US2203468A - Regulator for time delay circuits - Google Patents

Description

June 4, 1940. H. B. MARTIN 2,203,468

'REGULATOR FOR TIME DELAY CIRCUITS Filed Feb. 12, 1938 Fi .1 L

INPUTSIGNAL lvlllllllll D. C. SOURCE 7 VAR/ABLE BETWEEN 1 1'20 VOLTS MAX/1ND .90 VOLTS M/N.

(l/BRENT LEVEL AT WHICH RELAY l g. 2 3 o smrss PLATE CURRENT IN TUBE .5

3 ms POTENTIAL g APPLIED 7'0 GRID 7 L g Q I E 2 1 Q m: 3 I 2 4 8R mm /N g 1 OPERATION g 0F REL/1Y3 r: I A 4 c B L|,

BIAS CHANGES 0N GRID 7DUE T0 OPERATION OF RELAY 16 A CHANGE WHEN SOURCE DELIVERS 90 was B: CHANGE WHEN sou/ace DELll/ERS 105 VOLTS ,NVENTOR c= CHANGE WHEN SOURCE DELIVER5120 VOLTS HE CHEL MART/N ATTORNEY.

Patented June 4, 1940 UNITED STATES REGULATOR FOR T'IME DELAY CIRCUITS Herschel B. Martin, Brooklyn, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application February 12, 1938, Serial No. 190,233

7 Claims.

This invention relates to voltage regulator devices and, more particularly, to apparatus which would find general utility in certain types of radio apparatus.

I have found, for example, that in the operation of automatic call selectors such as used on ship-board for giving a signal in response to a distress call that it was necessary to provide a certain measure of voltage regulation particularly in order to control the operation of certain timing circuits within specified tolerances. My invention is, therefore, particularly adapted to uses of that character although more general applications may well be found for the invention by those skilled in the art.

It is an object of my invention to provide a voltage regulator suitable for use in such cases as would ordinarily prevail on ship-board for the operation of a radio receiving circuit and a call selector, where the power supply unit is subject to considerable voltage variations even greater than the tolerable variations in plate voltages to be supplied to the radio apparatus and voltages for operating timing circuits.

It is a further object of my invention to provide means for compensating the supply voltage as used in a time delay circuit so that such time delay circuit shall be held within workable tolerances of operation.

In carrying out my invention use is preferably made of a voltage regulator discharge tube in combination with a potentiometer so arranged that a needed grid biasing voltage supplied to another discharge tube shall be duly compensated 36' with respect to variations in the plate supply voltage applied to this last named tube.

My invention will now be described in more detail, reference being made to the accompanying drawing in which Figure 1 shows a circuit diagram of a preferred embodiment and Figure 2 is a graphic chart showing the operating characteristics of my preferred circuit.

Referring, first, to Figure 1, I show therein a conventional direct current source I which is indicated as being supplied by alternating current from any convenient generator connected to the input terminals 2. For purposes of illustration, the output from the D. C. power supply unit I may be considered as subject to variations within the limits 90 and 120 volts, the normal voltage being regarded as 105 volts. This power supply unit is, therefore, one which could ordinarily be obtained on ship-board where the generators are subject to considerable voltage variation due to the fluctuating load which they carry. The

positive terminal of the source I is shown connected through a relay 3 to the anode 4 of the electron discharge tube 5 which may, if desired, be of the pentode type. Such a tube ordinarily contains a cathode 6, a control grid 1, a screen grid 8 and a suppressor grid 9. As shown in the drawing, the screen grid 8 may be connected at a suitable point along a potentiometer section I0, which is connected between the positive terminal of the source I and the lead to the cathode 6. Another potentiometer section II forms a connection between the cathode 6 and the negative terminal of the source I. This negative terminal is also connected through a time delay circuit to the control grid 1 of the tube 5. The time delay circuit comprises a resistor l2 and a capacitor l3. This circuit is normally shorted out by a relay armature I4 resting against its back contact IS. The relay l6 will be understood to be included in a signal receiving circuit of any suitable type.

The components of the biasing voltage regulator section as shown in Figure 1 include a discharge tube I'! which may also be of the pentode type. This tube has a biasing circuit for its control grid l8 arranged through a' potentiometer consisting of two sections, I9 and 20. Section I9 is in circuit with an auxiliary D. C. source 2!, the positive terminal of which connects with the control grid Hi. The tap 22 connects the n ative terminal of source 2| to a point interme ate between the potentiometer sections l9 and 20. The position of this tap may be adjusted so as to provide a suitable normal operating bias on the grid 18 in opposition to the normal voltage drop across the potentiometer section 19 in relation to the normal output voltage of the source I.

In the operation of my invention it will be seen that as voltage variations occur in the direct current output from the source I more or less current will fiow through the regulator tube 11. This will cause fluctuations in the voltage drop across the potentiometer sections [9 and 2|] as well as fluctuations in the potential drop across the potentiometer sections II] and H.

' Under the conditions herein illustrated by Figure 1 it is to be understood that perfect regulation of the control grid voltage supply between the cathode 6 and the grid 1 of the tube 5 is not required. It is only required that this grid bias potential may be maintained within certain tolerances such that the timing circuit consisting of resistor l2 and capacitor [3 shall be rendered operative within comparatively restricted limits. It is the time constant of the timing circuit which must be held within close tolerances.

The biasing voltage regulator circuit is, therefore, adapted to supply a positive biasing potential as measured across the potentiometer sections I9 and 20 whenever relay I6 is operative for opening the circuit between its armature I4 and back contact I5 and for closing a charging circuit through a resistor 23, front contact 24 and armature I to the connection between said timing circuit and the grid 1.

