US3527993A - Solid state motor driven antenna rotator control circuit - Google Patents

Description

P 1970 s. TIC'KNOR 3,527,993

SOLID STATE MOTOR DRIVEN ANTENNA ROTATOR CONTROL CIRCUIT Filed Feb. 12, 1968 INVENTOR. SERGE] L. TICK/VCR BYWZW United States Patent Oflice 3,527,993 Patented Sept. 8, 1970 3,527,993 SOLID STATE MOTOR DRIVEN ANTENNA ROTATOR CONTROL CIRCUIT Sergei L. Ticknor, Earlville, N.Y., assignor, by mesne assignments, to Jerrold Electronics Corporation, Philadelphia, Pa., a corporation of Delaware Filed Feb. 12, 1968, Ser. No. 704,633 Int. Cl. G05b 11/12 U.S. Cl. 318-674 2 Claims ABSTRACT OF THE DISCLOSURE An antenna rotational control system is provided having a console control comprising a variable potentiometer which is an arm of a bridge, the other arm being coupled to the antenna. A solid state control circuit including a DC motor and a stabilized dual SCR circuit drives said antenna in response to position control positions on said console.

My invention relates to an antenna rotator control circuit. More particularly, it relates to a television antenna positioned on a roof top, the direction of which may be operated by manual controls from a command console inside the house.

The antenna rotator system must operate effectively over long periods of time during the winter and surnmer. It is necessarily subjected to wide temperature variations as well as other environmental problems caused by wind, snow, rain and storms. It is desirable, therefore, to have an antenna rotator system which is simple and most reliable, and which will stand up over a long period of time.

Prior antenna rotator systems have utilized a motor which responds to the imbalances in a bridge circuit. These systems have included relays in control circuits to actuate and drive an AC motor in the respective desired directions. One of the common problems in such systems is that the relays themselves carry substantial currents and over a long period of time arcing, wear and other mechanical problems have appeared.

An object of my invention is to provide an improved and reliable antenna rotator motor control system.

A further object of my invention is to provide a' simple antenna rotator control system utilizing a DC motor.

Still another object of my invention is to provide an antenna rotator system which does not require relays and eliminates the problem of arcing and reduces the requirements of servicing.

Another object of my invention is to provide a console operated antenna rotator system which inherently cannot lose synchronization.

Briefly, in my invention 1 provide an antenna otator system including a DC motor which responds to imbalances in a bridge circuit. When a person wishes to have the direction of the antenna changed, he provides a manual operation or command which alters the resistance ratio in one leg of the bridge and thereby provides a voltage differential. This differential is picked up by the motor control system to drive the DC motor which in'turn rotates the antenna. When the antenna rotates, the resistance ratio in the other leg of the bridge is varied in a direction towards bridge equalization. When the antenna is pointed in the right direction, the bridge is balanced. In the preferred embodiment, the motor control comprises common cathode dual SCR circuits, the triggering of which is caused by the bridge dilferential and provides the positive or negative half cycles from the AC power supply to the DC motor to cause motor drive in either direction.

One of the advantages achieved with the elimination of relays is that the console operation is completely silent. The system is more reliable because there are no moving parts except for the potentiometers in the bridge circuits.

The DC motor operation requires lower amounts of power and results in essentially cooler operation. Because of the speed torque characteristic of the DC motor, the response is quicker and higher rotational speeds are achieved.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best uderstood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawing, wherein:

FIG. 1 is a circuit diagram illustrating my antenna rotator motor control.

Referring now to FIG. 1, there is shown a motor M1 connected to a drive shown diagrammatically at 10. One side of M1 isgrounded. The drive 10 is coupled to the antenna shown at 20 to cause it to move in accordance therewith. In the embodiment shown, the drive 10 causes a ring to rotate. The ring houses or contains the potentiometer resistance element R2. The drive 10, when driven counterclockwise, causes clockwise rotation of R2 The antenna position detector comprises bridge potentiometers R1 and R2 having respective wipers W1 and W2. If the position of the wipers on the potentiometer is the same with respect to each other, i.e., the resistance ratio formed thereby is the same, there will be 0 volt between points 1 and 2. If there is a difference in mechanical positioning between W1 and W2, it will be indicated by a voltage proportional to this offset with a polarity indicating the offset direction.

R1 is located in a unit, such as a console, inside the house. Wiper W1 of potentiometer R1 may be manually operated to position the antenna in any desired direction.

A transformer T1 having a dual secondary S1 and S2 supplies power for the operation of the SCR motor control circuit and the bridge circuit.

S1 is connected to a full wave bridge rectifier 30 having rectifiers CR5, CR6, CR7, CR8. This supplies DC for the bridge control potentiometers R1 and R2 at terminals 11, 12 and 21, 22.

The operation of the motor M1 is controlled by the voltages obtained from the secondary S2. The AC voltage at S2 consists of a sine wave having positive and negative halves. In the operation of this system, either the positive halves of the signal or the negative halves of the voltage signals are applied to the motor. When the positive half cycles are applied, the motor is caused to rotate in one direction and when the negative halves are applied, the voltage causes the motor to rotate in the opposite direction.

The control circuit comprises an input resistor R3 coupled from wiper W2 of potentiometer R2 and an input resistor R4 coupled from wiper W1 of potentiometer R1. A dual control rectifier circuit is employed having SCR1 and SCR2, the cathodes being connected together. The gate electrode of SCR2 is coupled to R4 and the anode of SCR2 is connected to the right side r of the secondary S2. The gate electrode of SCR1 is coupled to R3 while the anode of SCR1 is connected to the grounded side of the motor over 118. The other side of the motor is connected through a radio frequency choke or inductor RFCl, and by conductor to the left side I of the secondary S2.

