal 47 ultimately xeaches the breakdown level ~or diode Z13~ Once terminal 47 reaches t~ level, the Zener diode holds terminal 47 at its breakdown voltageO Moreover, there is now a voltaye drop across resistor R20- With zener diode Z13 conducting) the voltage at terminal 48 exceeds the voltage at terminal 47 by the drop across resistor R20.
The voltage of power supply 17 is substantially higher than the breakdown v~ltage o diode Z13. Consequently, as capacitor C13 continues to charge, the voltage at terminal ~8 continues to increase, as does the voltage at terminal 45, until the voltage at terminal 45 exceeds the voltage at terminal 47~ At this point, amplifier A2, which has previously had an OFF output, at approximately ground potential, develops an o~ output which9 as applied to solid state switch 13B through resistor R10, drives the Darlington amplifier switch conductive. When this occurs, the charging circuit for capacitor C13 is effectively shunted to ground through the very low impedance afforded by the output transistor of device 13Bo The charge previously stored in capacitor C13 maintains transistor Qll conductive and also maintains amplifier A2 in the operating condition to produce an 0 actuation signal~ ~owever, the charge on capacitor C13 slowly dissipates. As it does, the potential at terrninal 45 is gradually reduced and ultimately falls back below the potential at terminal 47, which remains at the breakclown voltage for diode Z130 When the voltage at terminal 45 drops ~t~9 6L~7 4 below that at teLmirlal ~7, amp:Lifler A2 i.s cut of:E and its output: clrops to near ground potent.ial, with the result that device 13~ is switched "o:E:E". This produces a brief OFF
interval ~FigO ~) during which capaci.tor C13 recharges to a point at which the voltage at terminal A5 aga.in exceeds that at terminal 47, when the control returns to its "on"
condition, Thus, the o~ signal output of switch actuatox 21~ again corresponds to that shown in E'ig. 4, and this is the initial operating condition for the actuator circuit, making control 40 a normally closed switch control.
To establish control 40 in its "off" condition it is necessary ~o maintain the voltage a~ termir~al 4i in actuator circuit 21B below the voltage of terminal 47.
For this condition, the output from actuator circuit 21B
corresponds to the OFF signal of Fig. 4. This action is effected by threshold circuit 12~ and the connection from that circuit to actuator circuit 21B afforded by diode D14.
When control 40 is first placed in operation, with shaft 19 stationary, there is a constant .input signal to terminal 46 from the regulated source afforded by circuit 22B, line 43, and voltage divider R14,R15. There i5 no effective input at the other terminal 42 of amplifier Al. In effect, the output terminal 49 of amplifier Al remains at the power supply potential of line 43, due to the presence of the connecting resistor R17~ and any current flow from terminal A5 to terminal 49 through diode D14 is precluded.
When shaft 19 now begins to rotate, as when movement of the vehicle is started, a positive input signal is applied to terminal 42 of amplifier Al through the rectifier circuit comprising voltage doublex Dll,D12, the applied voltaye increasing with increasing speed. when the voltacJe at termillal ~2 reaches the same level as the voltage at kerminal ~6, the output terminal 49 oE amplifier Al goes to approximately yround potential. This allows a cuxrent flow from terminal 45 throuyh diode D14 to terminal 49, so that terminal 45 is also driven to near ground potential.
This maintains amplifier ~2 in an operating condition in which its output is essentially at ground t the OFF signal of Fig. 4, actuating swltch 13B to its "off" condition.
Initially, the voltaye at terminal 46 in threshold circuit 12B is fixed, since the voltage on line 43 is well regulated by the power storaye/supply circuit 22~. However, as the voltage at the amplifier output terminal 49 rises, the feedback resistor R16 causes some increase in the potential at terminal 46. This provides a limited hysteresis ef~ect in the operation of threshold circuit 12B.
As in the previously described embodiment~
threshold circuit 12B af~ords a dropout delay time~ in this instance determined by the parameters selected for capacitors C12 and resistor R13 The use of the voltage coupler circuit Dll,D12 increases the sensitivity of the threshold circuit.
~he adjustable resistor R12 affords an effective control for the critical speed of control 40. This one adjustable circuit element makes it possible to adjust the control for operation at critical speeds from 500 rpm down to two rpm or even ; lowar with no change of other circuit components~
Furthermore, as noted above, the control 40 of Fig. 3 is not particularlv load-sensitlve. A decrease in the load resistance RL, or other load change causing an increased load current, simply decreases the duration T2 of ~,f~
of the brieE OE~F inte.rvals in the ON signal output -Erom actuator circuit 21~ ~see ~ If the clrcult is properl~ constructe~t with adequate charging time for capacikor C13 for relatively h:igh load currents, it will function over a broad range of load current changes with no difficulty.
