US3521130A

US3521130A - Sequential operating system

Info

Publication number: US3521130A
Authority: US
Inventors: Wayne E Davis; James R Anderson
Original assignee: ROBERT TRENT JONES Inc
Current assignee: COSEN JAMES R; ROBERT TRENT JONES Inc
Priority date: 1968-03-13
Filing date: 1968-03-13
Publication date: 1970-07-21
Anticipated expiration: 1987-07-21

Description

July 21, W70 w. E. DAVIS ET AL SEQUENTIAL OPERATING SYSTEM 3 Sheets-Sheet l Filed March 13, 1968 CONTROLLER FIG...1

I NVENTOR5 JAMES R. ANDERSON BY WAYNE E. DAVIS W,

ATTORNEYS Jply 21, 19 70" gl pgv s IETAL 3,521,130

SEQUENTIAL OPERATING SYSTEM Filed March 13,1968 3 Sheets-Sheet 2 1 CONTROLLER SECTOR sec'ron GENERATOR "GATE GATE INVENTORS JAMES R.. ANDERSON ATTORNEYS July 21, 1970 w. E. DAVIS ET AL SEQUENTIAL OPERATING SYSTEM 3 Sheets-Sheet 5 Filed March 13, 1968 J m m S NEV Y E A v D WA. m R 9 M Y B Y United States Patent 3,521,130 SEQUENTIAL OPERATING SYSTEM Wayne E. Davis, Pompano Beach, Fla., and James R.

Anderson, Sunnyvale, Calif., assignors to Robert Trent Jones, Inc., Montclair, N.J., a corporation of New Jersey Continuation-impart of application Ser. No. 645,222,

June 12, 1967. This application Mar. 13, 1968, Ser.

Int. Cl. H01h 47/14; A01g 27/00 US. Cl. 317-139 13 Claims ABSTRACT OF THE DISCLOSURE A system for operating a plurality of devices in sequence using a single pair of conductors. A series of fast chargeslow discharge resistance-capacitive control circuits sequentially energize portions of an essentially two-wire power circuit extending from a power source first to one device and then to other devices in the order of intended operation. Initial charging of one control circuit energizes a corresponding one of the devices to be operated and simultaneously prevents current fiow to devices at a greater line distance from the power source. Interruptions of current from the power source for intervals less than the time required for discharge of each resistance-capacitive control circuit sequentially advance the flow of power from one device to the next device in the order.

This is a continuation-impart of application Ser. No. 645,222, now abandoned, filed June 12, 1967 by Wayne E. Davis and James R. Anderson which is entitled Sequential Operating System.

This invention relates to a system for sequentially operating a plurality of devices in fixed or selective sequence using a single pair of conductors extending from a power source to each of the devices in the order of intended operation. The system, and variations of it, are of substantial economic advantage, particularly where there are a number of devices to be operated which are spaced apart at great distances. As an example, the system is useful for operating sprinkler valves to water the fairways and greens of a golf course.

This invention contemplates a circuit having a plurality of fast charge-slow discharge resistance-capacitive circuits, each arranged in a basic control unit for operating a corresponding device or group of devices. Each control unit may be produced as a unitary assembly that can be manu factured as an electro-mechanical unit or as a solid state transistorized circuit. In addition, hybrid systems incorporating a number of each type of control unit are also feasible. The choice of construction depends upon the particular application in which it is used.

One object of the invention is to provide a system for remotely operating a plurality of sprinkler valves in sequence for either the same or varying periods of time.

Another object is to provide a system for operating a plurality of devices in sequence using an essentially twowire power circuit.

A still further object of the invention is to provide a system for remote operation of a plurality of devices either in fixed sequence or in a manner which allows selective operation of several devices or a particular device.

A still further object of the invention is to provide control units for energizing in sequence groups of devices which may be connected into an essentially two-wire circuit extending from a power supply to first one and then sequentially to each of the other groups of devices.

"ice

Various other objects of this invention will become apparent from a consideration of the following detailed description and the accompanying drawings, like parts being identified by like reference numbers and letters throughout.

