US2549874A

US2549874A - Electronic relay circuit arrangement

Info

Publication number: US2549874A
Application number: US762375A
Authority: US
Inventors: Williams Frederic Calland
Original assignee: Individual
Current assignee: Individual
Priority date: 1943-06-25
Filing date: 1947-07-21
Publication date: 1951-04-24
Anticipated expiration: 1968-04-24
Also published as: FR958129A; GB582758A; CH268974A; NL75432C; BE478975A

Description

April 24, 1951 F Q W|| |AM5 2,549,874

ELECTRONIC RELAY CIRCUIT ARRANGEMENT Filed July 2l, 1947 3 Sheets-Sheet 1 AL HAAAAA AAAAMLMAAA" GZ/ -www-v GK@ R9 AAAAAAA *a FIGJ P2 gg l v C3 l T C' 'R4 I Eme TCA l y LL c. WILLIAMS April 24, 1951 F, c. WILLIAMS 2,549,874

ELECTRONTLC RELAY CIRCUIT ARRANGEMENT Filed July 2l, 1947 5 Sheets-Sheet 2 STAGE'.-

A zsvl l' I p l p 41V- 38V- B o' P2\ d l l i TmC F. C. WILLIAMS /m/emor April 24, 1951 F. c. WILLIAMS EEECTRONIC RELAY CIRCUIT ARRANGEMENT s sheets-sheet 3 Filed July 2l, 1947 OQO@ 4 .umg

'z'. c. names FIGS Attorney Patented pr. 24, 1951 ELECTRONIC RELAY CIRCUIT ARRANGEMENT Frederic Galland Williams, Timperley, England Application July 21, 1947, Serial No. 762,375 In Great Britain June 25, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires June 25, 1963 17 Claims.

This invention relates to electronic relay circuit arrangements of the kind in which an applied impulse causes the potentials of the electrodes of a multi-grid thermionic valve to pass through a predetermined cycle of changes and then to revert to their initial or stable condition. Such a valve is known as a relaxation relay.

The object of the invention is to provide a relaxation relay circuit arrangement which is reliably operable to introduce a variable time delay between an applied impulse and the operative response and which, among other applications, may be used as a frequency counter or as a frequency divider.

According to the invention a feed-back resistance is provided in the cathode circuit of the valve, the anode of the Valve is back-coupled to the grid nearest the cathode through a condenser and provision is made for controlling the duration of the waveforms developed by the electrodes of the valve in response to the applied impulse.

According to a feature of the invention, the feed-back resistance in the cathode circuit is of such a value that in operation the cathode potential follows substantially that of the control grid and the time interval between the application of the impulse and the reversion to the stable condition is determined by the difference between the anode and control grid voltages in the stable condition for given values of a fixed voltage to which the control grid tends to rise during the predetermined cycle of changes and of the time constant of a circuit which includes a condenser coupling the anode and the control grid, or by the Value of a fixed voltage to which the control grid tends to rise during the predetermined cycle of changes for given values of the difference between the anode and control grid voltages in the stable condition and of the time constant of the circuit including the feed-back condenser.

According to a further feature of the invention, the cathode potential is arranged to follow the control grid potential, the grid being connected to a fixed tapping on a potentiometer through a diode valve and to a fixed voltage through a resistance while the anode is back coupled to the control grid through a condenser.

In operation the applied impulse causes current to flow in the anode circuit causing an initial fall in the anode voltage and this is fed back to the control grid. This fall in anode voltage continues until the control grid is biassed almost to the cut-off value when the diode, which is conducting in the stable condition, ceases to pass current and the control grid potential tends to rise to the value of a xed voltage. During this rise of control grid voltage, the anode voltage continues to fall linearly at a rate which is ad- .justable and depends upon the value of the fixed voltage and the time constant of the circuit whichv includes the coupling condenser. When the anode voltage approaches the cathode voltage, which has been following the grid Voltage, the anode voltage ceases to fall and the control grid voltage rises rapidly towards the fixed voltage until the diode valve conducts and maintains the control grid potential at a steady value. The cathode potential also rises during this stage and eventually cuts off the anode current when the circuit has been returned to the stable condition.

It can be shown that the duration of the predetermined cycle of changes is dependent upon the difference between the anode and control grid voltages during the stable condition and upon the rate of fall of the anode voltage over the linear range. Further this rate of fall of anode voltage is dependent upon the fixed voltage to which the control grid tends to rise during the cycle and upon the time constant of the circuit comprising the condenser and resistance since this controls the rate of rise of control `grid voltage. The duration can therefore be varied by Varying any one of these factors but in the practical embodiments of the invention only two are varied, namely, the difference between the anode and control grid voltages and the value of the xed volta ge.

