US2892105A

US2892105A - Free-running relay multivibrator

Info

Publication number: US2892105A
Authority: US
Inventors: Jr John Howard Speer
Original assignee: Hughes Aircraft Co
Current assignee: Raytheon Co
Priority date: 1956-04-10
Filing date: 1956-04-10
Publication date: 1959-06-23
Anticipated expiration: 1976-06-23

Description

June 23, 1959 .1. H. SPEER, JR

FREE-RUNNING RELAY MULTIVIBRATOR Filed April 10, 1956 GND.

OPEN

Jon/v l1. .SPEER JR.

INVEN TOR ATTORNEY United States Patent Ofiice 2,892,105 FREE-RUNNING RELAY MULTIVIBRATOR John Howard Speer, Jr., Santa Monica, Calif., assignor to Hughes Aircraft Company, Culver City, Calif., a corporation of Delaware Application April 10, 1956, Serial No. 577,400 Claims. (Cl. 307-132) The present invention relates to multivibrators in general and more specifically to a free-running relay multivibrator that produces pulse-type oscillations controllable as to frequency, phase, and as to the on-oft times of the pulses.

Standard free-running vacuum tube multivibrators and relay oscillators are customarily used to provide pulsetype oscillations. at two sets of output terminals. In the case of vacuum tube multivibrators, the frequency as Well as the on-01f times of the pulses may be varied. In the case of relay oscillators, on the other hand, the frequency of the pulses can be varied. In neither case can the phase between the oscillations be adjusted. More specifically, in the prior art multivibrator and oscillator devices, the phase is fixed, the pulses produced at one set of output terminals being 180 out of phase with the pulses produced at the other set of output terminals. Phase adjustment may be important where the pulses are employed to drive incremental devices, such as solenoid driven switches and incremental motors.

It is, therefore, an object of the present invention to provide a free-running relay multivibrator that produces pulse type oscillations controllable as to phase as well as to the frequency and on-ofi times of the pulses.

The present invention overcomes the phase limitations of the prior art multivibrator and relay oscillator devices by providing a relay multivibrator whose output pulse-type oscillations may be controlled as to phase by adjustment of the circuit parameters. More particularly, a pair of relays are interconnected by impedance means having exponential voltage rise and decay characteristics. Upon applying a direct-current voltage to the relay multivibrator, a voltage alternately rising and decaying exponentially is developed across the solenoid of each relay. By varying the appropriate parameters of the impedance means, that is, by varying either the rise or decay characteristics of the impedance means, or both, the phase or" the oscillations as well as the frequency and on-oii times of the pulses may be varied as desired.

The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description considered in connection with the accompanying drawings in which an embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only, and are not intended as a definition of the limits of the invention.

Fig. l is a schematic circuit of a free-running relay multivibrator according to the present invention;

Fig. 2 is a composite diagram of waveforms repre sentative of the voltages. produced at various points in the circuit of Fig. l and Fig. 3 is a composite diagram of waveforms illustrating the closing and opening of the relay contacts of the relays shown in Fig. 1.

Referring now to the drawings, there is shown in Fig. 1

2,892,105 Patented June 23, 1959 a preferred embodiment of a free-running relay multivibrator, according to the present invention, that pro duces pulse-type oscillations at a first pair of output terminals 10 and at a second pair of output terminals 11, the relative phase of the oscillations as well as the frequency and on-off time of the pulses being adjustable by adjustment of the circuit parameters.

As shown in the figure, the relay multivibrator basically comprises a pair of relays, generally designated 12 and 13 shown here as being of electromagnetic type. More specifically, relay 12 includes a core 14 having a coil 15 wound thereon, a pair of relay contacts 16 and 17, and a relay arm 18 positioned between relay contacts 16 and 17. The relay arm is shown as being in physical and electrical contact with relay contact 16 in one relay position and magnetically coupled to core 14 as indicated by dashed line 20. In the other relay position, the relay arm 18 will, of course, be in electrical contact with the second relay contact 17. Similarly, relay 13 includes a core 21 having a coil 22 wound thereon, a pair of

relay contacts

23 and 24, and a relay arm 25 positioned between

relay contact

23 and 24. The relay arm is shown as being physically and electrically in contact with relay contact 23 in a first position and magnetically coupled to core 21 as indicated by dashed line 26. In the second position, the relay arm 25 will be in electrical contact with relay contact 24. Obviously, other types of relay construction may also be utilized.