FIG. 1 is a schematic diagram of the system for operating a plurality of sprinkler valves;

FIG. 2 is a schematic circuit of an electro-mechanical control unit for practicing the invention;

FIG. 3 is a schematic drawing illustrating a solid state control unit for practicing the invention;

FIG. 4 is a graphic illustration of the sequential operation of the system of FIG. 1 by reference to line voltage versus time;

FIG. 5 is a schematic circuit diagram of one form of power source useful for practicing the invention;

'FIG. 6 is a block diagram of a centralized system which employs the invention; and

FIG. 7 graphically illustrates the time relationship of control pulses for the system of FIG. 6.

FIG. 1, of the drawings shows a plurality of sprinkler valves V, each of which is opened by energizing a corresponding one of solenoids S. An operating circuit for energizing the solenoids comprises a pair of wires or

other conducting means

10 and 11 supplied with low voltage direct current from power source 12. The power is applied to a plurality of control units 13 and to valve solenoids S by means of an essentially two-wire circuit which extends from the power supply, first to one control unit and corresponding valve solenoid, and then sequentially to other control units and their corresponding valve solenoids in the order of intended operation. The number of control units provided and required for the circuit shown in one less than the number of valves operated, or 11-1.

A controller 14 is employed to periodically interrupt the power supply or line voltage as applied across conducting

means

10 and 11 and, thereby, to step the system. The controller may be a simple manually operated switch but a preferred form of controller permits automatic interruption of the line current for predetermined times and at predetermined intervals. For example, a clock-operated stepping switch such as a Buckner Model 611E irrigation controller may be used. Its purpose and function, to interrupt the line current, is hereinafter explained in detail in connection with operation of the system shown in FIG. 1.

FIG. 2 illustrates a preferred form of electro-rnechanical control unit having essentially four terminal connections. An input terminal 20 connects the positive side of the D-C power source 12 through a normally closed relay to an output terminal 21. Input terminal 20 of the first control unit of the series connects directly to the power source 12 through conductor 10 whereas the input terminal 20 of subsequent control units in the series connects the positive side of the power source through the output terminal 21 of the preceding control unit in the sequence. A third or common terminal 22 of each control unit is connected to the negative conductor 11, or ground; and control terminal 23 connects with the device to be operated. In the embodiment shown, terminals 23 connect with one side of solenoid coils 24, respectively, each coil having its other side connected to negative conductor 11 or ground.

The circuit of each control unit more particularly comprises a capacitor 25 connected in series with a unidirectional current passing means, such as a diode 26, and a resistor 27, between

terminals

20 and 22. A second re sistor 28 (having a relatively higher resistance than 27) is in parallel with diode 26 and resistor 27, connecting the juncture between capacitor 25 and diode 26 to ter- 3 minal 22. A relay coil 29 also connects that juncture through diode 30. The values of

resistors

27, 28 and diode 26 are selected to develop in capacitor 25 a fast charging rate and a rleatively slower discharge rate.

Application of line voltage to the control unit rapidly charges capacitor 25 through diode 26 and resistor 27. Part of the charging current also flows through diode 30 to energize relay coil 29. The energized relay coil 29 opens the normally closed contactor 31 of a single-pole, double throw relay. The contactor 31 simultaneously closes normally open relay contact 32 and establishes both a holding current through diode 33 and relay coil 29 to terminal 22 and an operating current to terminal 23, thereby energizing solenoid coil 24. Terminal 23 and normally open relay contact 32 connect with negative terminal 22 through diode 34 to protect

contacts

31, 32 upon their opening.

Thus, the initial charging of capacitor 25 immediately energizes relay coil 29 to open the normally closed electrical connection between input and

output terminals

20, 21 of the control unit. This simultaneously disables subsequent control units, connects full line voltage across the corresponding solenoid coil 24 and directs a holding current through the relay coil to maintain this solenoid in operating condition.

