US2765426A - Cold cathode gas tube counting chain - Google Patents

Description

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ATTY.

United States Patent COLD CATHODE GAS TUBE COUNTING CI-LIN Alfred H. Faulkner, Chicago, lll., assignor to Automatic Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application February 4, 1953, Serial No. 335,150

2 Claims. (Cl. S15-84.5)

The present invention relates in general to counting chain circuits and in particular to improvements in the counting chain circuits employing cold cathode gas tubes.

Up to the present time various methods have been used for coupling the tube of one stage to the tube of the sueceeding stage and which have proved to be unreliable and expensive. In particular, reference is made to the utilization of gas tube diodes for coupling one stage of the counting circuit to the next stage. The use of gas tube diodes for coupling has certain undesirable features such as the increased cost and the allowance which must be made for variations in Voltage drop in the dierent tubes, both initially and during the operating life. In the new circuit disclosed herein, the gas diodes have been eliminated and non-linear resistors of the silicon carbide type have been inserted in the cathode circuit. Also, the various counting circuits in use at the present time use cold cathode gas tubes comprising four or more elements, one of which elements is employed for resetting the counting chain circuit to the initial setting. The use of an additional electrode in a tube is both expensive and unreliable. The novel resetting arrangement used in thisinvention eliminates the need for tubes containing more than three electrodes and provides more positive action.

The principal object of this invention is to provide a counting circuit comprising a plurality of stages, employing non-linear elements which are capable of providing triggering voltages of sucient magnitudes for driving the succeeding stages without any regard to compensation to be made for diierences existing in tube characteristics.

Another object is` to provide a novel circuit arrangement in conjunction with a key to provide a more perfect means for resetting the counting chain circuit to the initial value.

Other objects of the invention will become apparent upon a further perusal of the specification taken in conjunction with the accompanying drawing.

The drawing illustrates a schematic diagram of the circuit representing the counting chain comprising seven cold cathode gas tubes 110-170 and the associated registering circuit comprising the indicator lamps 118, 138, 158 and 178.

The counting circuit comprises, in this case, four stages; each consisting of two tubes except the last stage which contains only one tube, namely tube 170. The starteranodes of the tubes in each stage are interconnected through resistors, such as 131 and 141, to a conductor, such as line 132, which in turn connects to a junction of resistors 113 and 114 from which a positive triggering voltage is obtained for striking either of the tubes 130 or 140. The non-linear elements, resistors in this case, contained in the circuit are indicated by 113, 133 and 153. Capacitors 115, 135, 155 and 175 play an important part in keeping only certain tubes conducting in each stage during the triggering and resetting processes. Capacitors 11,5, 135 and 155 also serve to store a potential which is used to discharge across the resistors found in the Indicator lamp 118 Count l. Indicator lamp 138 Count 2. Indicator lamp 158 Count 4. Indicator lamp 178 Count 8.

The count indicated by each indicator is shown in parenthesis under each indicator lamp on the drawings. A count other than shown in the above table and beyond 8 will be indicated by the illumination of more than one indicator lamp in which case the summation of the counts represented by the above table will give the total count. The count of 15, for example, would be indicated by the illumination of all of the indicator lamps the summation of which is equal to 15. Other registering devices may be used besides the present arrangement and which would allow individual counts rather than summation counts up to 15 or more.

A brief description of the operation of the counting chain circuit is hereby presented in order to bring out the role of the non-linear resistors in the cathode circuits of the various tubes. Operation or the reset key 180 will cause a positive potential present at terminal 183 to be applied to the starter-modes of all the tubes, but only tubes 12), 140 and 160 will strike because their cathodes are connected to ground and not to the source of positive potential, as the cathodes or tubes 110, 130, 150 and 170 are connected via the line 195. The indicator lamps 118, 138, 158 and 178 will remain unaiected.