The difference between the anode and control grid voltages during the stable condition is varied by connecting the anode through a limiting diode valve to a variable tapping point on a potentiometer connected across the source of high tension voltage. Where the fixed voltage to which the control grid tends to rise is to be varied, the anode is connected to a fixed tapping point on the potentiometer and the control grid is connected to a variable tapping point on a second potentiometer which is also connected across the high tension supply.

Preferably the multi-grid thermionic Valve consists of a pentode, a negative bias relative to the cathode being normally applied to the suppressor grid to prevent fiow of anode current. Negative or positive impulses may be used to cause the initial fall of anode voltage, the negative impulses being applied to the cathode of either of the limiting diodes while the positive impulses are applied to the suppressor grid. The output 3 may be taken from the cathode or screen grid circuits of the pentode.

The invention will be better understood from the following description of alternative embodiments taken in conjunction with the accompanying drawings. In these drawings- Fig. 1 shows one embodiment.

Fig. 2 shows the relationship between an input voltage wave-form and the resulting. voltage wave-forms on the various electrodes of the pentode valve shown in Fig. l.

Fig. 3 and Figs. 5 and 6 all show alternative. arrangements embodying the invention While Fig. 4 is an explanatory diagram of part of the operation of the circuit.

Referring to Fig. l the cathode of a valveV V2! is connected to earth through a load resistance R-which serves to maintain the Voltage on the cathode at approximately the same value as that on the rst or control grid Gl. The anode of the valve is back-coupled through a condenser C2 to the control grid Gi which is also connected through resistances R1, R9 to the H. T. supply, and through the anode/cathode path of a limiter .diode V3 to a fixed tapping P2 on the shunt potentiometer P comprising resistances Rl, R2, R3 and R4. The condenser C2 and resistance R1 provide a desired time-constant factor; while the tapping P2 sets a fixed upper limit to the positive voltage which can be developed by the control grid Gl. The suppressor grid G3 is biassed from a Xed tapping Pl on the` shunt potentiometer P. The anode/cathode path of another diode VI is connected from the anode of the valve V2 to a variable tapping P3 on the shunt potentiometer. rThis tapping .determines the biassing potential which is initially applied to the anode, and provides an elective control over the shape and duration of the wave-forms generated by the valve.

In the normal or quiescent condition of the valve V2 a bias potential, negative with respect to the cathode, is applied to the suppressor gridv G3 which blocks the valve by diverting the electron stream away from the anode to the screen grid G2 to `which a positive biassing voltageis applied through resistances Ri, RI E. The Voltages on the anode and control grid GI are fixed by the limiter .diodes VI, V3 respectively, whilst the cathode voltage is held at approximately the same Voltage as that of the grid Gl by the cathode load resista-nce R5. The two diodes VI, V3 may be housed in the same glass or metal container.

In the arrangement shown, the valve V2 is rendered more conductive or is triggered by a negative impulse represented at p in' wave-form A Fig. 2 applied through a condenser C3 to the cathode of the diode V3. The wave-form B shown in full lines in Fig. 2 represents the cathode potential and the dotted line wave-form that of the control grid Gl. The drop in the potential of the grid Gl resulting from the impulse p and represented by the steep portion pl in the wave form B, is communicated in known manner through the resistance R7; to the cathode of the valve V2 and serves to overcome the initial blocking eiect of the suppressor grid G3 the potential level of which is represented by the point 12E-in wave form B. The anode accordingly takes current, and its Voltage, as represented by the wave form C in Fig. 2, begins to fall along a. path which is momentarily steep, as shown at p3. This fall of voltage is fed back to the grid through condenser C2 and the grid and anode voltages 4 fall together until the grid voltage is such that anode current is almost cut off. The diode V3 ceases to conduct as the grid goes negative and as no grid current is flowing the grid voltage tends to rise towards the level of the high tension supply due to the connection of R'I. The steadily rising grid voltage causes the anode Voltage to fall further and this fall is in turn fed back through condenser C2 to oppose the original rise of grid voltage, with the result that the anode voltage falls linearly along a lower gradient as shown at p41 The fact that the anode voltage falls linearly can be seen by considering Fig. 4.