An interruption of the line current, for a time interval insufficient to discharge capacitor 25 completely, breaks the holding circuit through the now closed but normally open contact 32. This interrupts the flow of current through relay coil 29 and solenoid coil 24, contactor 31 returning to its normally closed position shown in FIG. 2. But the slowly decaying capacitor discharge current prevents the relay from reopening upon reapplication of full line voltage during that interval and, thus, full line voltage passes through the closed relay to the succeeding control unit. On the other hand, an interruption of the line current for an interval of time sufiicient to permit complete discharge of capacitor 25 will, in effect, reset the control unit, and the reapplication of full line voltage will then cause the circuit to again function as previously described.

In the complete system of FIG. 1, therefore, a brief interruption of power (of duration less than the time for complete discharge of a control unit capacitor 25) advances the operating sequence by one control unit, the reapplication of power operating the next controlled device in the sequence and disabling those subsequent to it. But a longer interruption, one which is long enough for all charged capacitors 25 to fully discharge, resets the system. Reapplication of power then operates the first control unit in the series.

The following component values for the control unit of FIG. 2 are suitable for operating conventional Skinner irrigation valve coils on a 24-volt system:

Capacitor 25-100 mf.

Diode 26-1N34A Resistor 276.8K

Resistor 28-47K Relay (29, 31, 32)MR 201

Gordos Reed Diode

30, 33, 34-1N457A FIG. 3 illustrates a control unit made up with solid state components for operating the system in essentially the same manner as the control unit of FIG. 2. Here again, input terminal 40 connects either to positive conductor or to the output terminal of a preceding control unit, and output terminal 41 is connected with either the input of the next control unit or the operated device of the last device in the sequence. The negative or ground terminal of the control unit is 42 and the control terminal is 43.

This control unit comprises capacitor 45 connected in series with resistor 46 and a unidirectional current passing means, such as diode 47, between

terminals

40 and 42. Initial charging of capacitor 45 through resistor 46 and diode 47 places a positive bias on the base of a transistor 48 through base resistor 49. The collector of transistor 48 is connected to conductor 10, and its emitter connects to ground through resistor 50. The positive bias permits a pulse of current to flow through transistor 48. Simultaneously, current flows through resistor 51 connected between the emitter of transistor 48 and the base of silicon controlled rectifier 52. The bias applied to the base initiates a flow of current from terminal 40 through SCR 52 to control terminal 43, energizing solenoid coil 53. The flow of current through the SCR also places a positive bias on the base of switching transistor 54 through base resistor 55. This permits a flow of current through transistor 54 from terminal 40 to terminal 42, connected to its collector through resistor 56. The collector of transistor 54 also directly connects to the base of switching transistor 57, having its collector and emitter respectively connected to

terminals

40 and 41. A current flow through transistor 54 to ground places a positive bias on the base of transistor 57, prohibiting current flow through the latter.

The silicon controlled rectifier 52 and

transistors

54 and 57 function essentially the same as the electro-rnechanical relay in the control unit shown in FIG. 2. Placing an initial charge on capacitor 45 starts a flow of current through the SCR that energizes the solenoid coil 53 and interrupts the power to those control units and devices at a greater line distance from the power source. Although the flow of current through transistor 48 ceases after capacitor 45 is fully charged, the SCR continues to pass current to coil 53 and to place a positive bias on transistor 55 until the line current across

conductors

10 and 11 is interrupted.

A solid state control unit for operating a plurality of conventional Skinner irrigation valve coils on a 24-volt system may be made up with the following component values:

Transistors 48, 572N3567 Transistor 54-2N3538 SCR 52MCR2304-1 Diode 471N34A Capacitor 4510 Inf. Resistors 46, 561K Resistor 49-18K Resistor 501.5K

Resistor 51-10 ohms Resistor 554.7K

The control unit and system in which it is used also allows selective operation of a particular controlled device. This is done simply by making a series of short interruptions in the power to

conductors

10 and 11 to step the system until the desired control unit capacitor is charged and its controlled device operated. The interruptions may be done manually. But, as previously indicated, controller 14 may also be programmed to briefly interrupt the line current for the number of times necessary to select out a particular valve. In either case, brief interruptions of power advance the sequence of valve operation, while interruptions of power for intervals which allows the capacitors to discharge, reset the entire system. The particular duration of power interruption required to step or to reset the system is, of course, determined by the size of capacitors and resistors which make up the time delay circuit in the control units.

