US3569936A - Visual indicator pulse supply apparatus - Google Patents

Abstract

A visual display device is provided with a plurality of individual display elements such as lamps which are individually controlled to be either lit or dark in order to collectively present a changing pattern of dark and lit lamps which defines the display. To this end, each element is supplied with a separate control signal which has first and second mutually exclusive values, one of which represents the ''''element-off'''' state, the other representing the ''''element-on'''' state. All elements are connected in parallel to the output of a power supply. The supply produces an energizing voltage which takes the form of a pulse train of equidistantly spaced unidirectional pulses of like amplitude and duration. As a result, this voltage, in periods between pulses, has a first value which is insufficient to light the elements and, during the periods in which the pulses are present, has a second and higher value at which the elements can be lit. However, during the periods in which pulses are present, only those lamps which receive control signals in the ''''element-on'''' state are lit and all other lamps are dark.

Description

United States Patent 72] Inventor Ronald W. Johnson Cherry Hill, NJ. [21] Appl. No. 774,360 [22] Filed Nov. 8, 1968 [45] Patented Mar. 9, 1971 [73] Assignee Ultronic Systems Corporation [5 4] VISUAL INDICATOR PULSE SUPPLY APPARATUS 5 Claims, 1 Drawing Fig. [52] US. Cl 340/169, 340/167, 340/171 [51] lnt.Cl H )4q l/3 2 H04 5/00 [50} Field of Search 340/167, 171, l69;328/115 [56] I References Cited I UNITED STATES PATENTS 3,196,283 7/1965 Flattu 328/115X 3,299,404 l/ 1967 Yamarone et a]. 340/171 3,339,180 8/1967 Garfield 340/169 3,346,742 10/1967 Aniano 328/115X 3,394,270 7/1968 Pollack 328/115X Primary ExaminerHarold l. Pitts Attorneys-Norman J. OMalley and Theodore C. Jay, Jr.

state. All elements are connected in parallel to the output of a power supply. The supply produces an energizing voltage which takes the form of a pulse train of equidistantly spaced unidirectional pulses of like amplitude and duration. As a result, this voltage, in periods between pulses, has a first value which is insufficient to light the elements and, during the periods in which the pulses are present, has a second and higher value at which the elements can be lit. However, during the periods in which pulses are present, only those lamps which receive control signals in the element-on state are lit and all other lamps are dark.

Patentd March 9, 1971 INVENTOR RONALD (4.) JO NSON WM/w ATTORNEY VISUAL INDICATOR PULSE SUPPLY APPARATUS BACKGROUND OF THE INVENTION Various electronic systems are adapted to receive information in the form of electrical equivalents of alphanumeric characters and to reproduce these characters in the form of a moving visual display, such as a moving ticker display used in reporting stock market transactions. I

Many such systems employ large numbers of individual display elements such as small neon type lamps which are arranged in rows and columns and are selectively lit and darkened to produce the display.

Conventionally, each lamp is connected in series with the collector-emitter or drain-source path of a corresponding transistor. A fixed voltage from a power supply is applied across each series network so formed. In addition, a separate gate is associated with each series network. The output of each gate is connected to the control terminal or gate of the corresponding transistor. Each gate has two inputs. One input of each gate is connected through a corresponding status switch (which is an electronic on-off switch) to a terminal maintained at a fixed potential of given polarity. The other input of each of these gates is connected through a single control switch (which is also an electronic on-off switch) to a terminal maintained at a fixed potential of opposite polarity. When the control switch is open, all lamps are dark; when the control switch is closed, only those lamps associated with status switches which are then closed are lit and all other lamps are dark.

Thus, the rate at which the control switch is opened and closed determines the duty cycle of the lamps and thus the rate of change or timing of the display, while the number and relative position of the status switches which are opened and closed determines the pattern of the'display, the pattern changing as the status switches are opened and closed.

SUMMARY OF THE INVENTION In my invention, each lamp is connected in series with the collector-emitter or drain-source path of a corresponding transistor to form a series network as described above. However, instead of applying a fixed voltage across each network, I apply thereto a pulse train of I equidistantly spaced unidirectional voltage pulses of like'amplitude and duration whereby the voltage, in the period between pulses, has a first value which is insufficient to light the lamps but, in the periods when pulses are present, is periodically raised to a second value which is sufficiently high to light the lamps. The control electrode or gate of each transistor is connected through a corresponding status switch (which is an electronic on-off switch) to a terminal maintained at a fixed potential.

In the periods between pulses, all'lamps must remain dark. During the periods when pulses are present, each lamp is either lit or dark depending upon the state of the corresponding status switch.

As a result, my invention results in a display having the same visual effect as previously obtained, but, at the same time, eliminates one gate for each lamp used. My invention has the additional advantage of permitting the waveform to be limited whereby the bandwidth of these pulses is reduced and deleterious high frequency radiation is eliminated.

