US2432292A - Electronic counter circuit - Google Patents

Description

H. B. DEAL ELECTRONIC COUNTER lGIRGUI'I Filed lay 29, 1943` .Qnlwwm qu nos. lvl l l wn QEG la uwb Skin Patented Dec. 9, 1947 ELECTRONIC COUNTER CIRCUIT Harmon B. Deal, Glen Ridge, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application May 29, 1943, SerialNo. 489,102 6 Claims. (Cl. Z50-27) This invention relates to electronic counter cir- :uits andhas particularly to do with the proislon of a device of such character that it operates substantially as a frequency divider for delivering in an output circuit one pulse following a succession of input circuit pulses of any predetermined number.

Frequency dividers are well known in the art. These frequency dividers are often used for counting purposes. Difficulties have arisen in the past if it is attempted to count accurately a large number of pulses from a given source. When a counter is set up to divide by two, the tolerances of critical voltages in the circuit parameters are very great. For division by three, the tolerances are reduced. As thenumber of input pulses is increased, the tolerancesd are reduced more and more. Counts up to thirty or thirty-five have been obtained, but the tolerances have been so close that no dependence can be placed on the results. It has, therefore, been a practice to split the count into two or more stages.-`

Thus a count of 50 might be obtained by first counting ve pulses, and then in the second stage counting ten pulses. As another example, a count of 49 might be obtained in successive stages in which seven and seven are counted.

It is obvious that where two stages of countlng are employed, the divisor used in each stage must be one of two factors of the number to be counted. Hence it would be impossible to count a prime number in this manner, i. e. in two steps or stages, since the number itself is unfactorable.

It is an object of my invention to provide an electronic circuit arrangement for frequency division or counting of pulses wherein the operation is substantially independent of frequency and may be controlled by pulses which are apcriodic.

It is another object of my invention toprovide a system of the class described in which the counting of pulses is not adversely influenced by voltage variation within wide limits occurring' in any of the circuit parameters.

It is another object of my invention to provide a system of the class described in which frequency division may be obtained by the use of a single stage possessing two alternate ratios of sub-division, whereby the units of a prime num..l v

berh of relatively high order may be counted, as well as any factorable number.

It is another object of my inventionto provide an electronic 'counter which is substantially aperiodic in action.

It is stili another object of my invention to proj vide an` electronic counter forcountlng a rela- 2. tively large but unfactorable number of pulses. Again, it is an object of my invention to provide an electronic counter such that after counting a predetermined number of pulses in a given series, a different predetermined number of following impulses of that series may be counted, thus producing a summation of the two counts.

My invention will now be described in more detail, reference being made to the accompanying drawing, in which:

Fig. 1 shows a relatively simple circuit arrangement for electronic counting purposes;

Fig. 2 shows an alternative circuit arrange- 'ment for substitution in the complete circuit of Fig; 1, the modification being disposed to the right of a. dividing line a-a;

Fig. 3 shows a more elaborate circuit arrangement for pulse counting purposes in which means are provided for counting any number of pulses, even though it be a prime number; and

Fig. 4 shows a diagram `ci voltages produced over a period of time in a counting circuit, such as that of Fig. 3.

Referring first to Fig. 1, I show an electron discharge tube i which is preferably of the tetrode type having a cathode 2, a, control grid 3, a screen grid 4, and an anode 5. This tube is provided with an input circuit including a resistor 6 which is .connected between the grid Sand the cathode 2. Input pulses from any given source may be impressed across the capacitor 'l for controlling the tube I.

The screen grid 4 is preferably maintainedy at the full positive potential of the operating source, While the voltage applied to the anode 5 is varied with the tube impedance, since the anode current is conducted through a resistor 8 in the output circuit.

