US2568918A - Reset circuit for electronic counters - Google Patents

Description

a fhg 1. E. GRosDoFF RESET CIRCUIT FOR ELECTRONIC COUNTERS Filed Feb. 25, 195o Sept. 25, 1951 (l/NTE WPI/r Y Patented- Sept. 25, 1951 muri-:DpY STATES PATENT OFFICE vRESET CIRCUIT FOR ELECTRONIC COUNTERS of Delaware Application February 25, 1950, Serial No. 146,354

4 Claims. (Cl. Z50-27) The present invention relates toy electronic counting systems and. more particularly is an improved resetting system for electronic counter systems.

Electronic counting systems in general, use as abasis a chain or cascade of trigger circuits each of which is capable of .assuming either of two conditions of stability. `The basic trigger circuit with which the present invention is illustrated as being utilized is the trigger circuit of the general type described in Theory and Application of Vacuum Tubes by Herbert J. Reich, published in 1944. In one of its simplest forms, this trigger circuit includes two triodes in which the grid of the first triode is coupled to theanode of the Second triode through anetwork comprising a parallel connected resistor and capacitor, and the grid of the second triode is similarly coupled to the anodeof the first triode through a similar coupling network. The cathodes of both triodes are grounded. f Grid and anode potentials areapplied to the respective electrodesthrough separate resistors. Y

In operation, if a negative Vvoltageis applied to the grid of the rst triode, the anode current of the triode will be reduced and the anode potential will become' more positive. vDueto. the connection through the coupling resistor, the grid potential of the second triode will become more positive, causing an increase in the anode currentof the second triode, with a resultant decrease in the second triode anode potential. This decrease in anode potential wi11,in turn, cause the grid potential of the rst triode to .become more negative. This action will continue until the anode current of the first triode is cut off. The rst triode will remain cut off, and the second triode will remain conducting, until a negative potential is applied to the grid of the second triode. The tubes operating conditions are thereby reversed and the first l" 'generates a pulse which is appliedto -a third trigger circuit to cause it .to transfer conduction. As many trigger circuits as are required forobtaining a desired count may be used. By the use of feedv,back between trigger circuits, a `counter may complete a cycle of counting with fewer applied pulses than are required without feedback.

Regardless of the feedback connections between trigger circuits, all counter circuits, at the ,beginning of a count, usually have some -desired ""L'starting position with conduction in one `of the triodes of each trigger circuit. `Toattain this starting position at the termination of a count,V

a resetting circuit is usuallyprovided. This con- .sists of a reset pulse source whichis connected to ""a grid of one of the triodes in.y each of the trigger circuit usually generates pulses .which tend, to

drive the following trigger circuit and sometimes "-"do. This reset and settling down period, or total reset time, `seriously aiects thespeedof these types of counters. and .thus 4their, Aapplication in..

situations requiring. continuous rapid successions 4of counts is prevented or requires an alternate.

counter which can be switched on to allow time triodebecomes conducting andthe anode current i.

of the second triode is cut oi.

For the purposes of counting, a pulse is usually applied to the rst trigger circuit in the chain to transfer conduction from one tube to the other. The next pulse, applied to the rst trigger circuit,

transfers conduction back to the rst tube andA atv the same time a pulse is generated by the first trigger circuit which is applied ,toA the second trigger circuit to cause a transfer in conductionv to the second trigger circuit to restore it to its starting condition. This latter actionv in turn forreset. v,

It is therefore an object of the present invention to provide an improved reset circuit which npermits a faster reset of an .electronic counter' than was possibleheretofore. y

It is a further object of the present invention to provide an improved reset circuit which dissipates pulses generated bythe resettingaction.V

It is still another object ofthe present. invention to provide a new and improved reset Y.circuit for an electronic counter.

These and furtherl objects. are achieved, in .ac-

cordance with,thepresentinventiom by coupling a diode or, rectier from ,the grid of the tube .in

each trigger circuit which it is desired to reset to the cathode of a cathode follower tube. vA bias i s n applied to the diodes through the .cathode load.

impedance so, that'there is no interference with the operation of the counter during a counting interval. Whenreset isdesired, a reset pulse is apv.

plied to the cathode follower andthrough each nection with the accompanying drawing, which represents a circuit diagram of a preferred em-V bodiment of the invention.

Three stages of a well-known '.binarytypeofg;

counter are shown, each stage consisting otra..V

trigger circuit which is connected to apply a pulse to the subsequent trigger circuitiafter. it hashad two pulses applied to its input.'