The relay multivibrator further includes a pair of capacitors 2'7 and 28, capacitor 27 being electrically connected in parallel with coil 15 and capacitor 28 being electrically connected in parallel with coil 22. A variable resistor 30 is preferably connected in parallel with capacitor 27 and a variable resistor 31 is preferably connected in parallel with capacitor 28. Thus, coil 15, capacitor 27 and variable resistor 30' form a parallel combination, one junction of the combination being connected to ground and the other junction of the combination, designated 32, being electrically connected through a variable resistor 33 to relay contact 24. Similarly, coil 22, capacitor 28 and variable resistor 31 form a parallel combination, one junction of the combination being connected to ground and the other junction of the combination, designated 34, being electrically connected through a variable resistor 35 to relay contact 16.

One terminal of terminals 10 is connected to ground, the other of said terminals being electrically connected to relay contact 17. Similarly, one terminal of terminals 11 is grounded, the other of said terminals being electrically connected to relay contact 23. Relay arm 18 is electrically connected to relay arm 25 by means of lead 36 which is electrically connected to a source of direct-current voltage indicated as B+.

Considering now the operation, direct-current voltage from the voltage source B+ is applied to the relay multivibrator at a time t as shown in Fig. 2. Accordingly, at time t electrical current commences to flow from the voltage source B+ through relay arm 18, relay contact 16, variable resistor 35 and the parallel combination of coil 22, capacitor 28 and resistor 31 to ground. As a result, capacitor 28 positively charges at an exponential rate and, in consequence thereof, the potential at'junction point 34 or, stated differently, the voltage across capacitor 28 increases exponentially toward a voltage level V as shown by waveform 36 in Fig. 2, V being equal to B+ voltage multiplied by where R6011 being the resistance of coil 22, and R l-R being the resistance of

resistors

31 and 35, respectively. The voltage across capacitor 28, that is, voltage 36 reaches the pull-in value of voltage of relay 13 at time Consequently, at time t relay arm 25 is magnetically attracted by core 21 so that the arm moves quickly out of electrical contact with relay contact 23 and into electrical contact with relay contact 24, as indicated by waveform 37 of Fig. 3.

It should be noted that from time t to time 1 zero voltage is produced at output terminals 10, as shown by waveform 38 of Fig. 2, whereas B+ voltage is produced at output terminals 11, as shown by waveform 40 of Fig. 2. This will be obvious from the fact that during time interval t 1,, terminals are electrically disconnected from the B+ voltage source while, during the same time interval, terminals 11 are electrically connected to the voltage source.

Upon pull-in of relay 13 at time 1 the circuit of relay 12 is electrically connected through resistor 33 to voltage source B+. As a result, the potential at junction point 32 or, stated difierently, the voltage across capacitor 27 commences to rise exponentially toward a voltage level V; for the reasons previously explained in connection with capacitor 28. The exponential rise of voltage across capacitor 27 is shown as wave form 41 in Fig. 2.

The voltage developed across capacitor 27, that is, voltage 41 reaches the pull-in value of voltage of relay 12 at time t Consequently, at time relay arm 18 is magnetically attracted by core 14 so that the arm moves quickly out of electrical contact with relay contact 16 and into electrical contact with relay contact 17, as indicated by waveform 42 in Fig. 3. Thus, at time 1 output tor-- minals '10 are electrically connected to the voltage source and voltage 38 produced at these output terminals immediately rises to a 13+ voltage level.

Upon pull-in of relay 12, the circuit of relay 13 is electrically disconnected from the 13+ voltage source. As a result, capacitor 28 discharges exponentially through coil 22 and resistor 31 so that voltage 36 developed across capacitor 28 decreases exponentially toward zero voltage. Voltage 36 reaches the drop-out value of voltage of relay 13 at time t At this point in time, relay arm is released by core 21 and, as a result, the arm quickly moves out of electrical contact with relay contact 24 and into electrical contact with relay contact 23, as shown by waveform 37 of Fig. 3. Thus, at time t output terminals 11 are again electrically connected to voltage source B+ and voltage 40 produced at these output terminals is again at a 13+ voltage level.

Furthermore, the drop-out of relay 13 electrically disconnects or breaks the circuit between relay 12 and voltage source B+ so that capacitor 27 commences to discharge exponentially through coil 15 and resistor 30.

Accordingly, voltage 41 developed across capacitor 27 commences to decrease exponentially toward zero voltage. Voltage 41 reaches the dropout value of voltage of relay 12 at time 12,, and, when this occurs, relay arm 18 quickly moves out of electrical contact with relay contact 17 and into electrical contact with relay contact 16, as shown by waveform 42 of Fig. 3. Consequently, at time 1 output terminals 10 are again electrically disconnected from the voltage source and voltage 38 produced at output terminals 10 immediately drops from B+ to zero. At the same time, the electrical circuit of relay 13 is again connected to voltage source 13+ and voltage 36 developed across capacitor 28 again increases exponentially toward voltage V Thus,

relays

12 and 13 are alternately connected and disconnected to and from voltagesource 8+ and, in consequence thereof,

voltages

38 and 40 produced at output terminals 10 and 11, respectively, are that of a pulse-type oscillation, as illustrated by

waveforms

38 and 40 of Fig. 2.