From this drawing C2 VaVz :q

VHT-V.=i.R7

Hence;

all/ dVg l d qlm; l

di (u +02 di di c'aRWHT V) Now Vg is small compared with Va and VHT so. that approximately d n- VHT dt 02.R7

Thus Va falls linearly` and the rate of fall depends on VHT and the time constant of the circuit C2, R1. If the high tension voltage is taken from a tapping on a potentiometer (Fig. 3 of the drawings) and has a value VL, then The linear fall of anode voltage continues until the cathode voltage which has been following the grid, and the falling anode voltage approach. At this point the rising grid voltage tends to increase the space current of the valve and the falling anode voltage decreases the anode current with the result that the anode voltage remains substantially constant. Due to the cessation of the negative voltage fed back from anode to grid, thel grid then rises rapidly towards the level of the high-tension supply. The cathode, following the rising grid Voltage, then reaches the level p2 at which the suppressor grid again diverts the electron stream from the-anode to the screen grid. With the anode current cut off both anode and grid voltages then rise rapidly towards the H. T. level, the potential of both plates o condenser C2' changing together. Atv the predetermined level, the diode V3 conducts and the grid is then held at its intial biassing potential for the quiescent condition. The anode voltage then begins to rise towards the level of the high-tension supply, following an exponential curve p5 which is due to the presence of the condenser C2. The rise continues until the diode Vl comes into action and holds the anode at its initial potential' at the point p6. Meanwhile the potentials on the cathode and on the first and second grids Gi and G2 have also reached their initial values, and the` circuit is reset to receive the next triggering impulse. Theresulting output represented by wave form D is taken from a terminal O connected with the screen grid.G2.

A modification of the arrangement described above is shown in Fig. 3. The high potential end of the resistance R. is taken to a variable tapping Pill on a shunt potentiometer comprising resistances R l 2, RI 3 instead of being connected directly to the high tension line. The cathode of the diode Vl is connected to a xed point on the potentiometer P. As explained previously, the

linear rate of fall of the anode voltage ls now directly proportional to the voltage at P4 and inversely proportional to the time constant of the circuit C2, R1. Y

The duration d of the steady voltage on the screen grid is approximately equal to the delay T and is given by d"change in Va during stage 2 dVa/dt stage 2 being shown in Fig. 2. Since Vg and Vc do not alter by more than one or two volts during stage 2 and Vfl-Vg changes only by a very small amount in stage I, this may be written change in Va--Vg during sta8e2 dVa/dt CZ change in (V)-(Vg)0 during stage 2 dVu/dt l l But the final value of (Vwo-(Vwo is approximately zero sothat (,:Wao- (Voozuvat-Woolcam dVa/dt VHT where VHT is the high tension voltage or in the case where the high tension voltage is provided by a tapping on a potentiometerV Where V1. is the voltage at the tapping point. Thus a variable delay may be obtained by varying the initial anode voltage (i. e. varying P3) or by varying the voltage to which the control grid of V2 tends to rise (i. e. varying P4). It may also be varied by varying the time constant of the circuit C2.R1.

A further modification of the circuit shown in Figs. 1 and 2 is illustrated in Fig. 5. In this case a negative triggering impulse is applied to the anode of the valve V2 through a condenser C3 and the cathode/anode path of the diode Vl, and the output is taken either from the screen grid or the cathode of the valve V2 according as to whether a positive or negative-going waveform is required. A resistance R8 is inserted between the tapping point P3 and the cathode of VI. In operation the initial impulse produces a drop in anode voltage, which is passed through the condenser C2 to the control grid. The resulting waveforms developed by the various electrodes then follow the same cycle as that already described.

In a further modification of the circuit, shown in Fig. 6 a positive triggering impulse is applied through a condenser C3 to the suppressor grid of V2 and the output is taken from the cathode or from the screen grid. The suppressor grid is negative with respect to the cathode during the stable condition and the positive impulse renders it positive with respect thereto, thereby causing the anode to take current to initiate the same cycle of operations as before.

In the operation of the circuits described above,

a waveform of selected duration or width is obtained from the valve V2. By shaping or squaring this output Wave and passing it in known manner through a differentiating circuit of suitable time constant, an operative impulse can be derived after a predetermined delay of between say a few microseconds and a few milliseconds from the application of the initial triggering impulse to the relay.

When the circuits are used as frequency dividers, adjustments are made so that the total delay T is n times the frequency t of the applied impulses. The circuit is triggered on the anode of V2 and then responds only to every nth applied impulse and remains insensitive to the effect of intermediate impulses so that the output frequency is that of the input frequency divided by n.

Although the high tension supply is preferably maintained constant, the operation of the circuit is independent of casual fluctuations, provided these affect all the electrodes proportionately.