In those applications of the invention where it is desirable to step through the sequential system and oper ate a particular device without actuating preceding devices, it is often better to advance through control units, as described above, at a voltage lower than the threshold operating voltage of the valve solenoids S, for example. Upon reaching the particular device to be operated, the applied line voltage is then increased to the normal operating voltage required. In order not to upset or reset the charged capacitors, the voltage should be increased slow- 1y, allowing all preceding control unit capacitors on the line to take up their full charge. For the Skinner valves and control units described in connection with FIGS. 1 and 2, the sequence is preferably stepped at a 12 volt level, and the voltage is then increased to 24 volts to operate a particular valve.

FIG. 4 illustrates a representative time cycle for operating the system of FIG. 1 with either the control units of FIG. 2 or 3 and using a preferred form of power supply having a maximum voltage of 24 volts. The power supply in this instance is one that will cut back to half voltage for a brief period after each interruption and which then slowly increases until full voltage is attained. The curve of FIG. 4 is a plot of line voltage (as applied across conductors 10 and 11) versus time, and it particularly depicts the line current for operating the first and fourth control units only.

In the exemplary cycle of operation represented by the curve of FIG. 4, the line current is initially set to off or interrupted by controller 14 for a period of time T, sufiicient to discharge all control unit capacitors. Controller 14 is then operated, as for example by closing contacts in power source 12, to apply an instantaneous 12 volt line current across

conductors

10 and 11. The line current rises slowly after a brief delay T and increases until it attains a maximum operating voltage of 24 volts, the voltage desired for operating solenoids S of the sprinkler valve described. Although the capacitor of the first control unit 1 is immediately charged during the period T the associated solenoid and sprinkler valve will not be actuated until the threshold operating voltage is reached. (The threshold voltage for Skinner valves described above is about 16-20 volts.) Following the brief delay time, and after the threshold voltage is attained, the valve associated with control unit 1 is opened and remains open until the current is interrupted.

At the end of the period T the line current is interrupted by a series of three pulses, each interruption being for a period of time T a period sufficient for deactivat ing the solenoids but insuflicient to permit full discharge of the control unit capacitors. The brief period of time T (during which the current is reapplied) follows each interruption period T The time period T is preferably less than the period required for building up the line current to maximum operating voltage. Accordingly, neither of the solenoid valves controlled by

units

2 or 3 are actuated. The reapplication of line current after the third pulse interruption, however, increases in a manner previously described with respect to control unit 1 until the solenoid and sprinkler valve associated with control unit 4 are operated, and that valve remains open until the end of period T.;,. The gradual rise in the line voltage, from 12 to 24 volts, allows the control capacitor of control units 1 through 4, which have been previously charged and partially discharged, to pick up the full charge at the 24 volt level without upsetting the system.

In some applications, of course, the controlled devices may be operated momentarily without objection. In such instances, the stepping operation may be carried out at full line voltage. However, to avoid difficulties with the seating of sprinkler valves, it is desirable that the stepping function proceed at a value less than that which will operate the sprinkler solenoids.

FIG. 5 illustrates a power source which provides the desired voltage changing function described above. It includes a supply 60 of 24 volt D-C power; a low voltage circuit means 61 which supplies power at the 12 volt level across

conductors

10, 11; high voltage circuit means 62 for providing a slowly rising voltagewaveform from 12 volts to a 24 volt level; and relay means actuated by controller 14 to provide a reset interruption of long duration, stepping interruptions of shorter duration and the shaped change from the 12 to 24 volt operating level.

The power supply 60 comprises a step-down transformer 63 which reduces A-C line voltage to 24 volts; a

6 diode bridge including diodes 65a, 65b, 65c and 65d which rectifies the transformer output to D-C; and filter condenser 66. One side of the supply is grounded.