VPulses of input potential are amplied by tube i and impressed across a capacitor '9 for conduction to ground through a twin diode rectier tube i0. Full-wave rectification takes place in this tube in the usual manner. Half waves of one polarity of output from the tube l traversev 'I'he eiects of the successive impulses which are amplied in the tube i are, however, such as to build up a charge on capacitor Ll until it reaches a critical value. The build-up time is determined by several factors including the values assigned to capacitors il and 9 respectively, the value of a cathode resistor I2 which is provided for an electronic tube I3 of a following stage, and the adjustment of a tap 22 on a potentiometer 2l for controlling the bias on a grid 20 in a tube Il.

Tube i3 may, ii desired, be a simple triode. Its circuit arrangement is, however, peculiar in that it possesses no grid leak connection between its control grid I4 and its cathode I5. The space path between the grid I4 and the cathode I5 is, however, influenced by the charge on capacitor I I and is, in effect, used as a discharge path for the capacitor II after the grid voltage has been raised to a critical value.

Discharge tubes I3 and I1, both triodes, are disposed in the relationship of multivibrator tubes in order to produce a see-saw action, the time constant of which is made dependent upon the summation of incremental charges on capacitor II where each successive increment is made up of an individual transfer of charge from the capacitor 9. Such individual charges are conducted through the space path d1 in the rectiiier tube I0.

Tube I'I possesses an anode I8, a cathode I9, and a grid 20. Anode potential derived from a source indicated as +B is applied through resistor 23 to the anode I6 in tube I3, also through resistor 24 to the anode I8 in tube I1. The cathodes I5 and I9 in the respective tubes I3 and II are interconnected and have a common cathode resistor I2 leading to ground.

A potentiometer 2i is connected between the anode i6 of tube I3 and ground. It has a tap 22 which is connected to the grid 20 in tube I1.

In the operation of the circuit arrangement of Fig. 1, let it be assumed first that a negative pulse is applied across capacitor 'I and resistor 6, such that grid 3 in tube i is biased to cutoff. Since no current would then now in the tube I, there would be no appreciable potential drop in resistor 8. The full +B voltage would, therefore, be applied to capacitor 3 for charging the same. The surge impulse which develops this charge traverses the space path d1 in tube Iii and applies a limited charge to capacitor II which is of a higher microfarad rating than capacitor 9.

, Assume now that a voltage change takes place on the input side of capacitor 'I and that this capacitor upon discharging reduces the voltage drop in the resistor E so that the bias is removed from grid 3 in tube I. This tube then becomes conductive and produces a voltage drop across resistor 8 such that capacitor 9 discharges through the space path dz in the rectifier tube I0. This condition has no effect upon capacitor II since the space path d1 now becomes nonconductive.

With current reversals applied to capacitor 1, it will be seen that successive, but diminishing, amounts of charge will be applied to capacitor II, thus building up a voltage thereon in step- Wise fashion somewhat as shown in Fig. 4.

As the charge increases on capacitor II, the normally negative bias on grid I4 with respect to the cathode I5 in tube I3 is reduced until tube I3 becomes conductive. A- triggering action takes place due to the'- interruption of current flow in tube I'I. A conductive state in tube I3 produces a voltage drop in resistor 23 which results in applying a relatively negative bias potential to the grid 2li in tube I'I. 'I'his bias eventually becomes suiliciently negative to cut oil 4 v conduction in tube I1. The voltage drop in cathode resistor I2 is then entirely attributable to the discharge in tube I3. The conductive state in tube I3, however, is such that there is suincient grid current to discharge capacitor II to ground potential. This discharge is quite sudden and permits subsequent application of incremental charges on capacitor II from ground potential as heretofore described. 'I'he number of such incremental charges which is required to produce conduction in tube I3 after it has been biased to cut oil.' is largely dependent upon the ratio between the capacitances of capacitors 9 and II and is also dependent upon the setting of the tap 22 on potentiometer 2i. 'I'he reason for the inuence ot the latter is explained as follows:

The see-saw interaction between tubes I3 and I 'I can readily be understood, since conduction in tube I3 produces a negative surge impulse through resistors 23 and 2| for application to the grid 20 in tube II, thereby cutting of! current fiow in this tube. The reverse action occurs upon an increase in the voltage drop in potentiometer 2I when a. cut-of! bias on grid I4 causes the voltage on anode I6 to rise. It is then that the bias on grid 2U permits current to flow in tube Il. Its cathode I3 has a tendency to develop a greater voltage drop in cathode resistor I2 so as to drive both cathodes I5 and I9 more positive. The resulting eiect is to increase the negative bias 01' the grid Il with respect to cathode I5, which accelerates the interruption of current iiow in tube I 3.