It should be noted that the pull-in and drop-out rates of both relays are determined by the circuit parameters,

Cit

namely,

variable resistors

30, 31, 33 and 35 and

capacitors

27 and 28, and, therefore, that the relative phase of the oscillations produced at output terminals 10 and 11, as well as the frequency and on-oft times of the pulses, are fixed for any one set of values of these parameters. However, the frequency phase and on-off time may be fixed at any other desired values by suitable adjustment of the circuit parameters. In this regard, it will be obvious to those skilled in the art that adjustment of

resistors

30 and 31 will have a greater effect on frequency and on-oil time than

resistors

33 and 35 and, conversely, adjustment of

resistors

33 and 35 will have a greater efiect on relative phase than

resistors

30 and 31.

It should further be noted that the relay multivibrator of the present invention may be modified in various ways without departing from the spirit and scope of the invention. Thus, for example, to produce the same operation and results previously described, variable inductors may be substituted for

variable resistors

33 and 35,

capacitors

27 and 28 taken out of the circuit, and inductors inserted in the circuit in series with each of the relay coils 15 and 22. More explicitly, a first inductor may be connected in series between junction point 32 and the upper end of coil 15, and a second inductor may be connected in series between junction point 34 and the upper end of coil 22.

What is claimed as new is:

l. A free-running relay multivibrator that produces pulse-type oscillations in response to an electrical connection thereto of a direct-current source of voltage, said multivibrator comprising: first and second electromagnetic relays, each relay having first and second relay contacts and a relay arm electrically connected to the direct current voltage source and normally in electrical contact with the first relay contact; and first and second impedance means each electrically interconnecting the coil of one relay to a contact of the other relay, each impedance means having variable exponential voltage rise and decay characteristics, said first impedance means being electrically connected across the coil of said first relay and to the second relay contact of said second relay and said second impedance means being electrically connected across the coil of said second relay and to the first relay contact of said first relay, whereby a voltage alternately rising and decaying exponentially is developed across the coil of each relay.

2. The relay multivibrator defined in claim 1 wherein said first and second impedance means include first and second capacitors electrically connected across the coils of said first and second relays, respectively, said first and second impedance means further including first and second resistors, respectively, said first resistor being electrically connected between said first capacitor and the second relay contact of said second relay and said second resistor being electrically connected between said second capacitor and the first relay contact of said first relay.

3. A free-running relay multivibrator for producing pulse-type oscillations at first and second pairs of output terminals in response to the connection thereto of a direct-current source of voltage, the frequency and relative phase of the oscillations being adjustable, said multivibrator comprising: first and second electromagnetic relays, each relay including first and second relay contacts and a relay arm normally individually connected to the first relay contacts when said relays are not energized, the second and first relay contacts of said first and second relays being electrically connected to the first and second pairs of output terminals, respectively, each relay arm. being electrically connected to the source of direct-current voltage; first and second capacitors electrically connected in parallel with the coils of said first and second relays, respectively; first and second variable resistors electrically connected in parallel with said first and second capacitors, respectively; and third and fourth variable resistors, said third resistor being electrically connected between said first capacitor and the second relay contact of said second relay and said fourth resistor being electrically connected between said second capacitor and the first relay contact of said first relay.

4. A free-running relay multivibrator that produces pulse-type oscillations in response to the electrical connection thereto of a direct-current source of voltage, said multivibrator comprising: first and second e1ectromagnetic relays, each relay having first and second relay contacts and a relay arm electrically connected to the directcurrent voltage source and normally in electrical contact with the second relay contact; first and second variable impedance elements, said first impedance element being electrically connected between the coil of said first relay and the first relay contact of said second relay and said second impedance element being electrically connected between the coil of said second relay and the second relay contact of said first relay; and first and second variable impedance means electrically connected across the coils of said first and second relays, respectively, said first and second impedance means coacting with said first and second impedance elements, respectively, to produce a voltage across the coil of each relay that alternately rises and decays exponentially.

5. In a relay multivibrator circuit, a power source; first and second relays, each having a movable contact arm connected to said power source, and first and second contacts arranged to be alternatively engaged by said contact arm; first and second load terminals arranged to be connected by said relays alternately to said power source; and means for controlling the waveform and phase relations of current delivered to said load terminals, comprising first and second controlled impedances, shunted across each of said relays, and a variable impedance connected between each of said first and second controllable irnpedances and the one of the relay contacts associated with the other of said relays.

References Cited in the fileof this patent UNITED STATES PATENTS Hines Mar. 12, 1946 FOREIGN PATENTS 528,132 Great Britain Oct. 27, 1940