The iirst positive pulse, received over conductor 101 and condenser 102 and impressed at the junction of the resistors 111 and 121, will cause the starter-anode of the. tube to initiate the striking of tube 110. Tube 120 will go out because the point 126 is made more positive because of the positive potential due to conduction of tube 110 and existing at point 116. No changes occur in the other stages. A voltage of approximately 90 volts exists across both of the resistors 113 and 114, or 45 volts across each, and similarly across the capacitor 115 from point 116 to point 126. The voltage existing` across the cathode circuit of tube 110 from point 116 to ground is suicient to ionize the indicator lamp 118 thereby indicating a count of one. g

The second pulse received over lead 1.01 will be impressed at the junction of resistors 111 and 121 and will cause tube 120 to strike and cause tube 110 to become extinguished in the manner similarly described above for the rst pulse operation. Indicator lamp 118 1ike- Wise becomes extinguished. Upon striking of tube 120, a Voltage of approximately 90 volts exists across the resistor 123. Adding the voltage existent across the capaci-y tor 115 to that existent acrossthe resistor 123, presents a total of volts, approximately, existing from point 116 to ground, that is, 180 volts across both of the resistors 113 and 114. The resistor 113 is of the non-linear type which possesses resistive characteristics Which'vary exponentially with the changes in voltages impressed across it. In the present case, the resistance of the element 113 will change to a low value if the magnitude of the voltage is increased from a normal to an abnormal state, as here, from 45 volts across the resistor 113, to 90 volts. As a result,` the voltage drop across the resistor 114 will be higher than across the resistor 113 so that about 120 volts exist between the junction of resistors 113 and 11410 ground. This increased voltage is utilized to strike the iatented Oct. 2, 1956v 3 tube 130 in the next stage via the line 132. Indicator lamp 138 becomes ionized at the time of the striking of the tube 130 thereby indicating a count of two. Further operation of other components will be described hereinafter.

The use of a non-linear resistor in the manner described hereinbefore makes the circuit more reliable and independent of the variation in characteristics of tubes due to construction and to longevity of operation. it is possible to achieve various combinations of voltages for tube striking purposes by proper selection of resistors pr; sing the required characteristics.

To prepare the circuit for operation, the reset key 180 is operated momentarily. This transfers the cathodes of the gas tubes 110, 130, 150 and 170 to the positive supply terminal 183 by means of the line 1115 and the make contacts 181 of the reset key 130. The circuit established for each of the tubes will be similar to that established for the tube 110 which hereinafter is described: positive terminal 183 through the make contacts 181, over the 'line 105, and the resistors 114 and 113, to the cathode of the tube 110. This prevents the aforementioned tubes from striking because their cathodes are at the same positive potential as their plates. The indicator lamps connected across the cathode resistors of the aforo-mentioned tubes will also remain inoperative. The other three gas tubes 120, 140 and 160 are caused to strike because their associated starter-anodes are at a high positive potential with respect to the cathodes of the respective tubes. A typical circuit for one of the tubes, namely 120 can be traced from the positive terminal 183, through the make contacts 181, over the line 1115, through the resistor 103, over the line 112, and through the resistor 121 onto the starteranode of the tube 120. During this time the capacitors 115, 135, 155 and 175 become charged to the voltage existing7 at the supply terminal 183.

When the reset key 130 is restored, capacitor 115, the right plate of which is negatively charged, discharges electrons over the following path: from the right side of the capacitor 11S, through the resistor 123 to ground, from ground through the break contacts 182, over the line 105, through the resistors 114 and 113 to the left side of the capacitor 115. This raises the voltage at the starteranode of tube 130 above its normal value because of the iow of electrons at the junction of the resistors 113 and 114. But the cathode potential of tube 130 is also raised above its normal value due to the electron discharge of the capacitor 135 from its right side through the resistor 143 to ground, from ground through the break contacts 182, over the line 105, and through the resistors 134 and 133 to the left side of the capacitor 135. As a result, the tube 130 does not strike because the potential existing between its starter-anode and the cathode remains below the striking value. In similar manner the discharge of capacitor 155 through the resistors 163, 154 and 153 prevents the tube 150 from striking. Since the present circuit is not intended to count beyond 15, only one tube is provided in the last stage and no cathode coupling capacitor is provided therein. Capacitor 175 is provided however to maintain the starter-anode to cathode potential of tube 170 below the striking value during the time that the capacitor 155 is discharging through the resistor 154 and 153 following the restoration of the reset key 180.