Transistor 67 having its collector connected to the positive 24 volt supply through resistor 68 normally supplies 12 volt D-C power across conductor 10 and D-C grounded conductor 11. The base is biased by direct connection to the emitter of transistor 69 which has its collector directly connected to the collector of transistor 67. A 12 volt Zener diode 70 in series with resistor 71 between ground and the base of transistor 69 regulates the bias on transistor 69 at 12 volts. Thus, when conducting, the emitter of transistor 67 delivers power at 12 volts to conductor 10 through normally closed relays 72, 73, which as hereinafter described, provide reset and stepping interruptions in the power supplied. Resistor 74 and condenser 75 bypass the emitter output to ground. Capacitor 77 connects the emitter and capacitor 78 connects the collector of transistor 69 to ground. Resistor 79 connects its collector to the juncture between base resistor 71 and Zener diode 70 and capacitor 76 connects that juncture to ground.

Both of

relays

72 and 73 are normally closed and connect power to conductor 10 as shown in FIG. 5. The coil of relay 72 receives periodic reset pulses from controller 14 through terminal 80. The control pulses open relay 72 to D-C ground and, thus, provide an interruption in the power supplied to

conductors

10 and 11 of a duration sufficient to reset the system as hereinabove described. The coil of relay 73, on the other hand, receives control pulses of shorter duration from controller 14 at terminal 81 which open relay 73 to ground and interrupt the power for periods of short duration for stepping the sequence of the control units.

The high voltage circuit means 62 on command of a control pulse through terminal 82 from controller 14 supplies 24 volt power across

conductors

10 and 11 with a waveform which has a slowly rising leading edge from the 12 volts supplied by circuit means 61, as shown in FIG. 4. Transistor 83 having its collector and emitter connected in common with those same elements of transistor 67 supplies the rising voltage on command through

relays

72, 73. The base of transistor 83 connects ground through resistor 84 and is biased by direct connection to the collector of amplifier transistor 85, the emitter of which connects directly to the 24 volt D-C supply. The collector of a second amplifier transistor 86 biases the base of transistor through resistor 87. Resistor 88 and capacitor 89 also connect the base of transistor 85 to the 24 volt supply. The emitter of transistor 86 connects ground.

Transistor 90 having its collector directly connected to the 24 volt supply biases the base of amplifier transistor 86 through its emitter resistor 91. Zener diode 92 connected from ground through resistor 93 to the 24 volt supply provides a 3.6 volt bias on the base of transistor 90 through

series resistors

94 and 95. Capacitor 96 connects the juncture of these two resistors to ground and is parallel with Zener diode 92. Capacitor 96 is normally charged but can be shorted and discharged to ground by the closing of normally open relay 97 in parallel with it.

The power source of FIG. 5 normally provides a 12 volt output through transistor 67 which may be inter rupted to provide the stepping function by control pulses supplied to relay 73 or the reset function by a longer control pulse supplied to relay 72. Then, when the sequence has been stepped to a particular valve which must be operated, controller 14 supplies a control pulse to terminal 82 which closes relay 97. It shorts out capacitor 96 to ground and the capacitor discharge varies the resulting bias on the base of transistor 90 and through it on transistor 86. Transistors 86 and 85 amplify and apply the discharge wave form to reduce the base bias of transistor 83. Transistor 83 then conducts and supplies 24 volts to conductor 10. Transistor 67 turns off. But the amplified wave shape of the discharging capacitor 96 retards the rise in the output voltage of transistor 83 so that capacitors in each preceding control unit can slowly pick up their charge to the full 24 volt level without upsetting the system.

Appropriate values for the circuit which is shown in FIG. are as follows:

Diode bridge 65a65d-Motorola MDA 9522 Transistors 67, 83-RCA 40316 'Resistor 68-2 ohms Transistors 69, 86, 902N35 67 Zener diode 70-

1N4744 Resistor

71, 87, 931K Resistor 74, 956.8K

Capacitor 66, 75, 76, 78, 96500 mf. Capacitor 77-l0 mf.

Resistor 79'680 ohms Resistor 8447K Transistor 85--2N1183 Resistor'8833 ohms Capacitor 89l00 mf.