If the ratio between the capacitances of elements 9 and II is small, the increments or steps of charge on capacitor II are few in number. If the ratio is large, it requires a larger number of increments to charge capacitor II to full voltage. It is the number of these increments of charge which determines the count or integration of applied input pulses before the charge on capacitor II becomes eiective in rendering the tube I3 conductive. The count can be varied, however, by varying the time constant of the interaction between tubes I3 and I'I as by adjustment of the tap 22 on potentiometer 2I.

. A significant feature of the circuit arrangement of Fig. 1 may be appreciated when it is seen that there are no resonant circuits to be dealt with, so that it is of no importance. relatively speaking, what the periodicity or aperiodic nature of the input impulses may be. A definite number of such impulses is counted with each cycle of operation of the tube I3. Hence the output pulses which may be taken oil between the anode I5 and the cathode I5 is a definite sub-multiple of the number of impulses applied across the capacitor 1.

Referring now to Fig. 2, a. modification is shown with respect to that part of the circuit of Fig. 1 to the right of the dividing line a-a. Like parts in the two iigures are given like reference numbers.

The interaction between tubes I3 and I1 is somewhat diflerent from that which is explained above in reference to Fig. 1. In Fig. 2, the grid 2li in tube I'I is connected to a junction point between two resistors 21 and 23 of a voltage divider which corresponds with potentiometer 2| in Fig. 1. That is to say, resistors 21 and 28 interconnect the anode I6 of tube I3 and ground. It is, however, unnecessary to provide a, movable tap for' control of the bias on the grid 20 since provision is made by means of an adjustable potentiometer .25 for adjusting the cathode potential in tubes l close to or above I3 and` I1 with respect to ground. Variation of this cathode potential is due to variations in the potential drop across resistor 23 which in turn arises with changes in the conductive state of tube I3. A-triggering action is explained in more detail as follows:

Assuming first that the charge on capacitor II is so far reduced that a negative bias is applied to the grid I4 in tube I3. This tube is then nonconductive. The lack of anode current reduces the voltage drop in resistor 23 to a negligible value. The portion of potentiometer 25 which lies above the tap 26 is in shunt with the space path in tube I1. The position of tap 25 is adjusted to carry the cathodes I5 and I9 at a positve potential with respect to ground. The full voltage of the anode supply source extends through resistors 24a, 23, 21 and 23 to ground, thus impressing a relatively positive bias on grid 20.

Under the conditions set forth in the preceding paragraph, tube I1 is rendered conductive because the grid 29 has a bias potential which is the potential applied to cath ode I9.

Assume now that a charge has been built up cn capacitor II sufficient to render tube I3 conductive. The potential drop in resistor 23 renders the grid 28 negative with respect to the cathode I9, and tube I1 becomes non-conductive. The effect of this is to reduce the potential drop in that portion of potentiometer 25 which extends from the tap 26 to ground. The potential of the cathode I5then approaches that of ground potential, which thereby swings tube I3 abruptly into a saturated conductive state. This accelerates the discharge of capacitor II and the cycle of recharging by small increments is repeated.