To insure reliable operation of the counting chain circuit, the reset key 100 is provided so that the circuit may be prepared in the manner hereinbefore described. The reset key is also used to restore the counting chain circuit to zero during counting operation whenever a need arises therefor. If the circuit were not prepared beforehand, the impression `of a positive pulse, at the junction of the resistors 111 and 121, might trigger either of the tubes causing it to strike. Since it is requisite for proper operation that the first pulse shall strike the first tube, namely 110, this requirement is fullled by having the other tube, namely 120, alreadyin the state of conduction.

lThe pulses to be counted are admitted at the terminal 101 across the capacitor 102 and fed into the iirst stage comprising tubes and 120 and their associated circuits. The first positive pulse on the input causes tube 110 to strike. This causes an electron ow from ground through the cathode resistors 114 and 113, through the tube 110 and to the source of positive potential present at the terminal 183. The flow of electrons through the cathode circuit of tube 110 causes the cathode of the tube 120 to become more positive momentarily because of the coupling established by the capacitor 115. This results in the extinguislunent of the ktube 120, The vpotential across the resistor 114 is insufficient to cause the tube 130 to strike at this time because the existence of the positive potential at the junction of the resistors 113 and 114, and which is connected over line 132, and through the resistor 1311 to the starter-anode to the tube 130, is too low to cause a breakdown between the cathode and the starteranode of said tube. The potential existing at the point 116 during the conduction of tube 110 is sufficient to cause ionization of the neon indicator llamp 118 to indicate the first count. Resistor 117 limits the amount of current flow through the indictor lamp 118. At this time, the following tubes are in the state of conduction: 110, 140 and 160.

The second input pulse causes tube 120 to strike which then causes the tube 110 to become extinguished in like manner as previously described. Indicator lamp 118 also becomes extinguished. The voltage existent across the tube 110 during its conduction is approximately 60 volts; and the voltage across both of the resistors 113 and 114 is approximately 90 volts. During the conduction of the tube 110, the voltage existent across the capacitor is also 90 volts, the lett side of the capacitor being charged positively. At the instant that the tube 1.20 strikes, the cathode voltage of tube 110 increases to twice its previous value. As was stated before, the voltage across the capacitor 115 is approximately 90 volts and the voltage across the resistor 123 at the time of initial conduction of the tube 120 is also 90 volts. So in eifect two voltages are in series with each other so that a total of 180 volts exists across the resistors 113 and 114 so that the electrons ow from the right side of the capacitor 115, through the resistor 123 to ground, from ground through the break contacts 182, and through the resistors 114 and 113 to the left side of the capacitor 115. 1f the resistor 113 were a linear resistor, the voltage across the resistor 114 would also be doubled at this time. By choosing appropriate circuit constants, this twoto-one increase in voltage across resistor 114 can be used to trigger the tubes in the succeeding stage, but close tolerances are necessary with such a circuit arrangement.

A considerable improvement is obtained by selecting an appropriate non-linear resistor 113. If a Vsilicon carbide resistor, which has characteristics such that the voltage drop varies as the fourth root ofthe current, is used for example, the voltage drop across the resistor 114 will increase by a factor greater than 2 which latter factor was present when the voltage drops across the resistors 113 and 114 are equal initially. Thus the voltage across the resistor 114, and also across resistor 113 may be 45 volts each following the first positive pulse. The voltage at this time at the junction of the resistors 113 and 114, as previously described is below the .starteranode breakdown voltages of the succeeding stage. When the tube 120 strikes on the second positive pulse the voltage across the resistor V114 will increase to approximately 120 volts, which is sufcient to cause the tube 130 to strike, in as much as the starter-anode-to-cathode breakdown voltage is well below this figure. The voltage across the cathode resistors 133 and 134 is suiiiciently high to ionize the neon indicator lamp 138 thereby indicating the count of two. The ionization of tube will cause a more positive voltage to be present in the cathode circuit of the tube 140 thereby extinguishing it. The voltage across the resistor 113 will be approximately 60 volts at this time. A still greater improvement may be achieved by selecting a silicon carbide resistor having an exponent smaller than one-fourth. The result of the second positive pulse is that the tubes 120 and 130 are conducting together with tube 160 which was initially ionized by operation of the reset key 180. Indicator lamp 138 is also on.

The third positive pulse will apply a positive voltage across the resistor 111 onto the starter-anode of the tube 110 so that tube 110 will strike causing the tube 120 to become extinguished because of the raised cathode potential of said tube due to the coupling of the capacitor 115 to the tube 110 as previously described. The voltage existing at the junction of the resistors 113 and 114 is insucient to cause the tube 148 to strike, as was previously described, so that no change occurs in the second stage. At this time, tubes 110, 130 and 164) are conducting and indicator lamps 118 and 138 are illuminated thereby indicating a total count of three.