Resistor 91-15K Zener diode 92-1N4729, 3.6 volts Resistor 944.7K

There are many ways in which more complex systems may be used to complement the basic control units and system described above. For example, the controlled devices may be grouped into gated sectors, each of which employs the sequential circuitry described. The gated sectors may be selectively opened, for example by a variety of command signals such as tones, varying pulse width, plus frequency, etc.

FIGS. 6 and 7 illustrate the invention employed in a centralized system wherein the controller 14 and pulse generating means, such as pulse generator 100, are housed in a central control station. At the command of controller 14' the pulse generator emits programmed pulse trains which

conductors

101 and 102 transmit to a series of remote sector gates 103 each of which sequentially or selectively operates one or more controlled devices grouped in the sector through a series (1, 2, etc. or 11, 12, etc. or 51, 52, etc.) of control units 13. The system employes two

control conductors

101, 102 and a common ground 104. Conductor 101 supplies sector gate stepping and reset signals to the series of sector gates 103. Conductor 102 supplies control unit stepping and reset signals for actuating the control units 13 in the several sectors. Each sector gate comprises essentially a control unit circuit similar to that in FIG. 2 or 3 in combination with a power source circuit similar to that of FIG. 5.

The controlled pulse generator 100 supplies to conductor 101 a series of long pulses 105 separated by short interruptions 106, as shown in FIG. 7, which step the sector gates 103 in the manner heretofore described for the control units of the system in FIG. 1. For this purpose each sector gate includes, for example, a control unit circuit 13 as shown in FIG. 2 with the circuit values modified to accommodate a stepping interruption of different (longer) duration than the stepping interruptions for the control units in the sectors. Thus, the pulse 105 charges a condenser comparable to 25 in the first sector gate 103; opens a normally closed contactor 31 to disconnect conductor 101 from sector gates subsequent to it in the series; and closes a normally open contactor 32 to conduct the pulse in conductor 101 as a holding current through a relay coil 29.

The relay coil in the control unit circuit of the first sector gate at the same time closes another normally open contactor that connects conductor 102 to the power source circuit in the sector gate which is similar to that shown in FIG. 5. The arrival of pulse 107 in conductor 102 opens a normally closed relay, such as 72 of FIG.

5, and interrupts power supplied by the first sector gate 103 to conductor 10 for a duration sufficient to reset all control units 13 grouped in the first sector (1, 2, etc.). The pulse in 102 also opens switching means, such as relay 97 of FIG. 5, to charge a capacitor 96 so that the sector gate power circuit will supply only 12 volts across

conductors

10 and 11 to the first sector control units.

If the controller program calls for operation of the first and fourth sprinklers in the first sector, for example, an operating interruption 108 in conductor 102 then enables relay 72 to close and connect 12 volt power of the sector gate power circuit to conductor 10 of the first sector. This actuates the first control unit of the first sector as is shown in FIG. 7 at 109. The same interruption enables relay 97 to close and switch capacitor 96 to ground. The power supplied then rises from 12 to 24 volts and operates the solenoid of the first sprinkler of the first sector. This sprinkler operates until stepping pulse 110 appears in conductor 102 to produce a corresponding stepping interruption 111 in conductor 10' which is of ditferent (shorter) duration than that of the gate stepping interruptions 106.

As is described in connection with FIG. 4, this first stepping interruption 110, 111, is sufficient to deactivate the solenoid of the first sprinkler valve but is insufficient to permit full discharge of the capacitor 25 in the first control unit of that sector. The brief interruption 112 in conductor 102 and the corresponding reapplication of power in conductor 10 of the first sector at 12 volts, as at 113, is less than the period required for complete discharge of capacitor 96. Accordingly, the power supplied does not rise beyond 12 volts and the solenoid valve of control unit 2 in the first sector is not actuated. The subsequent pulse 114 in conductor 102 and the corresponding interruption 115 in conductor 10' of the first sector steps the sequence to the third control unit. The following interruption 116 in conductor 102 and corresponding 12 volt pulse 117 in conductor 10 charges the capacitor of the third control unit but is not sufficient to actuate the solenoid.

