US2982880A

US2982880A - Apparatus for operation of gasfilled multicathode character display device

Info

Publication number: US2982880A
Application number: US6054A
Authority: US
Inventors: Klipstein Donald Leroy
Original assignee: ILLINOIS TESTING LABORATORIES
Current assignee: ILLINOIS TESTING LABORATORIES; ILLINOIS TESTING LABORATORIES Inc
Priority date: 1960-02-01
Filing date: 1960-02-01
Publication date: 1961-05-02
Anticipated expiration: 1978-05-02

Description

May 2, 1961 D. l.. KLlPsTElN APPARATUS FOR OPERATION oF GAS-FILLED MULTICATHODE CHARACTER DISPLAY DEVICE Filed Feb. l, 1960 United States Patent @Hice s ,eme, ,

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This invention relates generally to system or apparatus for use with gas-lilled multi-cathode tubes and vmore Y particularly is concerned with a novel circuit or apparatus for Yuse in the operation of such tubes.

In recent years, the read-out of data from many elec tronic apparatuses has been achieved in the form of pulses or signals which are capable of driving some form of indicating device to give a visual display. For example, gaseous discharge tubes have been devised which have a` plurality of cathodes and one anode, the different sources of signal being connected to be applied to the respective cathodes to cause the cathode to glow as a manifestation of flow of current from that particular cathode to the anode. Such display devices are of several types, including those which have the cathode arranged in a conguration of a character, such as the characters 0 to 9 all arranged in parallel planes but aligned front to rear so that the viewer can only see the particularl cathode which glows, and including those in which the cathodes are arranged in a circle and comprise short lines or points cooperating with a circular scale provided externally of the tube.

The structure of such tubes is characterized by the provision of a glass envelope having one surface through which the characters are visible, containing the electrodes and an ionizable gas such as neon along with other inert gases, for example small amounts of krypton, argon, etc. The tube is inoperative unless the gas is ionized, and this requires an ionizing potential between a cathode and anode which exceeds that which is characteristic of the gas or mixture of gases. The potential is applied between the anode and that cathode which it is desired to display, the ionization of the gas causing a visible glow in the vicinity of the cathode which has been energized, the cathode necessarily being at a negative potential.

The manner of connecting such display devices into circuits has in the past involved the simple connection of the different input circuits to the respective cathodes and aiording a common return from the anode, but such circuitry assumes suflicient power to drive the cathodes. Where very low power is all that is available some form of amplification is required, but this assumes expensive proportions since most of the character display lamps have at least ten cathodes, so that the cost of a single amplier is multiplied ten-fold. Another problem which heretofore has not been solved economically has been v the isolation of cathodes one from the other to prevent more than one cathode from becoming energized when a signal is applied thereto. y

The primary object of the invention herein is to overcome the disadvantages which are alluded to above, and to provide apparatus for operating a multicathode character display device which utilizes extremely low power, which is simple in construction and operation, which is economical to manufacture and maintain, and which requires a very small number ofsmall and readily obtained components.

Other objects and advantages Will appear to those skilled in this art as the preferred form of the invention is explained in connection with a circuit diagram in which conventional symbols are used to designate the several parts. Obviously, modifications and changes can be made emitters.

without departing from the spirit or scope of the invention.

In the circuit diagram,` the gas-lled multi-cathode character display tube is designated V1 and it has the cathodes C-1, C-2, C-3 etc. through C-10 each of which may be in the form ot some display character, such as shown herein, comprising the characters 0, l, 2 etc. through 9. 'Ihe anode is designated A and symbolically extends the entire length of the tube V-1 to be available to collect the electrons flowing from cathodes. When a discharge occurs between any cathode and the anode, the cathode will glow and display the character in which configuration the cathode has been formed.

The anode A is connectedby way of the lead 22 to the anode supply B through a suitable limiting or ballasting resistor R-11 and the return conductor for the transistors is 24 which includes a high ohmage resistor R-12. The return conductor 24 comprises the common input lead for all of the control inputs which are shown at the bottom of the diagram and places a positive voltage on the The inputs in the diagram are numbered in accordance with the respective characters which it is desired to display, and representa source of input signal, which if energized will cause the particular cathode with which it is connected tov glow.

The negative terminal of the anode supply is connected by way of the lead 26 to each ofthe collectors of ten transistors designated Tr-l through Tr-10` which provide the necessary amplication and switching needed to operate each of the cathodes.

Each transistor is connected in the emitter follower conguration, with the input in effect applied between its emitter and base. The resistors R-l through R-10 com.

prise the biasing resistors and are chosen so that a small signal will be sul'licient to cause the respective transistors to conduct between emitter and collector. Thus, for example, if a signal of say one volt is applied between the input marked 4 and the common lead 24, the normally non-conducting transistor Tr-S will conduct because of flow of current from the emitter to the collector. The signal cannot affect any of the other transistors because of the diodes ID-1 to D-10. Astor the signal between lead 24 and the input 4, current may flow from 4 through the diode D-5 but the polarity of'the other diodes relative to D-S prevents any of the transistors but Tr-S from receiving a signal.

Once conduction is established through transistor Tr-S, current may flow through the lead 28, the diode D-15 and from the cathode C-S to the anode A. With the circuit completed as described, all of the voltage of B appears between Ithe cathode C-5 and the anode A (but for a small drop in the transistor Tr-S which is of no consequence). This enables the discharge to occur between cathode C-S and the anode A, which causes current to ow in the circuit described. Current will not iiow through any of the diodes but D-15 because of the polarity and hence, the energization of one cathode such as C-S will not aifect the others. 'Ihe flow of current is limited only by the resistor R-11 and will continue only so long as the signal is applied to the input of transistor Tr-S and that transistor lis conducting.