The counter is arranged to be driven by negative pulses. counter, is the one wherein current conductionA is in the right hand tube of.v each trigger circuit, as shown by the arrows.

' A negative inputl pulse is applied through a condenser vIIJ to the cathodesjllofthedouble diode I2."V Each of the anodes 'I6 of the'double'dio'de I2 are connected to agri'd 24,30 of "each of the triodes I8," ofthe rtriggercircuitrcomprising the first counter stagefgAgrid1eak`resistor I3 'couples the diode cathodes to ground. The triodes I8, 28 have individual load'iresi's'tors 34, 36 connecting each of theiranode's'26, 32A to a source of 'anode potential. Theleft triodeanode 28 is connected to the right triode grid 30 through a parallel connected'resstor 38 and '40. The right triode anode 32 is also coupledlto the vleft triode grid 24 'by a parallel connected 'resistor 42 -conde'nser' 44 "combination. Although' thetrgger circuits are shown as' having triodes,'. multi'grid electron discharge tubes may be substitutedltherefre in a manner which is well known to thbseskilled in the art. Each of 'the grids'.24,'3 0`of th'etrides I8, 2B are connected to a source of negative Ybias through a separate resistor 461148,Y The trigger circuit components and th'e applied Abias have their values selected so that the trigger circuit has two stable states. One withiconducti'o'n in the right triode 20 and the other with',.conduction,V in the left triode I8.

The first negative input-pulse is applied through the double diode IZto. .both 'grids 24, 30 'of the first trigger circuit tubes. This has no effect on the left triode IIl'whichfis already.,non-conduct ing. but the negative pulse causes the righttriode 20 to go to cut-oil'. This causes` a positive pulse toV be generatedat the rightftriodeanode 32 which is applied to the leftv triode ,grid 24 causing the left triode I8 to becomecconductive...

The next negative .pulse appliedftn the first trigger circuit throughlthe double diode I 2 causes a reversal of conduction from theleft triedo I8 to the righttriode 20. 'Inbecoming conductive the right triodegenerates. a negative pulse at its anode 32. Besides this pulse being; applied to the.

tion as the first triggerfcircuit. i Each trigger cir-V The zero, or reset conditionof thev Y cuit goes from its initial orzerostate to-.itssecond the succeeding trigger circuit in returning from its second stable state back to its zero state. Therefore, one output pulse is received from the third trigger circuit in response to eight pulses being applied to the rst trigger circuit.

If, at any time during?. count, it is desired to resetthe countento itsrinitial orezero vcondition with conduction in all the right triodes, a positive pulse, also known as a reset pulse, is applied to the right triode grids 30, 30a, 30h of the counter..:.'1'l1`is.. fhas the effect of causing all the right triodes 20, 20a, 20h being driven from a nonconducting V,to a conducting condition, to generate negativepulses.;V Tli'ese negative pulses are applied throughtheycoupling condensers and double diodes to the subsequent trigger circuit grids andtendI to1oppose the effects of the reset pulse. Thiscauses the counter to be jittery and some time must be permitted for it to settle down before being used again.

These difficulties may be eliminated by coupling to the counter a reset 'circuit which is a preferred embodiment ofthe present'invention. This includes a diode or rectifier 50, 50a, 50h for each triode that is'being; reset. A cathode follower tube 56 is also provided having a load impedance` or resistance 58 connected to itscathode 60." Each' diode cathode 52,' 52a, 52b'isfconnected to the grid lof the triode being reset.' In' thisginstance, these are the right grids 30, 30m-3M);4 Each diode anode 54, 54a, V54h is connected 'tothe cathode 60of the cathode follower tube. Anegative bias is applied i to the cathode follower grid62and to the anodes 54; 54a,'54b of thediodes 50;,'50a, 50bthrough the load impedance 5B of the cathodelfollower tube 56. This serves thepurpose of keeping the anodes4 of therdiodes 50, 5021,1150b`negative with respect to their cathodes even when negative pulses are applied to the grids to whichth'e cathodes are connected. By this expedientthe reset circuit. does.

not interfere withtheloperation, of the counter wh'ile counting. Effectively a high-impedance is presented tothe grids bythebiased diodes.