The fourth positive pulse will cause the tube 120 to strike with the consequence that an abnormally high positive voltage will exist at the junction of the resistors 113 and 114 which will cause the tube 148, in the second stage, to strike. Tube 120 and its associated indicator lamp 118 will become extinguished at this time. Striking of the tube 148 will cause an abnormally large positive voltage to be present at the junction of the resistors 133 and 134 and which is impressed across the line 152 to the starter-anode of the tube 150. Tube 1.30 and its associated lamp 138 will become extinguished at this time. Tube 158 will strike and, in a manner previously described for the other stages, will cause tube 160 to become extinguished. Upon striking of tube 150, indicator lamp 158 will go on. At this time, tubes 120, 140 and 150 are conducting and the indicator lamp 158 is lighted thereby indicating a count of four.

The operation of the counting chain circuit will be similar for each succeeding positive pulse and the method of operation for the full count, namely the count of 15, will not be fully described in this discussion. However, a briet` running description of operation for each count will be given to indicate the interplay of the tubes and indicator lamps.

The fifth pulse will cause tube 110 to become ionized and to cause the illumination of the indicator lamp 118. Tube 128 will become extinguished. At this time tubes 110, 148 and 150 are conducting and the indicator lamps 118 and 158 are on thereby indicating the total count of tive.

The sixth pulse will cause tube 120 to become ionized and cause the extinguishing of the tube 110 and its indicator lamp 118. Tube 130 will become ionized together with its indicator lamp 138. At this time tubes 120, 138 and 150 are ionized together with the indicator lamps 138 and 158; the latter indicating the count of six. Tube 140 became extinguished when tube 130 began to conduct.

The seventh pulse causes the tube 110 and its associated indicator lamp 118 to strike with the result that tube .120 becomes extinguished. At this time tubes 110, 130

and 150 are conducting together with their associated indicating lamps 118, 138 and 158 thereby indicating the total count of seven.

In order to illustrate the maximum use of the tubes contained in the counting chain circuit, a full description will be made of what transpires upon the receipt of the eighth positive pulse. Prior to the receipt of the eighth positive pulse, the following tubes and indicator lamps are in the state of conduction: 110 and 118, 130 and 138, 150 and 158. Application of the eighth positive pulse at the terminal 101 will cause tube 120 to strike and, in the manner previously described, will cause tube 110 and indicator lamp 118 to become extinguished. Striking of tube 120 will create an abnormally high positive voltage which will be developed at the junction of the resistors 113 and 114, and which voltage is impressed across line 132 and across the resistor 141 onto the starter-anode of the tube 140. Tube 140 will strike and, in a well known manner, cause tube and its associated indicator lamp 138 to become extinguished. The striking of tube 140 also causes an abnormally high voltage to be found at a similar junction, namely the resistors 133 and 134, and which voltage is impressed across line 152 and across the resistor 161 onto the starter-anode of tube 160 found in the next succeeding stage causing it to strike. The striking of tube 160 will extinguish tube and its indicator lamp 158 and will similarly cause an abnormally high positive voltage to be found at another similar junction, namely resistors 153 and 154, which voltage is impressed across line 172 and across the resistor 171 onto the starter-anode of the tube 170 found in the next succeeding stage, which in this case consists of only one tube. Application of the high positive voltage upon the starter-anode of the tube 178 will cause it to strike and also to light up the lamp 178. At this time the following tubes are conducting: 120, 140, and 170 with its associated indicator lamp 178. The lamp indicates now the total count of eight.

The ninth pulse will strike tube 110 and its associated indicator lamp 118 and cause the extinguishment of tube 128. No other changes result in the succeeding stages. rl`ubes 110, 148, 158 and 170 are conducting at this time. Indicator lamps 118 and 178 are on to indicate the total count of nine.

The tenth pulse strikes the tube 120 which causes tube 118 and the indicator lamp 118 to go out. The striking of tube 128 results in the striking of tube 138 and its associated indicator lamp 138. Tubes 120, 130, 160 and 178 are conducting at this time together with the indicator lamps 138 and 178 thereby indicating the total count of ten.

The eleventh pulse strikes tube 110 and indicator lamp 118 causing the extinguishment thereby of tube 120. At this stage, tubes 110, 130, 160 and 170 are ionized together with the indicator lamps 118, 138 and 178 to give a total indication of a count of eleven.