In eliect, the transistors Tr1 through Tr-10 are semiconductor switching devices in emitter-follower conliguration which are actuated by the signals which are applied to their respective bases. The voltage which is controlled by the transistors is that of the B supply which may be of. the order of volts, supplied either by a battery supply or by any suitable alternating current energized rectier circuit. Inv a' practical circuit, vthe multi-cathode character display lamp `comprises a lamp designated NUP-10\2, having lactual number conigurations for cathodes. The Vphysical characteristics of the circuit were as follows:

Transistors Tr-l through 'Fr-10 2N398 (p-n-p) Diodes D-1 through Dalt) 1N191 Y R-l through R- (each) 3300 ohms R-IL.V 15,000 ohms It-l2 150,00() ohms small space occupied and the economy of components,

as Well as the ability of the circuit to operate with extremely low voltages, the display lamp is thus rendered more iexible and utilitarian for read-outs whose signals are normally considered of insucient amplitude and power to drive such a device.

The circui-t which has been described has been successfully utilized, but can'be varied as to its circuit constants and in other minor details. The list of components above shows that the transistors Tr-l to Tr-10 are all of the p-n-p type, this being a great advantage because the present cost of such transistors is many times less than the cost of n-p-n type transistors. The circuit herein is also not obvious in view of the polarity requirements of the multi-cathode display devices and the inherent polarity characteristics of p-n-p transistors.

Some conception of the size of the apparatus can be obtained by considering that the entire structure, exclusive of the tube V-1 and the power supply B, but including a mounting wafer and all connections occupied a space lf/ inches wide, 31/2 inches long and 7/10 inch thick.

What it is desired to secure by Letters Patent of the United States is:

l. Apparatus for operating a gas lled multi-cathode display device from a plurality of signal inputs of relatively low power, said device having a plurality of cathodes and an anode and the inputs adapted to be connected to energize desired 'ones oi said cathodes, cornprising a potential source having one terminal thereof connected to said anode, a semi-conductor switching device comprising a p-n-p transistor connected between each cathode and the second terminal of the said potential source, and eachrswitching device having an input circuit and the inputs adapted to be connected to the respective input circuits, means for biasing each transistor to conduct only when there is a signal applied to its respective input, and means for isolating each cathode from one another to prevent any one signal from energizing other than the cathode connected to the transistor in the circuit to which said signal has been applied.

2. Apparatus as claimed in claim l in which the means `for isolating the cathodes comprises at least one unilateral conducting device in series connection between each of said cathodes and its associated transistor, the unilateral conducting devices all being polarized in the same direction.

3. ApparatusV as claimed in claim 2 in which at least an additional unilateral conducting device is connected in serieswith each of said input circuits whereby to prevent the application of a signal to one circuit from aiecting any ofthe others, all of said additional unilateral conducting devices being polarized in the same direction.

4. Apparatus for operating a glow lamp discharge dep-n-p transistor including a base, emitter and collector, a source of potential, a continuous connection from said anode through said source of potential and through the emitters and collectors of each transistor to the respective cathodes whereby each cathode forms one of said transistor circuits with one transistor, each transistor circuit normally being non-conducting whereby the connection including the cathode and anode of that circuit is open, an input circuit for each transistor including a connection across the base and emitter of the respective transistors adapted to have an input signal applied thereto, there being first biasing means `across each base and emitter, second biasing means for the emit-ters of each transistor, and said second biasing Vmeans being connected in said continuous connection, the transistors' each serving as a switching device and being rendered normarly non-conductive by said biasing means but being rendered conductive by means of a signal applied to the input of any one transistor circuit, whereby the cathode of that transistor circuit will glow.

5. Apparatus as claimed in claim 4 in which there is an isolating diode in series with the connection between each cathode and its respective transistor circuit to prevent any but` one cathode to be activated by a single signal. v Y

6. A glow-discharge circuit comprising, Aa multi-cathode tube having a plurality of cathodes and an anode, and each cathode adapted to be rendered glowing by the application of a signal thereto from a plurality of respective signal sources, a source of direct current potential having its positive terminal connected to said anode, l

a plurality of p-n-p transistors each having at least a base, an emitter and a collector, each cathode being connected to the negative terminal of said potential source through the emitter and collector of one of the respective transistors, the signal sources each being connected respectively to the base of a transistor and to one or" its other electrodes, a biasing connection from said potential source to all of the transistors, and a biasing resistor connected between each base and emitter circuit for rendering the respective transistor non-conducting unless a signal is applied thereto.

7. A circuit as claimed in claim 6, in which each cathode connection has an isolating diode therein, and each transistor has a second isolating diode in its input, and means are provided for ballasting the tube when discharge occurs.

8. In an apparatus for operating a gas filled multicathode display device from a D.C. source, a plurality of switching circuits, one connected to each respective cathode of said display device, each circuit including a p-n-p transistor connected in emitter-follower configuration, means for connecting a signal input to the base and emitter of said transistor, means for biasing said transistors from said source, and means for isolating the switching circuits one from the other.

9. In an apparatus for operating a gas-filled multicathode character display device from a D.C. source connected between the anode of said device and all cathodes, a plurality of switching circuits one each connected between the respective cathodes and said source, each circuit including a p-n-p transistor connected in emitterfollower conguration, means for connecting signal inputs to the base and emitterof each transistor respectively, means for biasing said transistors to operate in switching characteristic, and means `for isolating said circuits from one another.

l0. A structure as claimed in claim 9 in which said last mentioned means comprise series diodes in the cathode circuits and in the input signal connecting means.

References Cited in the file of this patent UNITED STATES PATENTS 2,722,649 Immel et al. Nov. 1, 1955 2,756,366 Maynard July 24, 1956 2,769,939 Williams Nov. 6, 1956 annu.