When it is ,desiredto reset .thecounten a fposif tive or reset pulse isapplied to. the grid B2 of the cathode follower. The lsignaljon .the cathode 50 follows the grid signal v.and.-thus,a positive pulse.V

is applied throughthe-ldiodes,501 `5021, 50h vto Vthe source present f-a.low impedance pathmto such negative pulses duringthe time of..app,lication ofv the reset pulse. 'Thenegativepulseswhich could` cause jitter are thereby. dissipated4 without affecting thetrigger circuit stability., The value of the cathode load resistoriofthe.cathode fol-` lower 56 is selected .gto .be lowwhen.compared with the value of each.of.. the grid. resistors I3.' I 3a, I 3b connecting, the gridsto ground or a vpoint of fixed potentiahorto the.resistor,4646a, 4Gb' through which negative .biasfzis applied to thew grids. The reset period -is thereby considerably shortened to be the. periodof. the duration of the reset pulse and the-.counter islavailable for a count immediatelyafter `the..termination.ofthe reset, pulse. Thus, the .biased diodes` maybe considered as,` unilateral ,impedancespresenting.

a high impedance. during.,theLcounting` interval, and. a low impedanceAV during..the; reset .pulse in, terval. Y

From the foregoing description, it will be readily apparent that an improved reset circuit has been described which provides faster reset time than was heretofore possible. Although a single embodiment of the present invention has been shown and described, it should be readily apparent that many changes may be made in the particular embodiment herein disclosed, and that many other embodiments are possible, all Within the spirit and scope of the invention. It will also be appreciated, by those skilled in the art, that the embodiment of the invention herein shown and described may be used with other types of l electronic counters than binary counters.

It is therefore desired that the foregoing description shall be taken as illustrative and not as limiting.

What is claimed is:

1. A circuit for resetting a chain of trigger circuits of the type wherein each trigger circuit has two stable conditions, one of which is a starting condition, an electron discharge tube having a grid electrode to which a voltage pulse is applied to reset said trigger circuit to its starting condition, and an impedance for coupling said grid electrode to a point of fixed potential, said reset circuit comprising an impedance the value of which is low when compared with the value of said grid coupling impedance, a plurality of unilateral yimpedances, each of said unilateral impedances being coupled between the grid of the tube in each of said trigger circuits to: which it is desired to apply a reset pulse and said low value impedance, means to apply reset pulses to said low value impedance, and means to apply a bias to said unilateral impedances through said low value impedance to have said unilateral impedances and said low value impedance appear to said grids to have an impedance value which is high when compared to said grid coupling impedance and an impedance value which is low during reset.

2. A circuit for resetting a chain of trigger circuits of the type wherein each trigger circuit has two stable conditions one of which is a starting condition and each trigger circuit includes an electron discharge tube having a grid electrode to which a voltage pulse is applied to reset said trigger circuit to its starting condition and an impedance for coupling said grid electrode to a point of fixed potential, said reset circuit comprising an impedance the value of which is low when compared with the value of said grid coupling impedance, a plurality of rectiers, each of said rectiers being connected between the grid of a tube in each of said pair of tubes to ywhich it is desired to apply a reset pulse and said low value impedance, means to apply reset `pulses to said low value impedance, and means to apply a bias to said rectiers to maintain said rectifier-s non-conductive except during reset.

3. A circuit for resetting a chain of trigger circuits of the type wherein each trigger circuit has two stable conditions one of which is a starting condition, and an electron discharge tube having a grid electrode to which a voltage pulse is applied to reset said trigger circuit to its starting condition, said reset circuit comprising a cathode follower tube upon which reset pulses are impressed, a plurality of rectiers, each of said rectiers being connected between the grid of the tube in each of said pair of tubes to which it is desired to apply a reset pulse and the output of said cathode follower, and means to apply a bias to said cathode follower to maintain said rectiers non-conductive except during reset.

4. A circuit for resetting a chain of trigger circuits of the type wherein each trigger circuit has two stable conditions, one of which is a starting condition, and an electron. discharge tube having a grid electrode to which a Voltage pulse is applied to reset said trigger circuit to its starting condition, said reset circuit comprising a cathode follower tube having grid, cathode and anode electrodes, a load impedance, connectedtc said cathode follower cathode, a plurality of diodes each having an anode and a cathode, said diodes anodes being connected to said cathode follower cathode, each of said diodes cathodes being connected to a grid of the one oi each pair of tubes to which it is-desired to apply a reset pulse, and means to apply a bias to said cathode follower cathode to maintain said diodes anodes at a lower potential level than said diodes cathodes, except during reset.

IGOR. E. GROSDOFF.

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

VUNITED STATES PATENTS Number Name Date 2,403,918 Grosdoff July 16, 1946 2,493,058 Bliss Jan. 3, 1950 2,519,184 Grosdoif Aug. 15, A1950

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