There may also be some variation in the overall period Tl or the recurring OFF interval pulses in the ON siynal output from actuator circuit 2lB, but it is a simple matter to keep the frequency of these OFF pulses hiyh enough so that they do not affect the operation of the load safety device 18~
~t will be recogni~ed that control 40 can be changed from a normally closed switching device,.as illustrated~ to a normally open device, again merely by reversing the circuit connections to the input terminals 42 and 46 of amplifier Al.
Typical circuit parameters for control 40, Fig~ 3, for operation with a power supply of six to 40 volts DC
a~d a maximum load current of five amperes, and with a critical speed range of approximately 2-500 rpm, are set forth in Table IV~ It will b~. understood that the specific circuit parameters incorporated in the tables are presented solely by way of illustration and in no sense as a limitation on the inventionO
- ~5 -~ 7~
rJ['ABl~E_V
R10 270 ~ ohms Rll lOK ~- ohms Rl2 ~adjustable) 1 m~gohm Rl3 2.20 Kilohms Rl~ 15 ~Cilohms ~15 18 Kilohms Rl6 22 Kilohms R17 10 Kilohms 10 Rl8 . 1.2 Kilohms Rl9 12 ICilohms R20 . 1 Ki 10~Q
R21 . 1.0 Kilohms Cll ~l microfarad - ~
Cl2 . l ml~rofarad Cl3 6~8 microfarad Z~l 5.1 volts , . .
20 Z12 6~2 volts Z13 3.6 volts D4 Diode l ampere Dll Diode 1 ampere ` D12 Diode 1 ampere D13 Diode 1 ampere D14 Diode 1 ~mpere Al,A2 ~M358 ;
Claims (8)
1. A two-terminal precision speed switch control actuated by changes in the rotational speed of a shaft and adaptable to operation over a broad speed range down to less than ten rpm comprising:
a sub-fractional AC generator, connectible to a rotary shaft, for generating an AC signal having an amplitude which varies with changes in shaft speed;
a threshold circuit, connected to the generator, for developing first and second threshold signals, one indicative of an AC signal input exceeding a given threshold amplitude corresponding to a critical shaft speed and the other indicative of an AC signal input below the threshold amplitude;
a switch actuator circuit, coupled to the threshold circuit for developing ON and OFF switch actuation signals corresponding to the first and second threshold signals, the OFF signal being a continuous DC signal and the ON signal being a semi-continuous DC signal of high duty cycle including brief recurring OFF intervals;
a solid-state switching circuit, having two switch terminals connectible in series with an external power supply in an operating circuit for a controlled load and having an actuation input connected to the switch actuator circuit, actuatable to an "on" condition in which the impedance across the switch terminals is very low, in response to the ON
switch actuation signal, and actuatable to an "off" condition in which the impedance across the switch terminals is very high, in response to the OFF switch actuation signal;
and a power storage/supply circuit, connected in parallel with the switch terminals, affording a power supply for the threshold circuit and the switch actuator circuit, and including a storage device which is re-charged during intervals in which the switching circuit is in its "off" condition.
a sub-fractional AC generator, connectible to a rotary shaft, for generating an AC signal having an amplitude which varies with changes in shaft speed;
a threshold circuit, connected to the generator, for developing first and second threshold signals, one indicative of an AC signal input exceeding a given threshold amplitude corresponding to a critical shaft speed and the other indicative of an AC signal input below the threshold amplitude;
a switch actuator circuit, coupled to the threshold circuit for developing ON and OFF switch actuation signals corresponding to the first and second threshold signals, the OFF signal being a continuous DC signal and the ON signal being a semi-continuous DC signal of high duty cycle including brief recurring OFF intervals;
a solid-state switching circuit, having two switch terminals connectible in series with an external power supply in an operating circuit for a controlled load and having an actuation input connected to the switch actuator circuit, actuatable to an "on" condition in which the impedance across the switch terminals is very low, in response to the ON
switch actuation signal, and actuatable to an "off" condition in which the impedance across the switch terminals is very high, in response to the OFF switch actuation signal;
and a power storage/supply circuit, connected in parallel with the switch terminals, affording a power supply for the threshold circuit and the switch actuator circuit, and including a storage device which is re-charged during intervals in which the switching circuit is in its "off" condition.