BRIEF DESCRIPTION OF THE DRAWING The accompanying FIG. is a circuit diagram of one embodiment of my invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the accompanying FIG., an alternating voltage, for example, a l volt, 60 Hertz, single phase voltage is applied across the primary winding of transformer 32. The secondary winding is connected to a full wave rectifier and filter whereby a direct voltage of selected constant value is produced at the output thereof. The output of filter 30 is connected to the collector of transistor 28. The emitter of this transistor is connected to terminal 34. Terminal 34 is connected to ground via series connected resistors 14 and 16. A plurality of series circuits are connected in parallel between terminal 34 and ground. Each circuit contains a neon lamp 10 connected in series with the collector-emitter path of a corresponding transistor 12. The base of each transistor 12 is connected through a corresponding electronic status switch 38. When switch 38 is activated, the corresponding transistor is rendered conductive; when switch 38 is inactivated, the transistor is cut off.

The base of transistor 28 is connected to the output of amplifier 26. The input of this amplifier is grounded via a bandwidth limiting network consisting of capacitor 22 and resistor 24 in series connection and is also connected to the collector of transistor 18. This collector is connected to a point of positive potential through a load resistor 40. A second load resistor 42 connects this point of positive potential to the collec-' tor of transistor 20. The emitters of both transistors 18 and 20 are grounded through a common resistor 44.

The base of transistor 18 is connected to the junction of resistors l4 and 16. The base of transistor 20 is connected through resistor 46 to a source of 'a constant positive voltage which serves as a reference and is also connected to a signal generator 36. Generator 36 delivers a voltage pulse train of equidistantly spaced, positive-going, rectangular pulses of uniform amplitude and duration.

The apparatus described above functions as follows. The

' current flowing in the emitter-collector path of transistor 28 and supplied to the various series circuits of lamps 10 and transistors 12 is pulsating and defines a pulse train of equidistantly spaced pulses of like waveform, amplitude, polarity and duration as shown. These pulses are trapezoidally shaped, i.e., have sloped leading and trailing edges, and thus are limited in bandwidth as compared to the rectangular pulses with substantially vertical leading and trailing edges produced by generator 36. This limitation is introduced via the network-of capacitor 22 and resistor 24.

During periods between current pulses, the current flowing through terminal 34 is low and all lamps are dark. During periods at which this current attains a high value as represented by the flat portion of each pulse, each lamp associated with a closed status switch willbe lit. Those lamps associated with open status switches will remain dark.

Resistors 14 and 16 function as a sampling network to supply a voltage proportional to that appearing at terminal 34 as a first input to a comparator constituted by transistors 18 and 20. The second input to the comparator receives a voltage which, when the pulses from generator 36 are absent, is proportional to the reference voltage alone and, when these pulses are present, is proportional to the sum of the reference voltage and the generator pulses.

The function of the sampling network, comparator and amplifier is to develop an error signal whenever the current flowing through terminal 34 varies from the desired values and to supply this signal to the transistor to vary the current gain in such a direction as to restore the current to the desired values.

While I have shown bipolar transistors in the drawing, it will be obvious that any other type of transistor can be used instead.

While I have described my invention with particular reference to preferred embodiments, my protection is to be limited only by the scope of the claims which follow.

Iclaim: 1. Apparatus for producing a pulse train of equidistantly spaced unidirectional current pulses of like amplitude and duration, said apparatus comprising:

firstvmeans to produce a first direct voltage of nominally constant value;

first and second output terminals, the second terminal being connected to said first means, said current pulses appear ing across said terminals;

tion coupled to said other comparator input.

2. Apparatus as set forth in claim 1 wherein said second means includes an amplifier.

3. Apparatus as set forth in claim 2 wherein said amplifier is provided with a bandwidth limiting network which causes said current pulses to be trapezoidally shaped.

4. Apparatus as set forth in claim 3 wherein said sampling means is a voltage divider network.

5. Apparatus as set forth in claim 4 wherein said first means includes a source of alternating voltage, a full wave rectifier and a filter.

Claims (5)

1. Apparatus for producing a pulse train of equidistantly spaced unidirectional current pulses of like amplitude and duration, said apparatus comprising: first means to produce a first direct voltage of nominally constant value; first and second output terminals, the second terminal being connected to said first means, said current pulses appearing across said terminals; a transistor having its collector-emitter current path being connected between said first means and said first terminal; sampling means connected between said first and second terminals; a comparator having two inputs and an output, one of said inputs being connected to said sampling means; second means coupling said comparator output to the base of said transistor; a source of a constant reference voltage of selected polarity coupled to said other comparator input; and a generator of rectangularly shaped equidistantly spaced unidirectional voltage pulses of like amplitude and duration coupled to said other comparator input.

2. Apparatus as set forth in claim 1 wherein said second means includes an amplifier.

3. Apparatus as set forth in claim 2 wherein said amplifier is provided with a bandwidth limiting network which causes said current pulses to be trapezoidally shaped.

4. Apparatus as set forth in claim 3 wherein said sampling means is a voltage divider network.

5. Apparatus as set forth in claim 4 wherein said first means includes a source of alternating voltage, a full wave rectifier and a filter.

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