Finally pulse 118 in conductor 102 and the corresponding interruption 119 in conductor 10' steps the sequence to the fourth control unit in the first sector. Interruption 120 in conductor 102 as in the case of interruption 108 is of sufficient duration to permit sector gate power supply to rise in voltage from the 12 volt to the 24 volt level as at 121 and operate the fourth solenoid valve in the first sector. It continues in operation in the example of FIG. 7 until the next sector gate stepping interruption 106 appears in conductor 101. This, of course, opens a contactor 32 in the control unit circuit of the sector gate and the other normally open contactor associated with it that heretofore had connected conductor 102 to the power source circuit of the first sector gate. This interruption 106 steps the gating sequence to the second sect-or gate. There is no further operation of control units or solenoid valves in the first sector. The general sequence as herein described for the first sector is repeated for the second sector, etc. depending on the program of controller 14.

After all programmed sprinklers in all sectors are operated, a reset interruption 122 in conductor 101 of longer duration than interruption 106 resets the sector gate control unit circuits as previously described in connection with FIGS. 1 and .2.

The pulse generator 100 in the embodiment of FIG. 6 provides two separate series of square wave pulses, one which forms the stepping interruptions 106 in conductor 101 for the sector gates and the other which supplies the shorter stepping pulses in conductor 102 and corresponding stepping interruptions for control units in the various sectors. The controller v14 superimposes on these continuous pulses interruptions or pulses of longer duration such as 107, 108, 120 and 121 to provide the valve 9 operating and stepping functions which were described in the example of FIG. 7.

Although one particular system and several embodiments of the invention have been illustrated and described, it is to be understood that various modifications and changes may be made without departing from the spirit of the invention or the scope of the attached claims, and each of such modifications and changes is contemplated.

We claim:

1. A sprinkler system having a plurality of normally closed sprinkler valves; a plurality of solenoids each for operating a corresponding one of said valves; a power source to energize said solenoids; a circuit for operating said solenoids to open said valves in predetermined sequence comprising an essentially two-wire conducting means for carrying current from said power source to first one and then to each of the other of said solenoids, a plurality of control units for selectively interrupting the flow of current through said conducting means be tween said solenoids, each of said control units having interrupting means for interrupting the flow of current through said conducting means to the solenoids of valves subsequent to it in said sequence, operating means responsive to the normal line current of said power source for operating simultaneously said interrupting means and the solenoid preceding said interrupting means, and a fast charge-slow discharge capacitive circuit that disables said operating means upon application of normal line current following a stepping interruption of short duration and enables it upon application of normal line current following a reset interruption of longer duration; and control means interrupting power from said power source with stepping and reset interruptions in accord with said predetermined sequence.

2. A sprinkler system according to claim 1 wherein said power source delivers normal line current at a low stepping voltage level following interruption by said control means for a time period at least commensurate with said stepping interruption and, subsequent to said time period, delivers power which slowly rises in voltage to a higher operating level.

3. A circuit for operating in predetermined sequence a plurality of electrically operable devices from a power source comprising an essentially two-wire conducting means for carrying current from said power source to first one and then to each of the other of said devices; a plurality of control units for selectively interrupting the flow of current through said conducting means between devices, each control unit having an interrupting means to disconnect said conducting means from those control units and devices subsequent to it in said sequence, operating means responsive to the normal line current of said power source for operating simultaneously said interrupting means and the device preceding said interrupting means, and a fast charge-slow discharge capacitive circuit that disables said operating means upon application of normal line current following a stepping interruption of current from said power source of short duration and enables it upon application of normal line current following a reset interruption of longer duration.

4. The operating current of claim 3 wherein the power source supplies direct current and each control unit includes a capacitor; a relay having normally closed contacts in series with said conducting means, and a relay coil in series with said capacitor, said capacitor and relay coil being connected across said conducting means with the charging current of said capacitor energizing said relay coil; and a holding circuit for said relay that is enabled during charging of said capacitor and disabled upon interruptions of power from said power source for stepping intervals insufiicient to fully discharge said capacitor.