Series capacitors C2 and C3 are connected across from one gate electrode to the other. Rectifier CR1 is connected between the gate and anode of SCR1, and CR2,

biased in the same direction as CR1, is connected from.

of SCR2. CR4, biased in the same direction as CR3, is connected from the gate of SCR2 to the collector'of SCR2. Thus, if SCR2 is on, CR1 and CR2 are conducting and SCRl is off; if SCRI is on, CR3 and CR4 are conducting and SCR2 is off.

When there is a voltage present at Rla and R2a, as a result of a console command rotation of R1, it will be applied across the two SCR gate resistors R3 and R4. SCRl or SCR2 must have a positive gate to cathode voltage (approximately .6 volt) to trigger the gate and cause conduction from cathode to anode.

When the wiper is moved easterly, as shown by the dotted lines, SCR2 conducts during the half cycle when terminal r of the secondary of T1 is positive, as indicated. The circuit is completed from the right side r, through SCR2, conductors 120, 116, 115 through CR2 and CR1, and conductor 118 to the common side of the motor. When CR2 conducts and CR3 blocks, all the bridge output voltage appears across the gate and cathode of SCR2. If this is above the minimum gate trigger voltage (.6 volt), SCR2 will conduct, allowing a positive path through SCR2, CR2 and CR1. Turning the antenna from T1 across the motor M1 causing it to run, turning the antenna. At this time, terminal 1 of S2 is negative and the negative half cycle is applied over conductor 110 RFCl to the motor. This allows a half wave rectified voltage from T1 across the motor M1 causing it to run, turning the antenna. The motor drives the antenna and the potentiometer ring of the bridge 2 in a manner to compensate for the imbalance and in an easterly direction. When the antenna turns the potentiometen'wiper W2 also moves towards its identical position with 1. When the differential voltages lowers to the trigger voltage (.6 volt) again, the SCR will drop out of conduction stopping antenna rotation by the motor drive system.

A positive voltage appears across R3 when the wiper of potentiometer R1 is moved westerly, as indicated by the dotted lines. SCRl then is turned on during the half cycle when terminal r is negative causing a circuit to be completed from the right side of secondary S2 through CR4, CR3, connectors 115, 116 to SCRI, connectors 117, 118 to the grounded side of the motor; from the positive side of the motor through RFCI, connector 110 to the left side of S2. Thus, when SCRl is on, motor terminal 120 is positive relative to motor terminal 121 and when SCR2 is on, motor terminal 120 is relatively negative.

I have also provided certain protecting features. When SCR2 is conducting, CR1 and CR2 will have equal voltage drops of approximately .6 volt. This provides a negative bias across SCRl to protect it from spurious triggering. C2 and C3 serve as a gate filter to reduce transients, which could cause unwanted triggering and provide a stabilizing elfect.

RFCI and C4 compose an RF1 network which reduces R.F. interference above 50 mHz. C1 reduces R.F. below 50 mHz. and reduces commutator ripple which can cause instability.

While the foregoing description .sets forth the prin ciples of the invention in connection with specific apparatus, it is to be understood that this description is made only by way of example and not as a limitation of the scope of the invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. An antenna rotator control system comprising an antenna means, a DC motor means, console power means to convert AC to DC, bridge means comprising first and second otentiometers, said console power including a DC circuit applying DC to each of the otentiometers, said console means including said first potentiometer and having a movable, positioning wiper, said second potentiometer having a stationary wiper and rotating means including a resistance element for said second potentiometer, said rotating means coupled to said antenna means for providing rotational movement to said antenna means, solid state motor control circuit means coupled to the respective wipers to determine and imbalance condition, said solid state motor control circuit means to apply positive or negative rectified AC respectively to said motor for moving said antenna means in a direction which is a function of the polarity of the rectified AC, said console power means include an AC source and first and second secondaries, said first secondary coupled to said DC circuit, whereby DC is applied to said potentiometers, said motor control circuit means applying, from the AC, supplied from said second secondary, positive, or

negative half-cycles to the DC motor to cause respective rotation in either direction, said solid state motor control means comprise dual control SCR means, each having a gate, commonly connected cathodes and an anode electrode, means to couple the wipers of each potentiometer of said bridge circuit means to said respective gate, stabilization and biasing means for said dual control SCR means coupled to said wipers including first and second series rectifiers coupled across the anode and cathode of the first of the dual SCR means with the common connection of said series rectifiers connected to said SCR gate, and third and fourth series rectifiers connected in opposite series relationship from said first and second rectifiers and across the second SCR, with the common connection of said third and fourth rectifiers connected to said second SCR gate, a pair of series capacitors coupled between the respective gates having their common terminal connected to the common SCR cathode and the common terminal between the second and third rectifiers, said second secondary being coupled to said motor through two paths, said first path including said second SCR and said first and second rectifiers, said second path including said first SCR and. said third and fourth rectifiers, said paths coupling to opposite terminals of said motor.

2. The system of claim 1 including radio frequency interference suppressing means coupled to said DC motor, whereby commutator ripple caused by high radio frequencies may be reduced.

References Cited UNITED STATES PATENTS 3,327,186 6/1967 Gregory et al. 3,329,945 7/ 1967 Deming. 3,355,640 11/1967 Lewis et al.

THOMAS E. LYNCH, Primary Examiner US. Cl. X.R. 318681

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