I claim:

1. An electronic relay system comprising in combination, an electron discharge device having a cathode and also having the following elements removed from the cathode in the order named, a control grid, a screen grid, a further grid, and an anode; a source of direct current power having positive and negative terminals; a resistance connected between said cathode and said negative terminal; means connecting the screen grid to said positive terminal; means for diverting the cathode current from the anode to the screen grid during the quiescent condition of the system comprising bias means of less potential than is developed in said resistance during the quiescent condition; said bias means having its positive side connected to said further grid and its negative side connected to said negative terminal; a resistor connecting said anode to said positive terminal; a timing circuit including a condenser connected between said anode and said control grid, and a resistor between the control' grid and said positive terminal; and means including an input circuit connected to one of said elements and responsive to an input impulse to effect current ow from the cathode to the anode.

2. The relay system of claim 1 including in addition limiters respectively connected to different percentages of the direct current source to respectively limit the positive potentials on said anode and said control grid to positive values not in excess of those representing quiescent condition.

3. An electronic relay circuit comprising in combination, a thermionic valve having at least the following electrodes disposed in the order named, a cathode, a control grid, a screen grid, and an anode; a connection including a condenser between said control grid and said anode; a direct current voltage source having positive and negative poles; .a direct current path including a resistance between said cathode and r said negative pole; a direct current path including a resistance between said control grid and the positive terminal of said source; a connection between the screen grid and said positive pole; means for applying a bias voltage to an electrode of said valve to affect the anode current in said valve; said last-named means including means for varying the division of cathode current between the anode and screen grid in accordance with the current variations to one of the electrodes of the valve; a further grid locatedibetween the anode and. screen grid and ing disposed in the order named, acathode, a.

control'grid, avv screen grid, a suppressor grid,.and an anode; a source of direct currentvoltage.; a resistance connecting1 said; cathode to the negative terminalV of .saidtsource, a .resistance connectingj said control grid tothe positive terminal. of.

said source; a resistance connecting said. screen grid to: the positive terminal. of sa-id source; a. potentiometer across said source of` direct. current voltage., a. connection including a. unilaterally conducting device. between said control grid and a tap on saidpotentiometer, a connection between said further Vgrid and a tap on said potentiometer'of lower positive voltage than that to which. said control grid is connected;` a connection including a unilaterally conducting device between said anode and a tapping on said potentiometer or' higher voltage. than that to which said control grid isconnected; and a connection including a. condenser between said control grid and said anode.

5.V An electronic. relay circuit comprising in combination, athermionic valve having a cathode, an anode, and a. control grid, a screen grid and at least. one further grid in that order between said cathode and said anode, a source of space. current. potentials for said valve, a source of` biasing potential for said valve, a load resistance connected between said cathode of said Valve and a negative terminal of said spacecur.- rent source, circuit means including a high resistance connecting said control grid to a point of high positive potential on said space current source, and anode circuit including a high resistance connectingA said anode to a point of high positive potential on said space current source, a coupling circuit including a series condenser connected between said anode circuit and said control. grid, a screen supply circuit including a series-connected resistance connected between said screen grid and a point of high positive potential on said space current source, circuit means. connecting said further grid to a point on said source of biasing` potential such that, in the normal quiescent condition of the circuit said suppressor grid is biased to block anodeY current flow' through thev valve and to divert the space current to nowthrough said screen supply circuit, and circuit means for injecting an input triggering pulse voltage to at least one of said anode, said control grid or said further grid of said valve of such polarity as will produce a removal-:of thebl'ocking'eiect of said suppressor grid biasY potential.

6'. The electronic relay circuit of claim 5, which comprises circuit means including a unilaterally conductive device connectingsaid anode of said valve toa point of chosen positive potential on said biasingpotential source, whereby the voltage of said anode-is preventedfrom rising more positively than said chosen potential value.

7. They electronic relay circuit of claim 5, which comprises circuit means including a unilaterally conductive' device connecting said control grid of said valve to a point of chosen positive potential on said biasing potential source whereby the voltage' of said control grid isA prevented from rising more positively tha-n said chosen potential value.

8. The electronic relay circuit of claim' 5, which includes an. outputL terminal directlyfconnectedtosaidV screen-grid of..said;valve.l

9; rEhe electronic rela-y circuit ofclaim 5,. inE which said input triggering circuit meansfcom.- prises an input terminal. connected-.by way of a unilaterallyconductivedevicefto-the anode of.; saidy Valve.

10. The electronic relay circuit of claim 5, in which said.Y inputi triggering circuit means comprises an input terminal connected by way of a unilaterally1 conductive device: to: the controle grid o saidvalve..A

11....The. electronic; relayf' circuit of claim 5 in which said. input. triggering: circuit means-1 comprises an input terminal connected by way of a series condenser toY theV suppressor grid of said valve.