5. The operating circuit of claim 4 wherein said relay includes a pair of normally open contacts which close and apply current to one of said devices when said relay coil is energized.

6. The operating circuit of claim 4 wherein said capacitive circuit including said capacitor delays full discharge of said capacitor for a time period greater than said stepping interruption.

7. The operating circuit of claim 3 wherein said control unit includes a normally conducting transistor having emitter and collector connected in series with said conducting means, a capacitor, and means activated by the full charging current of said capacitor for biasing the base of said transistor to terminate conduction of said transistor and the flow of current through said conducting means to those control units and devices subsequent to it in said sequence.

8. The operating circuit of claim 7 wherein the power source supplies direct current and said capacitive circuit including said capacitor delays full discharge of said capacitor for a time period greater than said stepping interruption.

9. A control unit for energizing only one of a number of electrically operable devices in a sequence relative to other devices of said number, and which may be connected into an essentially two-wire power circuit extending from an interruptable power source to first one and then sequentially to each other device in the order of intended operation, comprising an interrupting means that may be connected in series with one wire of the power circuit, operating means responsive to the normal line current of said power source for operating simultaneously said inter rupting means and the device preceding said interrupting means, and a fast charge-slow discharge capacitive circuit that disables said operating means upon application of normal line current following a stepping interruption of current from the power source of short duration and enables it upon application of normal line current following a reset interruption of longer duration.

10. The control unit of claim 9 wherein said interrupting means comprises the normally closed contacts of a relay; said operating means comprises the normally open contacts and the coil of said relay and a holding circuit between said normally open contacts and said coil; and said fast charge-slow discharge capacitive circuit is con nected to the coil of said relay.

11. The control unit of claim 9 wherein said interrupting means comprises a switching transistor; said operating means includes a controlled rectifier biasing the base of said transistor; and said rectifier is connected to said fast charge-slow discharge capacitive circuit to bias the base of said transistor to interrupt the current flowing therethrough when current fiows through said rectifier.

12. A power source including means for normally supplying power at a low stepping voltage level; means which upon command supplies power at a higher operating voltage level and simultaneously discontinues power supplied at said stepping voltage level; and voltage inhibiting means delaying the rise time of the power output from said low stepping to said higher operating voltage level.

13. A sprinkler system having a plurality of solenoidoperated normally-closed sprinkler valves grouped into at least two sectors; sector gate means for each sector; a first conductive means connecting said sector gates in series; each of said sector gate means having interrupting means for interrupting the flow of current through said first conductive means to the sector gate means subsequent to it in the series, operating means for simultaneously supplying power to the solenoids in its sector and its interrupting means, and a fast charge-slow discharge capacitive circuit that disables said operating means upon application of normal line current in said first conductive means following a stepping interruption of short duration and enables said operating means upon application of normal line current in said first conductive means following a reset interruption of longer duration; 21 second conductive means connecting in series the solenoids of each of said valves in a sector; a plurality of control units for selectively interrupting the flow of current through said second conducting means between said solenoids, each of said control units having interrupting means for interrupting the fiow of current through said conducting means to the solenoids of valves subsequent to it in said sector, operating means responsive to normal line current of said sector gate for operating simultaneously said interrupting means and the solenoid preceding said interrupting means, and a fast charge-slow discharge capacitive circuit that disables said operating means upon application of normal line current in said second conductive means following a stepping interruption of short duration and enables it upon application of normal line current in said second conductive means following a reset interruption of longer duration; and control pulse means for supplying interruptions of power in said first conductive means to step said sector 12. gate means in predetermined sequence and for supplying through said sector gate means stepping interruptions of different duration to said second conductive means to step the control units of said valves in each of said sectors and to operate the solenoids of each sector in a predetermined sequence.

References Cited UNITED STATES PATENTS 3,124,722 3/1964 Steiner 317-439 3,215,916 11/1965 Hermann 317139 X 3,232,317 2/1966 Fowler 317-141 X LEE T, HIX, Primary Examiner US. Cl. X.R. 30741, 154