Referring now to Fig. 3, I show therein a modification in which the principles explained in reference to Figs. 1 and 2 are applied along with a technique which permits the counting of incremental charges on the capacitor II to be differentiated in successive cycles. That is to say,

'if the input pulses applied acrosscapacitor 1 and amplified in the tube I are to be counted up to a number such Vas I1, this can be done by two stages in one of which eight incremental charges on the capacitor II are counted, and, subsequent to the discharge of capacitor II, nine incremental charges arecounted. The latter action will be such as to build up a ilnal voltage sufficient to be respondedv to by a cathode follower tube 29 which possesses a cathode resistor 36 across which a potential drop is produced when the tube 29 becomes conductive and this potential drop may be utilized in an output circuit for controlling any desired utilization device. '.By way of explaining the circuit arrangement of Fig. 3 in more detail, the following description is given:

The amplifier tube I is associated with a rectier tube I Il in substantially the same manner as is shown in Fig. 1. The capacitor I I also is connected in the same manner between one of the cathodes in tube I0 and ground. Connection is made between the same cathode in tube III and the grid I4 in tube I3 through one winding ofv a transformer 3l. The other winding of this transformer constitutes a feedback circuit between the anode I 6 and a potentiometer 32 which leads to a ground connection. The potentiometer 32 is in shunt with a by-pass capacitor 33.

6 diiIerent times in dependence upon the see-saw interaction betweentwo gaseous discharge tubes 34'and 35. Each of these gaseous tubes is constituted as a triode having a cathode 36a, 36h, an anode 31a, 31h, and a control grid 38a, 38h. The cathode 33a is connected to ground through a cathode resistor 39. The cathode 36h, however, is connected to a tap 40 on the potentiometer 32. The grids 38a and 38h both possess grid leak resistors 4I connected to ground. Control impulses for igniting the tubes 34 and i35 alternately are applied across capacitors 42vand 43 respectively. The anodes 31a and 31h are intercoupled by capacitor 44. A capacitor 45 is in shunt with a portion of the potentiometer 32' which lies between the tap 43 and ground. Anode potential is applied to the anodes 31a and 31h through resistors 41 and 43 respectively.

In the operation of the circuit arrangement of Fig. 3, the taps 4I! and 46 are. adjusted on the potentiometer 32 so that the desired count of incremental charges on the capacitor- II will be obtained covering the periods between successive discharges of this capacitor.

If, for example, the input pulses applied to the tube I and rectified in the tube I0 are to be effective in a series of iirst eight and then nine charges upon capacitor II, then the tube I3 will in the iirst case be held non-conductive while eight incremental charges are applied to capacitor II, and in a subsequent case, the tube I3 will be held non-conductive while nine incremental charges are impressed upon the capacitor II. In order to accomplish this result, the potential drop between tap 40 on the potentiometer 32 andground is varied so as to swing the cathode potential I5 between two values depending upon whether tube 35 is ionized or extinguished. The amount by which the potential of cathode I5 diifers from ground potential determines the ultimate charge on capacitor II before this charge is drawn off through the space path between the grid I4 and the cathode I5 in tube I3. Each time that tube I3 becomes biased to cut-off, a surge impulse of positive value is applied across capacitors 42 and 43 for igniting one of the tubes 34 or 35 which was at that instant non-conductive.

' The control pulse, however, has no effect upon the gaseous. tube which is already ignited. The ignition of one of these tubes lowers its anode potential suddenly and produces a surge im-V pulse across capacitor 44 so as to reduce the anode of the previously ignited tube to the exi tinction voltage.

Thus when tube 35 becomes ignited, the cathode 36h rises in potential and renders the cathode I5 in tube I3 more positive. When tube 35 is extinguished. then the cathode I5 is reduced to the lower of its two limiting potentials.

Fig. 4 illustrates the voltages which are applied incrementally across the capacitor II in successive trains. One train has seven incremental charges, and the other eight, by way of illustration. The tube 29 has circuit parameters such tha't it is rendered conductive only after a build-up of voltage on the capacitor II equal to eight elemental increments. As previously explained, the control of a conductive state in tube 29 may be used to derive the desired output pulses which count any desired number, includling a large prime number. This will be understood when it is seen that it requires the two flights of steps 8I9 to render the tubel 29 conlThe tube I3 is subject to different biases at 15 ductive- In 0151191' Words this tube beomes C011' ductive only once in seventeen applications oi the input pulses across capacitor 1.

