US3076185A - Annunciator system - Google Patents

Description

Jan. 29, 1963 E. s. IDA ANNUNCIATOR SYSTEM Filed March 22, 1960 m A mm 6 V n: m m m Q40 D E 926. W mezzo: an 169 Y B n 26m mobzoz w 516 E $2.0m motzoz 5:6 9

8261 motzoz NEED OF ATTORNEY United States Patent Ofiice 3,076,185 ANNUNCIATOR SYSTEM Edward S. Ida, Mihnont Park, Pa., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Mar. 22, 1960, Ser. No. 16,775 3 Claims. (Cl. 340-213) This invention relates to an improved electrical annunciator, and particularly to an annunciator utilizing only a single transistor as the key component.

With the increased complexity in manufacturing operations, there is a growing need for more or less continuous surveillance of a multiplicity of operating conditions simultaneously, and this has led to a proliferation of independent sensing circuits each of which is adapted to monitor, or in some instances directly effect, a specific process step. It is imperative that management have positive assurance at all times as to the moment-by-moment status of each individual operating condition as sensed by the associated monitor circuits, which often total hunreds or even thousands of points, as the individual circuits are customarily called. Annunciator circuits fulfill the need of checking the operation of single points. It will be appreciated that simplicity of design of these annunciators is of prime importance, since even low cost units aggregate to very large sums when a great number of points must be serviced. At least of equal importance is the provision of high reliability in the annunciators, because absolute trust must be placed on the devices for the instant ascertainment of the operational status of the entire manufacturing establishment.

An object of this invention is to provide a very low cost annunciator using few parts, and these of extremely high proven reliability. Other objects of this invention are to provide an annunciator circuit using very little electrical power, one which is compact and occupies a very small space and one which can be conveniently substituted in toto if replacement or repair should ever become necessary. The manner in which these and other objects of this invention are attained will become evident from the detailed description and the drawing, which shows schematically a preferred embodiment of annunciator according to the invention.

Generally, this annunciator comprises in combination an alarm lamp connected across a power source preselected to operate the lamp at a first characteristic level of illumination below full brilliance, an auxiliary power supply circuit including a transistor operating in the switching mode connected in shunt power supply circuit with the alarm lamp and a signal source in electrical circuit with the alarm lamp through the transistor preselected to supply electrical current in an amount sulficient to operate the alarm lamp at a characteristic second level of illumination brighter than the first level of illumi nation, and an alarm switch responsive in position to the state of the apparatus monitored adapted to activate the auxiliary power supply circuit when the apparatus monitored is out of service, or operating abnormally, and to tie-activate the auxiliary power supply circuit when the apparatus monitored is restored to service. Preferably, the annunciator is provided in addition with an acknowledgment circuit as well as an audible alarm circuit as auxiliaries to the basic circuit and this arrangement is shown in the drawing.

Referring to the drawing, the alarm switch 18 is operated by the apparatus monitored (not shown) as indicated by the schematic connection thereto provided with oppositely oriented arrow heads, switch 18 being adapted to open upon occurrence of an alarm condition in the apparatus or process step monitored. It is this event which the annunciator is designed to detect and this is 3,076,185 Patented Jan. 29, 1963 accomplished by providing an alarm lamp 10 which, in this instance, is a resistance lamp (typically 6 watts) connected across the and volt D.-C. power leads 38 and 36, respectively. A ballast resistor 11 of typically 3800 ohms is connected in series with alarm lamp 10 and this reduces current flow through the lamp under normal conditions, i.e., when alarm switch 18 is closed, to a level at which the lamp is illuminated at a characteristic low brilliance well below full value.

An auxiliary power supply circuit is connected through transistor 12 in shunt power supply relationship with alarm lamp 10, transistor 12, operating in the switching mode, being the agency which alters the normal lamp illumination to a characteristic different brilliance when alarm switch 18 opens under failure. Transistor 12 can typically be a P-N-P type 2N3 63 (168 milliwatt, 400 milliampere, 40 volt, maximum rating). The emitter element of transistor 12 is biased to cutoff by connection to the negative side of diode 31. In the simplest configuration diode 13 is omitted and alarm switch 18 is connected directly between the transistor base lead 23 and the power supply reference lead 37. It will be understood that any sign such as that set out in the General Electric Co.

Transistor Manual, 2d ed. (1958), p. 90, is entirely adequate. The flasher circuit obtains its power from the voltage drop across diodes 30 (typically a Zener diode type 1Nl775) and 31 or, alternatively, it can be provided with a separate power supply. The output of the flasher circuit is a square wave signal varying between 0 and 10 volts typically, and resistor 34 (typically 4700 ohms) is preselected to provide approximately 2 milliamperes base current drive to transistor 12. 'lwpically, the flasher circuit switches its output signal on and ofi about once per second. A single signal source can accommodate a very great number of points, and connections available for individual additional point powering are indicated generally at 35.

The central power supply for the entire apparatus, connected to leads 36 and 38, can be one of a wide variety of commercially available designs; however, that indicated generally at 32 is typical. As indicated schematically in the drawing. this power supply consists of a symmetrical network including two capacitors (typically 150 mfd., 150 working voltage), four rectifier diodes (e.g., 1Nl1l7 type), and four resistors (e.g. 5.6 ohms, 10 watt size) powered from the secondary winding of a centertapped v.l60 v. transformer, the primary of which is connected to the usual 115 v. A.-C. power lines.

The circuit as hereinbefore described is complete and operable, in that it is adapted to signal the existence of a failure of a point monitored by the concomitant opening of alarm switch 18, which it does by flashing lamp 110 from its normal low brilliance state to bright in rapid sequence as set forth in the detailing of operation. However, it is preferred to utilize an acknowledgement circuit adjunct, so that the operator can dispense with the annoyance of a flashing light signal while going about with his repair activity, yet retaining identification of the points at which failure has ocurred until the difficulties have been rectified and the alarm switch restores the annunciator to its original state.

A preferred type of acknowledgment circuit comprises an -NE77 neon triode 14, the anode of which is connected directly to the base lead 23 of transistor 12. The cathode of triode 14 is connected through resistor 15 to the negative lead 36 of the power supply and is also connected through resistor 16 and through diode 13 (typically a C.B.S. 1N38A) to base lead 23; Resistors 15 and 16 are typically of 15K ohm size in the circuit detailed. The grid of. triode 14 is connected through clamping resister .39 (typically 15 megohms) to the minus lead 36 of the power supply and the purpose of resistor 39 is to prevent false firing of triode 14. The grid of triode 14 is also connected through resistor 17 (typically 100K ohms) to the manually operated, normally open, springreturn acknowledgment switch 20 and thence to the plus power supply lead 38. As in the case of the signal source 29, a single acknowledgment circuit can, and usually does, serve a great number of individual points, and additional resistors 19 of the same value as resistor 17 are provided for each other point utilizing the acknowledgment circuit in common.

In operation, signal source 29 operates continuously to produce a square wave voltage signal. With alarm switch 18 closed the emitter 22 and (base 23 leads of transistor 12 are short circuited through the alarm switch 18 and diode 13 and the transistor is cut oil, i.e., nonconducting. This cut off condition is further assured by the voltage drop across diode 31. (typically a GE. silicon diode type 1Nl692) which possesses a voltage drop across its terminals of one-half to one Volt when in its conductive state. This conductive state is provided by current flow through Zener diodes 27 and 30 (e.g., lNl775 type) and limited by resistor 28 (typically 3300 ohms), which are connected in series circuit one with another between leads 36 and 37. Ths causes alarm lamp to glow steadily at a low brilliance level, typically one-half or one-third of full brilliance as an examtile.- The operator is thus advised that the point monitored is functioning normally. At this moment also, neon triode 14 is held below its firing potential of approximately 80 volts by the voltage divider consisting of resistors and 16, although the operative condition of the triode 14 can be ascertained at will by depressing acknowledgment switch 20, which then ignites triode 14 for as long as the switch is held closed.

Opening of alarm switch 18 upon occurrence of apparatus failure breaks the short circuit across transistor 12 and the transistor is thereafter immediately driven on and oil with each cycle of square wave voltage output from signal source 29. Alarm lamp 19 is continuously supplied with current through resistor 11, under which conditions the transistor 12 is required to supply only a diiterence current of about 17 milliamperes to drive the alarm lamp 113 to full brilliance. The typical transistor 12 hcreinbefore described has a current gain of about 50, therefore only about one-third of a milliampere of base drive current is required; however, it is preferred to utilize about 2 milliamperes base current to drive it Well into saturation. Transistor 12 thus operates as a switch having an operating potential of about 30 volts in the off condition, and very low power dissipation in either the on or off condition, reaching only about 100 milliwatts during switching. Thus, transistor 12 supplies a succession of current pulses to lamp 10, which flashes the lamp from dim to bright repetitively, and is thereby calculated to attract the operators attention to the existence of a failure in the operation monitored.

If the operator desires to discontinue the flashing ac tion of alarm lamp it), he merely closes switch 20, thereby applying positive potential to the grid of neon triode 14, which thereupon fires and remains in the conductive state, thus closing the electrical circuit through resistor 15 keeping transistor 12 conducting steadily. This causes lamp 119 to stop flashing, and it thereafter burns at a steady high brilliance level, which is its distinctive illumination corresponding to the acknowledgment phase of operation. An indication of the recent failure of the point is thereby preserved and, even if the operators attention is temporarily distracted, he can immediately ascertain the correct identity of unremedied failures when he is again free to return to repair activity.

The entire circuit is automatically restored to its initial state by reclosure of alarm switch 18, which occurs when the point returns to full elficiency. This immediately drops the otential at the cathode of neon triode 14 to below the maintaining potential of the triode, which thereupon ceases to conduct. Concurrently, closure of alarm switch 18 once again short circuits transistor 12, and alarm lamp 10 drops in brilliance to the low level standby condition until a new emergency arises, which then causes a repetition of the complete alarm cycle.

In addition to the visible alarm, it is often also desirable to provide an audible alarm to call the operators attention to an alarm condition. This is accomplished by providing diode 24 connected to the junction of resistors 15 and 16 and also to the audible alarm auxiliary, indicated generally at 26. Since the audible alarm can optionally also monitor a large number of other points, these connections are indicated with their additional diodes as 25. The audible alarm is indicated as being powered by the voltage drop across Zener diode 27, but this can be replaced by a separate power supply, if desired, in which case the alarm can be made to serve the additional function of causing the alarm to sound upon failure of the main power supply 32.

Conveniently, alarm 26 can consist of a transistor 42, which may be a type 2N265 connected in the emitter follower mode with respect to an audio oscillator 43 by tying the emitter and base elements together through resistor 44 (typically 22K ohms), the collector being connected direct to negative lead 36. Audio oscillator 43 can be a commercially available type, such as a model A02 of Electronic Research Associates, Cedar Grove, N.J., which provides the input for a power amplifier 45, typically a model TAS of the same vendor. The amplifier in turn powers a speaker 46, typically a 2 watt, 8 ohm coil.

In operation, Zener diode 27 is preselected to have its voltage drop slightly less than the voltage drop across resistor 15 when either alarm switch 13 is closed or neon triode 14 is ignited. In this situation diode 24 is in its blocked condition and no current fiows through the circuit of alarm 26, so that the alarm remains silient. This condition corresponds to the closed, i.e., normal, position of alarm switch 13, or to an. acknowledgment of an alarm condition as a result of the operator depressing acknowledgment switch 20. Upon the initiation of an alarm condition which causes alarm switch 15 to open, the voltage across resistor 15 drops to zero, because diode 13 cannot conduct in the reverse direction and neon triode 14 is not ignited. Diode 24 now becomes conductive and current flow occurs through the circuit of audible alarm 26. This causes a warning sound to be emitted through the loud speaker 46. This audible alarm continues until rcclesure of alarm switch 18, or manual momentary closure of acknowledgment switch 20, either of these events causing the voltage drop across resistor 15 to return to normal which, in turn, causes diode 24 to return to its blocking state and restores the alarm to silence. It should be mentioned that the internal circuit of audible alarm 26 is of relatively high resistance, so as to cause no appreciable current flow through resistor 15 when it is in operation.

A somewhat simplified alternative design of annunciator circuit according to this invention utilizes a lower wattage resistance lamp 10, or a 2 or 3 watt neon or argon glow lamp (typically an NE34 or an ARI), in place of the 6 watt filament lamp 10. The ballast resistor 11, properly sized, can then be connected directly to reference lead 37. In this case the power supply need only be large enough to supply the current necessary to fire the desired number of neon triodes 14 being employed. While the glow lamps are appreciably more expensive than filament lamps, their longer life expectancy can well justify their use. In addition, there is much less power wasted in ballast resistor 11, which loss can become appreciable if a large number of points are served. Moreover, this permits power supply 32 to be eliminated entirely and a 110 volt A.-C. source substituted, as the neon triodes 14 fire successfully on such a supply.

It will be understood that all of the elements necessary to be supplied for a single alarm point can be enclosed within a compact box 47 designated in broken line representation. All of the other components shown are common to a large number of individual alarm annunciator units and, therefore, the cost per point of these components becomes quite low if an appreciable number of annunciators are employed.

It will be understood that it is possible to substitute a type N-P-N transistor for the preferred type P-N-P transistor 12, but the power supply requirement is somewhat more complicated and, accordingly, this is less preferred. In addition, if desired, a signal source 29 of steady output, as distinguished from pulsating, can be employed, particularly where an acknowledgment auxiliary is dispensed with or modified to accommodate the substitution.

From the foregoing, it will be understood that this invention can be modified extensively without departure from its essential spirit, and it is therefore intended to be limited only by the scope of the appended claims.

What is claimed is:

1. An annunciator circuit comprising in combination an alarm lamp connected across a power source preselected to operate said lamp at a first characteristic level of illumination below full brilliance, an auxiliary power supply circuit including a transistor operating in the switching mode connected in shunt power supply circuit with said alarm lamp and a signal source in electrical circuit with said alarm lamp through said transistor preselected to supply electrical current in an amount sulficient to operate said alarm lamp at a characteristic second level of illumination brighter than said first level of iilumination, and an alarm switch responsive in position to the state of the apparatus monitored to operate said transistor to closed circuit state when said apparatus monitored is out of service and to operate said transistor to open circuit state when said apparatus monitored is re stored to service.

2. An annunciator circuit comprising in combination a resistance type alarm lamp connected across a D.-C. power source preselected to operate said lamp at a first characteristic level of illumination below full brilliance, a ballast resistor in series circuit with said alarm lamp and said power source, an auxiliary power supply circuit connected in shunt power supply circuit with said alarm lamp provided with a transistor connected in electrical circuit with emitter element to the reference side of a pulsating signal potential source, collector element to a point between said alarm lamp and said ballast resistor and base element to the other side of said pulsating signal source through an alarm switch adapted to open upon failure of the apparatus monitored by said annunciator, and a common ground connecting the reference side of said pulsating signal potential source and said power source.

3. An annunciator circuit according to claim 2 provided with an acknowledgment circuit comprising a three electrode gas discharge tube having its anode connected to said base element of said transistor, its cathode connected to the negative polarity side of said alarm lamp and also to said base element of said transistor through a diode element permitting current flow solely in the direction of said base element, and its grid in electrical connection with a shunt circuit across said alarm lamp, said shunt circuit being provided with a manually operated switch, the characteristics of said acknowledgment circuit being preselected so as to initiate firing through said gas discharge tube upon closure of said manually operated switch and to restore said gas discharge tube to its initial non-firing state upon closure of said alarm switch.

References Cited in the file of this patent UNITED STATES PATENTS 2,772,410 Logue et al Nov. 27, 1956 2,829,257 Root Apr. 1, 1958 2,922,148 Feldman et a1 Jan. 19, 1960 2,931,018 Tellefsen et al. Mar. 29, 1960 OTHER REFERENCES Publication: Service, Fig. 1, page 6, Tuning Indicators, by Heller, February 1941.

UNITED STATES PATENT OFFICE CERTIFICATE. OF CORRECTION Patezfit No, 3,076,185 January 29, 1963 Edward 5., Ida

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected be1ow.

Column 4, line 40, before "coil" insert voice line 46, for "-silient read silent Signed and sealed this 3rd day of September 1963,

(SEAL) Attest:

ERNEST w. SWIDER AVID L- LADD Attesting Officer Commissioner of Patents

Claims (1)

1. AN ANNUNCIATOR CIRCUIT COMPRISING IN COMBINATION AN ALARM LAMP CONNECTED ACROSS A POWER SOURCE PRESELECTED TO OPERATE SAID LAMP AT A FIRST CHARACTERISTIC LEVEL OF ILLUMINATION BELOW FULL BRILLIANCE, AN AUXILIARY POWER SUPPLY CIRCUIT INCLUDING A TRANSISTOR OPERATING IN THE SWITCHING MODE CONNECTED IN SHUNT POWER SUPPLY CIRCUIT WITH SAID ALARM LAMP AND SIGNAL SOURCE IN ELECTRICAL CIRCUIT WITH SAID ALARM LAMP THROUGH SAID TRANSISTOR PRESELECTED TO SUPPLY ELECTRICAL CURRENT IN AN AMOUNT SUFFICIENT TO OPERATE SAID ALARM LAMP AT A CHARACTERISTIC SECOND LEVEL OF ILLUMINATION BRIGHTER THAN SAID FIRST LEVEL OF ILLUMINATION, AND AN ALARM SWITCH RESPONSIVE IN POSITION TO THE STATE OF THE APPARATUS MONITORED TO OPERATE SAID TRANSISTOR TO CLOSED CIRCUIT STATE WHEN SAID APPARATUS MONITORED IS OUT OF SERVICE AND TO OPERATED SAID TRANSISTOR TO

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