12 The` electronicy relaycircuit of' claim? 5,. ini which said circuit means byf which saidL controli gridi's connected to af-point' of= high positive po-- tential on said space currentl source includes a potentiometer network connected across.. saidv source and having its adjustable tapping connected through said-high resistanceto said' con-- trol-grid.

13. An electronic relayf circuit arrangement comprising-'- combinati'on, a thermionicvalve'. having at least a cathode and an-anod'ef-with a control grid,.af screen grid` and a suppressor grid disposed therebetween inthat order, a iirst terminal for connection of the negative terminal of a source offV space current for4A the va-lvej aresistance connected between said/'Y cathode of said valve andiV said rst. terminal, al second` terminal for connectionzto a point'of high positive potential of said source of. space current,. aY load resistance connected l` et`ween said; anode andv said second terminal', a charging resistance l connected between the controllgridof said valveand said second terminal, acondenser connected between said control-grid and said` anode of said valve, circuit means including, a load resistance connectedv between said screen-grid of`saidvalveand`saidlsecond terminal, apotentiometer network connected in shunt acrossfsaidY rst and. second terminals, ci-rcuitmeans includingr` a first series diode comprising an. anode. connected4 to. saidA control' grid and a cathode connected to a iirst tapping point on said potentiometer networln, further circuit means/including afurther` series diode. comprising an anode connectedto said. anode; of.` said valve, andA a` cathode. connected-to a second tap.- pingl point., on said` potentiometer network. which is appreciablyy more positive thany said rst.. tapping-point, a. connection between said.y suppressor grid ofA said valve and.v a tapping point. on said potentiometer. network. whichis more negative than said iirst'tapping point, and an output. terminal connectedto said screen-gridor saidvalve.

14. An electronic-systemcomprisingincombinationan: electron dischargedevicehaving acathode and also having the. following elements. removed from the cathode inthe. order nameda. control grid, a second grid, a further grid, and an anode; a` source of direct current power. having positive and negative .terminals a `resistor Yconnecting said cathodeand said-*negative terminal and constitut ing. the. only` means electrically connecting said cathode to.:A said; negative terminal; means con.- necting, theisecond. grid to said` positivey terminal; bias." meansfor theT further grid.. and` placing. a potential-thereon of. such value that the further gridfis. negativemvith respect'to` the cathode when the system is quiescenta resistor connecting-.the anode. to: said. positive terminal; a. timing circuit including a condenser connected between said anode and said control grid, and a resistor connected between the control grid and said positive terminal; and input means responsive to impulses including means for modifying the potential of one of said elements to a sufficient extent to effect current flow from said cathode to said anode.

15. An electronic system comprising in combination, an electron discharge device having a cathode and also having the following elements removed from the cathode in the order named, a control grid, a second grid, a third grid, and an anode; a source of direct current power having positive and negative terminals; a resistor connected between said cathode and said negative terminal and constituting the sole element connected between said cathode and said negative terminal; means connecting said anode to the positive terminal of said source; a resistor having a high value of resistance connecting said control grid to the positive terminal of said source; a coupling condenser connected between said anode and said control grid; a source of bias connected to said third grid to render the latter negative relative to the cathode during quiescent condition of the system; and means responsive to an input impulse to modify the relative potentials on one of the elements of said device to thereby develop current ow from said cathode to said anode.

16. An electronic system comprising in combination, an electron discharge device having the following elements in the order named, a cathode, a control grid, a second grid, a third grid, and an anode; a direct current power supply having positive and negative terminals; current conducting means that is primarily resistance connected between said cathode and said negative terminal and constituting the only means for passing current from the cathode to the negative terminal; rst, second and third resistors each respectively connected at one end to the control grid, the second grid, and the anode and all connected at their other ends to said positive terminal; a timing cond denser connected between said anode and said control grid; biasing means that places a Xed bias potential relative the negative terminal on the third grid which potential is of such value that the third grid is negative relative the cathode When the system is quiescent and positive relative to the cathode when maximum current is llowing through said current conducting means; and input means responsive to an impulse to modifying the potential on one of the elements of said device and thereby increase the anode current thereof.

1'7. An electronic system comprising in combination; an electron discharge device having the following elements in the order named, a cathode, a control grid, a second grid, a further grid, and an anode; a direct current power supply having positive and negative terminals; a resistor connecting said cathode to the negative terminal; a second resistor connecting said anode to the positive terminal; a feedback condenser connected between the anode and said control grid; means connecting the second grid to the positive terminal; biasing means for placing a xed bias on the further grid which is negative relative to the cathode during quiescent conditions of the system; and means responsive to an input pulse to modify the potential on one of the elements of said device and thereby start flow of anode current.

FREDERIC CALLAND WILLIAMS.

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

UNITED STATES PATENTS