It will be apparent that by suitable choice of the circuit parameters in the arrangement oi Fig. 3, any desired number of input pulses can be counted. This circuit arrangement has a wide range of applications in electronic flelds, particularly in television systems and in synchronization of different forms of apparatus.

My invention is not limited in its scope to the few illustrative embodiments hereinabove described and shown in the drawings. Modifications rnay readily be made by those skilled in the art.

I claim:

1. An electronic counting system comprising a coupling condenser and a storage condenser, a twin diode discharge device having one set of complementary electrodes in circuit between the two said condensers. the second set oi' complementary electrodes being disposed in a discharge path for said coupling condenser, means including an electron discharge tube having a cathode, an anode and at least one grid for intermittently discharging said storage condenser, said tube having means in circuit therewith for producing staggered conductive states therein whereby it is caused at intermittent times to respond to the build-up of a storage condenser charge having the integrated value oi one predetermined number of uni-directional pulses transferred from said coupling condenserto said storage condenser, and whereby said tube is caused at alternately intermittent times to respond to the build-up of a storage condenser charge having the integrated value of a different predetermined number of such uni-directional pulses.

2. A system in accordance with claim 1 and including a multivibrator circuit arrangement in said means for producing staggered conductive states therein, said arrangement being of the gaseous discharge tube type.

3. An electronic counting system having a single frequency-dividing stage, an input circuit for said stage characterized by the inclusion of a storage capacitor receptive of incremental charges which are derived from an energy pulse source, said capacitor being intermittently dischargeable through a path of electronic emission in said stage, a source of control bias potential for blocking the emission in said stage, and means for shifting the unblocking bias between two alternate values eective with each successive discharge of said capacitor, whereby rst one submultiple and then another submultiple of the energy pulses are derived.

4. A system according to/claim 3 in which a multivibrator circuit arrangement is included in said bias shifting means.

5. In an electronic counting system having a single frequency-dividing stage and a storage capacitor in theinput circuit of said stage, the method of counting two successive trains of energy pulses which are applied to said capacitor .capacitor chargeable by each of said pulses to a predetermined voltage, a second capacitor, a unilaterally conductive device interconnecting the two said capacitors and operative to transfer half-waves of pulse energy to the second capacitor, means including a second unilaterally conductive device in circuit with the ilrst said capacitor for reversing its charges, a trigger-acting electronic circuit of the multivibrator type having two space discharge systems which are rendered conductive at mutually exclusive times, one of said discharge systems being controlled by the build-up of a predetermined triggering potential in the second said capacitor, a discharge path for said second capacitor being produced by a conductive state in the same one of said discharge systems, means for so adjusting the parameters of said trigger-acting circuit that a predetermined number of said energy pulses. irrespective of their frequency, occurs between successive discharges of the second said capacitor, and input electrode biasing means applicable to one of two discharge systems in said trigger acting circuit whereby a predetermined count of pulses in certain intermittent trains is complemented by a different predetermined count of pulses in intervening trains.

HARMON B. DEAL.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,927,676 Bedford Sept. 19, 1933 2,284,101 Robins May 26, 1942 2,078,792 FitzGerald Apr. 27, 1937 2,110,015 FitzGerald Mar. 1, 1938 2,114,016 Dimond Apr. 12. 1938 2,113,011 White Apr. 5, 1938 2,185,363 White Jan. 2, 1940 2.354.930 Stratton Aug. l, 1944 2,363,810 Schrader et al. Nov. 28, 1944 2,250,202 Matusita July 22, 1941 2,221,452 Lewis Nov. 12,1940 2,258,943 Bedford Oct. 14,1941

FOREIGN PATENTS Number Country Date Great Britain May 26, 1932

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