In practicing the invention under the conditions herein contemplated it is the purpose of the timing circuit I 2 -I 3 to delay the operation of relay 3 for a predetermined time interval following the operation of relay I5. This time delay action is brought about by adjusting the value of the resistor 23 in relation to the capacitance of the condenser I3 and the ohmic value of the resistor I2. Thus, the biasing potential applied to the grid I is made to rise gradually from a point considerably below to and above the cutoff point. Before the condenser I3 becomes fully charged, however, the tube 5 is rendered sufficiently conductive so that the relay '3 operates. Since it is the purpose of the voltage regulator tube H to provide only partial compensation of the D. 0. supply voltage, it will be seen that the tolerances of this compensation need not be critical because after the tube 5 has been made sufficiently conductive to actuate the relay 3 slight variations in the charging voltage applied through the resistor 23 to the condenser I3 which would vary the actual total time required for charging the condenser I3 have no effect and are, therefore, negligible.

t has been found in practice that if the supply voltage as drawn from the source I varies as much as 15 percent either way from a mean value, then the charging voltage derived from the potentiometer sections I9 and 2D for placing a positive bias on the grid I while charging the condenser I3 may be held within limits of variation of only about 9 percent above or below normal. This compensation, as will be recognized by those skilled in the art, is provided by the operation of a voltage regulator tube I'I whose grid bias is suitably adjusted by the fixed biasing source 2! in relation to opposing bias of the potentiometer section I9. In adjusting the value of the bat ry 2| and the position of the potentiom er tap 22 for suitable operating conditions, it has been found convenient to first select the location of the tap 22 to give proper timing of the relay 3 when the supply voltage from the source I is normal. After making this adjustment the value of the auxiliary source 2i should be adjusted to give correct compensation of the timing when the supply voltage from the source I attains maximum and minimum values within the permissible range.

Reference to Figure 2 will show how the condenser charging voltage as obtained between the negative side of the source I and the prevailing potential of the cathode in the tube I! can be held within closer limits than the tolerable limits of variation of the D. C. supply voltage itself. The legends supplied in this graphic chart are self-explanatory and are indicative of the relationships between (1) the positive grid voltage supplied simultaneously to the grid "I in the tube 5 and to the condenser I 3; (2) the variations in biasing potential supplied to the grid i through the potentiometer I I when the time delay circuit I2-I3 is shorted out; and (3) variations in plate current in the tube 5 attributable to the control of this tube under the influence of the relay I6 and the operation of the time delay circuit IZ-I3.

It is, of course, to be understood that various modifications of my invention will suggest themselves to those skilled in the art in view of the foregoing disclosure. The illustrated example, together with the values assigned to the components of the embodiment illustrated are, therefore, to be considered as only typical of the general form in which the invention itself may be practiced. The invention itself is, therefore, defined in its scope by the following claims:

I claim:

1. In a circuit arrangement having a time-delay constant, a source of operating potentials, an electron discharge device having input and output circuits, said input circuit having a grid biasing source and a shunt combination of capacitor and resistor in circuit between the cathode and control grid of said discharge device, relay-actuated means for normally short-circuiting said shunt combination while maintaining a cut-off bias on said control grid, said means being operable in response to a signal for removing the short-circuit and for causing said capacitor to be charged and for slowly shifting the bias on said control grid to a less value, and means operable in dependence upon variations in the potential of said source for regulating the time delay constant of said capacitor-resistor combination, thereby to bring said discharge tube to a conductive state after a predetermined delay following the signal response of the first said means.

2. In a device of the class described, a signalresponsive relay having front and back contacts associated with its armature, an electron discharge tube having a plurality of electrodes including a cathode, a control grid and an anode, a cut-oil biasing circuit extending from said grid through said relay armature, its back contact, and a resistor to said cathode, a delay circuit comprising a condenser-resistor combination, across which said relay armature and its back contact form an occasional short circuit, a source of operating potentials for said tube and for charging the condenser of said delay circuit, said relay being operable to apply charging current through its front contact and armature to said condenser, means including a variable impedance connected to the positive terminal of said source and through a fixed impedance to the negative terminal 01 said source for supplying a charging voltage to said condenser upon actuation of said relay, and means associated with said variable impedance for regulating the value of said charging voltage in dependence upon variations in the terminal voltage of said source.

3. A device in accordance with claim 2 and having a translating device in the output circuit of said discharge tube, said translating device being operable after a predetermined delay following the operation of said relay.

4. A device in accordance with claim 2 and further characterized in that said variable impedance is constituted by an electron discharge tube having a control grid connected through a direct current potential source to an intermediate point on said fixed impedance.

5. The combination of two electron discharge tubes one of which possesses means for regulating the operating bias potential applied to the control grid of the other, a source of direct cur rent operating potentials for said tubes, a time constant device in circuit between the cathode and control grid of the second said tube, a-

signal-responsive relay having contacts for alternately short-circuiting the time constant device and then causing the same to receive a charge through the first said tube, a load in the output circuit of the second said tube, and means acting in dependence upon variations in the potential of said source for maintaining the delay action of said time constant device Within prescribed limits,

6. The combination set forth in claim 5 and having three impedance paths across said source, one of said paths including the first said tube in series with a fixed resistor, the second path including the second said tube and the load in its output circuit, and the third path being constituted by a potentiometer having different taps for the cathode and grids, respectively, of the second said tube.

7. A timing circuit arrangement comprising a signal-responsive relay, a condenser-resistor time constant device, an electron discharge tube having a translating device in its output circuit, a variable source of direct current operating potentials, and biasing voltage regulator means including a thermionic device for feeding a control bias potential to said tube, said biasing voltage regulator means in combination with the first said relay and said time constant device being mutually cooperative to maintain the delay action of sai dtranslating device within closer limits of percentage variation than the permissible variations of said source.

HERSCHEL B. MARTIN.

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