The twelfth pulse will strike tube 120 and result thereby in the de-ionization of tube 110 and its indicator lamp 118. The striking of tube 12() will cause the striking of tube 148 resulting thereby in the extinguishment of tube 138 and its indicator lamp 138. The striking of tube 148 results in the striking of tube 150 and its indicator lamp 158 and the extinguishment thereby of tube 160. Tubes 128, 148, 158 and 170 conduct at this time together with the indicator lamps 158 andl 178 thereby giving a visual indication of a total count of twelve.

The thirteenth pulse will strike tube 118 and its indicator lamp 118 thereby resulting in the de-ionization of tube 120. At this time, tubes 110, 140, 150 and 170 are ionized. Indicator lamps 118, 158 and. 178 are illuminated and indicate the total count of thirteen.

The fourteenth pulse will strike tube 12) resulting in the extinguishment of the tube 110 and its indicator lamp 118. Tube 138 and its indicator lamp 138 will become ionized thereby resulting in the extinguishment of tube 140. Tubes 128, 138, 150 and 178 are conducting at this time together with the indicator lamps 138, 158 and 178 to indicate a total count of fourteen.

In order to terminate this discussion in orderly manner, a full description of the operation will be given by describing what occurs upon the receipt of the fteenth positive pulse. Upon the receipt of the fifteenth positive pulse, tube 110 strikes and causes the indicator lamp 118 to light up and the tube 120 to become extinguished. The tubes in the other stages are not affected at this time. Tubes 118, 138, 158 and 170 are now conducting together with their associated indicator lamps 118, 138, 158 and 178. A total count of fifteen is indicated by said lamps. Receipt of further positive pulses will cause changes in all the stages except the last stage with the result that no more pulses can be counted beyond the number 15. In order to extinguish the counting tubes and the indicator lamps, it is necessary to reoperate the reset key 180.

As is clearly seen from the method of operation described hereinbefore, the effect of the odd numbered pulses is to effect a change in only the iirst stage comprising tubes 110 and 120. The even numbered pulses effect the striking of tubes in at least two stages thus indicating that it is only the even numbered pulse which effects control over the tubes beyond the first stage. The maximum number of tube activities that was seen to occur upon the receipt of an even numbered pulse, occurred during the receipt of the eighth pulse which caused the striking of four tubes, namely the tubes 120, 140, 160 and 170 and the indicator lamp 173.

The counting process may be repeated by operating the reset key 180 so that the positive potential present at terminal 133 is impressed across the make contacts 181 to the cathodes of all ionized tubes causing the latter to become extinguished. Tubes 120, 140 and 160 become conductive after each resetting. Similarly, the counting chain circuit may vbe reset to Zero from any intermediary count at which it may be resting. Application of vpositive pulses at the terminal 101 will cause the counting chain circuit to count the next series of positive pulses up to the maximum number possible with this arrangement.

While there has been described what is at present considered to be the preferred embodiment of the invention it will be understood that various modifications may be made herein and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a binary glow discharge tube counting 'chain comprising a plurality of stages, wherein each succeeding stage is triggered by an nterstage coupling pulse produced in response to every second operation of the immediately preceding stage, a irst and a ysecond tube in each stage, a load circuit for each tube, said load circuit for said rst tubes in each stage comprising a linear and a non-linear resistor connected in series, the discharge of the second tube of a stage causing an increased voltage to be impressed across said load circuit of said first tube, said non-linear resistor of said load circuit decreasing in resistance in response to said increased voltage to thereby increase the voltage across said linear resistor, the succeeding stage connected to the junction of said two resistors, whereby the increase in amplitude of said latter voltage causes the triggering of the said succeeding stage.

2. A counting chain as claimed in claim l wherein said non-linear resistor has a characteristic such that the voltage drop varies as the fourth root of the current.

References Cited in the le of this patent UNITED STATES PATENTS 2,562,591 Wagner et al. July 31, 1951 2,577,075 Dickinson Dec. 4, 1951 2,583,102 Holden Jan. 22, 1952 2,620,440 Baker Dec. 2, 1952 2,626,751 Mullarkey Jan. 27, 1953 2,630,969 Schmidt Mar. 10, 1953 OTHER REFERENCES Cold Cathode Glow Discharge Tubes and Associated Circuits by G. H. Hough and D. S. Ridler, pp. 230, 231, May 1952, Electronic Engineering.

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