2. A speed switch control according to Claim 1 in which the switch actuator circuit is a monostable trigger circuit having a duty cycle of the order of 95% or more.
3. A speed switch control according to Claim 1 in which the switch actuator circuit comprises an amplifier responsive to the level of charge on a storage device comprising a part of the power storage/supply circuit.
4. A speed switch control according to Claim 3 in which the switch actuator circuit comprises an operational amplifier having an inverting input and a non-inverting input, one input of the amplifier being connected to a voltage divider affording an input voltage proportional to the charge on the storage device in the power storage/supply circuit, the other input of the amplifier being connected to a clamp circuit affording an input voltage limited to a predetermined maximum value.
5. A speed switch control according to Claim 4, in which the threshold circuit comprises an amplifier having its output connected to theone input of the actuator circuit amplifier in a circuit that maintains that one actuator circuit amplifier input at a reference level whenever one of the threshold signals is present.
6. A speed switch control according to Claim 1 in which the power storage/supply circuit includes a voltage-regulated output, and in which the threshold circuit comprises an operational amplifier having an inverting input and a non-inverting input, with one amplifier input coupled to the generator through a rectifier circuit and the other amplifier input connected to the regulated output of the power storage/
supply by a reference circuit, in which a change between normally-closed and normally-open operation for the switching circuit is effected by interchanging the input connections to that operational amplifier.
supply by a reference circuit, in which a change between normally-closed and normally-open operation for the switching circuit is effected by interchanging the input connections to that operational amplifier.
7. A speed switch control according to Claim 6 in which the rectifier circuit in the threshold circuit includes a time delay circuit to delay a change in operating condition of the switching circuit upon deceleration of the generator to a speed below the critical speed.
8. A speed switch control according to Claim 6 in which the rectifier circuit in the threshold circuit includes an adjustable impedance for varying the critical speed of the control over a broad speed range.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US839,193 | 1977-10-04 | ||
| US05/839,193 US4168516A (en) | 1976-11-26 | 1977-10-04 | Precision speed switch control |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1096474A true CA1096474A (en) | 1981-02-24 |
Family
ID=25279098
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA312,101A Expired CA1096474A (en) | 1977-10-04 | 1978-09-26 | Precision speed switch control |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA1096474A (en) |
| DE (1) | DE2843278C2 (en) |
| FR (1) | FR2405595A1 (en) |
| GB (1) | GB2006999B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2542468B1 (en) * | 1983-03-10 | 1985-11-22 | G G Electricite | AMPLIFIER FOR POSITION SENSOR |
| ATE249266T1 (en) * | 2000-02-18 | 2003-09-15 | Heartsine Technologies Ltd | DEFIBRILLATOR |
| JP4630282B2 (en) | 2003-05-15 | 2011-02-09 | タッチセンサー テクノロジーズ，エルエルシー | 2-wire touch sensor interface |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3207950A (en) * | 1962-10-15 | 1965-09-21 | Eaton Mfg Co | Control for electrical coupling apparatus |
| US3440433A (en) * | 1966-05-19 | 1969-04-22 | Bendix Corp | Aircraft starter control |
| US3826985A (en) * | 1971-06-04 | 1974-07-30 | Motorola Inc | Self-powered tachometer circuit |
| DE2135912A1 (en) * | 1971-07-17 | 1973-03-22 | Lestra Ag | DEVICE FOR SCANNING SPEED VALUES IN MOTOR VEHICLES |
| US3845375A (en) * | 1973-11-09 | 1974-10-29 | Mclaughlin Ward & Co | Electronic rotational sensor |
-
1978
- 1978-09-26 CA CA312,101A patent/CA1096474A/en not_active Expired
- 1978-10-04 GB GB7839326A patent/GB2006999B/en not_active Expired
- 1978-10-04 FR FR7828408A patent/FR2405595A1/en active Granted
- 1978-10-04 DE DE19782843278 patent/DE2843278C2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2843278C2 (en) | 1983-01-13 |
| FR2405595A1 (en) | 1979-05-04 |
| GB2006999A (en) | 1979-05-10 |
| FR2405595B1 (en) | 1984-02-03 |
| GB2006999B (en) | 1982-11-24 |
| DE2843278A1 (en) | 1979-04-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |