Condition Warning Memory Circuit

Abstract

For use with a system for converting coded condition data to an analog signal corresponding to the condition, a memory type condition warning circuit having calibrating capabilities.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention may be used with a system such as described in copending U. S. application, Ser. No. 294,059 filed Oct. 2, 1972 by Moreines, et al. and assigned to The Bendix Corporation, assignee of the present invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to condition warning systems and particularly, to condition warning systems having memory characteristics. More particularly, the invention relates to condition warning systems of the type described for achieving the desired result by analog means instead of by the more complex digital means.

2. Description of the Prior Art

Altitude information transmitted in accordance with Publication 1010.51A (Aug. 3, 1971) issued by the Department of Transportation, Federal Aviation Administration, is converted to analog form as described in the aforenoted copending U. S. application, Ser. No. 294,059. Utilizing means for the analog data include systems for providing a warning when the altitude reaches some predetermined critical value. Prior to the present invention complicated digital apparatus has been used for this purpose. The present invention uses simpler analog apparatus for achieving the result at a lower cost, with fewer components and with reduced power requirements.

SUMMARY OF THE INVENTION

This invention contemplates equipment of the type described including a source of reference voltage and switching means connected to the source for applying the reference voltage to a resistor network to selectively provide a calibrating voltage. Means are provided for comparing an analog signal corresponding to a condition to the calibrating voltage and for providing an output in accordance with the comparison. A current flow control circuit having memory characteristics is affected by the comparison output for operating an alarm device when the analog signal is at a predetermined critical level.

One object of this invention is to provide a condition warning circuit having memory characteristics.

Another object of this invention is to provide a circuit of the type described which is of analog construction and has the advantages of simplicity, cost and space economy, and reduced power consumption as compared to digital equipment for the same purpose.

Another object of this invention is to provide a device of the type described which has calibrating capabilities.

The foregoing and other objects and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings wherein one embodiment of the invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for illustration purposes only and are not to be construed as defining the limits of the invention.

DESCRIPTION OF THE DRAWING

FIG. 1 is a circuit diagram of the invention.

FIG. 2 is a symbolical diagram indicating the status of an alarm device operated by circuitry as shown in FIG. 1.

DESCRIPTION OF THE INVENTION

With reference first to FIG. 1 an input signal source 2 provides a d.c. analog signal V.sub.i corresponding to a condition which may be, for purposes of illustration, the altitude of an aircraft. Altitude signal V.sub.i is applied through a resistor 4 to a noninverting input (+) of an operational amplifier 6.

A reference signal source 8 provides a reference signal V.sub.R which is applied through a switch 10 to one of the resistors 12-26 in a resistor network 28. For purposes of illustration, signal V.sub.R is shown as applied to resistor 16.

The output of resistor network 28 at a point 30 is applied to a dividing network 32 connected to the resistor network at a point 44 and including serially connected resistors 34 and 36, and which resistor 36 is grounded. A calibrating voltage V.sub.C is provided at a point 38 intermediate resistors 34 and 36 and is applied through a resistor 40 to an inverting input (-) of an operational amplifier 42.

Resistor network 28 is connected to voltage divider 32 at point 44, and at which point 44 there is provided a voltage V.sub.C.sub.+K, where K is a predetermined circuit constant commensurate with the level of signal V.sub.i at which a warning is desired as will hereinafter become evident. Signal V.sub.C.sub.+K is applied to an inverting input (-) of amplifier 6 and signal V.sub.i is applied to a noninverting input (+) of amplifier 42.

Amplifier 6 is connected at its output to a base element 46 of a transistor 48 through a resistor 50, a diode 52 and a diode 54 connected in series. Transistor 48 has a grounded emitter element 56 and a collector element 58 connected to an alarm device such as lamp 60 which is excited by the output of a d.c. excitation source 62. A grounded resistor 64 is connected intermediate diode 54 and base element 46 of transistor 48.

Amplifier 6 is connected at its output to a gate 63 of a silicon controlled rectifier 64 through a resistor 66 and a diode 68 connected in series. Silicon controlled rectifier 64 has an anode 70 connected through a resistor 72 to a source of positive direct current and a cathode 74 connected to a collector 76 of a transistor 78. Amplifier 42 is connected at its output to a point 84 intermediate diodes 52 and 54 through a resistor 80 and a diode 85 and is connected to anode 70 of silicon controlled rectifier 64 through resistor 80 and a diode 82 connected intermediate resistor 80 and diode 85. Amplifier 42 is connected at its output to a base element 86 of transistor 78 through a resistor 86 and a diode 88. Transistor 78 has a grounded emitter element 90.

A grounded resistor 92 is connected intermediate diode 68 and gate element 62 of silicon controlled rectifier 64 and a ground resistor 94 is connected intermediate diode 88 and base element 86 of transistor 78.

As shown in FIG. 2 and as will be next explained, the circuitry of FIG. 1 is effective for operating lamp 60 so that the lamp is: off at points (X) and (P) when V.sub.i = 0; off at points (a), (c), (m), and (O) when V.sub.i = V.sub.C.sub.-K ; on at points (b), (d), (n), and off at points (f), (j), (l) when V.sub.i = V.sub.C ; on at points (e), (g), (i), (k) when V.sub.i = V.sub.C.sub.+K ; and on at points (h) when V.sub.i is greater than V.sub.C.sub.+K.

The operation of the invention is such that when V.sub.i is equal to or less than V.sub.C.sub.-K, amplifiers 6 and 42 have an output and lamp 60 is off. When V.sub.i is equal to or greater than V.sub.C.sub.+K, amplifiers 6 and 42 have outputs, but the output of amplifier 6 overrides the output of amplifier 42 and the lamp is on. However, when V.sub.i equals V.sub.C amplifier 42 has an output and the lamp may be on or off depending upon the previous history of the device, and in this sense the invention has memory characteristics. If V.sub.i approaches V.sub.C from V.sub.i being equal to or less than V.sub.C.sub.-K, the lamp comes on when V.sub.i equals V.sub.C. If V.sub.i approaches V.sub.C from V.sub.i being equal to or greater than V.sub.C.sub.+K, the lamp will go off when V.sub.i equals V.sub.C.

With reference now to both FIGS. 1 and 2 the operation of the invention at points a-p in FIG. 2 is as follows:

a. When V.sub.i is greater than V.sub.C.sub.-K, amplifiers 6 and 42 do not have a positive voltage output. Therefore diodes 52, 54, 85, 82, 68 and 88 do not conduct, transistor 48 is off and lamp 60 is out.

b. When V.sub.i equals V.sub.C, only amplifier 42 has a positive output whereupon diodes 54 and 85 conduct, turning on transistor 48 and lamp 60. Diode 88 conducts turning on transistor 78 which arms silicon controlled rectifier 64.

c. When V.sub.i is equal to or less than V.sub.C.sub.-K, the operation described in (a) repeats.

d. When V.sub.i equals V.sub.C, the operation described in (b) repeats.

e. When V.sub.i equals V.sub.C.sub.+K, amplifier 6 also has a positive output whereupon diode 52 conducts and provides an additional output for maintaining transistor 48 on. Diode 68 conducts, turning on silicon controlled rectifier 64. When silicon controlled rectifier 64 is turned on or conductive, the output of diode 85 to transistor 48 is shorted by diode 82 through the silicon controlled rectifier and transistor 78.

f. When V.sub.i is equal to or less than V.sub.C.sub.+K, amplifier 6 does not have an output but amplifier 42 has an output whereupon diode 88 conducts for maintaining silicon controlled rectifier 64 conductive. Diode 85 remains shorted by diode 82 through silicon controlled rectifier 64 and transistor 78.

g. When V.sub.i equals V.sub.C.sub.+K, the operation described in (e) is repeated.

h. When V.sub.i is greater than V.sub.C.sub.+K, the operation described in (e) is again repeated.

i. When V.sub.i = V.sub.C.sub.+K, the operation described in (e) is again repeated.

j. When V.sub.i = V.sub.C, the operation described in (f) is repeated.

k. When V.sub.i = V.sub.C.sub.+K, the operation described in (e) is repeated;

l. When V.sub.i = V.sub.C, the operation described in (f) is repeated.

m. When V.sub.i equals V.sub.C.sub.-K, amplifiers 6 and 42 do not have a positive output, therefore diodes 52, 54, 85, 82, 68 and 88 do not conduct and silicon controlled rectifier 64 delatches. Transistor 48 is off and lamp 60 is out;

n. When V.sub.i =V.sub.C, the operation described in (b) repeats;

o. When V.sub.i =V.sub.C.sub.-K, the operation in (c) repeats;

p. When V.sub.i is less than V.sub.C.sub.-K, the operation described in (a) repeats.

It will now be seen that the aforenoted objects of the invention have been met. Operation has been achieved using simple analog apparatus instead of more complex digital apparatus. Moreover, the operation has been achieved at a lower cost, with less space and with less power than required by digital apparatus.

Although but one embodiment of the invention has been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes may also be made in the design and arrangement of the parts without departing from the spirit and scope of the invention as the same will now be understood by those skilled in the art.

Claims

What is claimed is:

1. For use with a system providing a signal corresponding to a condition, apparatus comprising:

a reference signal source;

means connected to the reference signal source and responsive to the signal therefrom for providing first and second calibrating signals;

means connected to the system and to the calibrating signal means for comparing the condition signal to the first and second calibrating signals and providing operating outputs in accordance with said comparison;

condition warning means; and

means connected to the comparison means and to the condition warning means for applying the operating outputs to operate the warning means when the condition signal is at a predetermined critical level.

2. Apparatus as described by claim 1, wherein the means connected to the reference signal means and responsive to the signal therefrom for providing the first and second calibrating signals includes:

a network including a plurality of resistors connected in parallel;

switching means connected to the reference signal source and selectively connected to one of the plurality of resistors for applying the reference signal through said resistor to provide the first calibrating signal at an output of the network;

signal divider means connected to the resistor network output and responsive to the first calibrating signal for providing the second calibrating signal; and

the first calibrating signal corresponding to the second calibrating signal plus a predetermined constant commensurate with the predetermined critical level of the analog signal.

3. Apparatus as described by claim 2, wherein the means connected to the system and to the calibrating signal means for comparing the condition signal to the first and second calibrating signals and providing operating outputs in accordance with said comparison includes:

first means connected to the system and to the resistor network for comparing the signals therefrom;

second means connected to the system and to the signal divider for comparing the signals therefrom;

the first and second means being ineffective for providing operating outputs when the condition signal is equal to or less than the second calibrating signal less the predetermined constant;

the second means providing an operating output when the condition signal equals the second calibrating signal; and

the first and second means providing operating outputs when the condition signal is equal to or greater than the first calibrating signal.

4. Apparatus as described by claim 3, wherein;

the operating output provided by the first means overrides the operating output provided by the second means.

5. Apparatus as described by claim 3 wherein the means connected to the comparison means and to the condition warning means for applying the operating outputs to operate the warning means when the condition signal is at a predetermined critical level includes a current flow control circuit, said circuit comprising:

first current flow control means connected to the second means and to the warning means for passing the operating output from said second means to operate the warning means; and

second current flow control means connected to the first means and to the first current flow control means and responsive to the operating output from the first means for maintaining the first current flow control means effective to pass the output from the first means.

6. Apparatus described by claim 3, wherein the current flow control circuit includes:

third current flow control means; and

fourth current flow control means connected to the first means and to the third current flow control means and affected by the operating output from said first means for latching third current flow control means conductive.