US2684448A - Controllable pulse generator - Google Patents

Description

y 1954 H. e. NILLES JR CONTROLLABLE PULSE GENERATOR Filed June 3, 1952 Q INVENTOR HERBERT e. NILLES,JR.

ATTORNEY Patented July 20, 1954 UNITED STAT OFFICE GONTROLLABLE Herbert G. Nilles, Jr.,

PULSE GENERATOR Grand Rapids, Mich, as-

tary of the Navy Application June 3,

1 Claim. 1

The present invention relates generally to a controllable pulse generator, and more particularly to a pulse generator wherein the repetition rate and the pulse duration of its output are independently controllable by separate control elements.

It is an object of the invention to provide a non-sinusoidal wave generator wherein the frequency and pulse duration of the wave may be independently controlled.

It is a further object of the invention to provide a pulse generator controlled by relay means and having independent frequency and pulse duration control.

It is another object of the invention to provide thyratron tube means in combination with appropriate amplifier and switching means so that a wave of variable frequency and pulse duration may be obtained.

Other objects and advantages of the present 'ivention will be readily appreciated as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which:

Fig. 1 is a circuit diagram of a preferred modification of the present invention; and

2 is a chart explaining the operation of the present invention.

According to the invention there is provided a triangular wave generator comprising a thyratron tube connected as a cathode-follower across a source of direct current voltage, the cathode resistance producing a sufficiently high voltage drop to reduce the voltage across the thyratron tube below the minimum ionization voltage. A condenser paralleling the cathode resistor prevents an instantaneous increase in the voltage drop across the cathode resistor during the interval of time required to charge the condenser. When the tube is rendered non-conducting by the voltage drop produced across its cathode resister, the condenser discharges through the cathode resistor until sufficient potential difference exists across the tube to again cause conduction therethrcugh. The voltage appearing across the condenser is used to energize a direct current amplifier which controls a relay which operates at a predetermined current through its operating w The portion of each cycle during wt "1 the relay is actuated is dependent upon the gain of the direct current amplifier and it may be varied.

The repetition rate of the thyratron tube is ccntr lled by varying the value of the resistance 1952, Serial No. 291,393

in its cathode circuit. This has no efect on the charging time of the condenser, but it does vary the discharge time and th refore the total length of the cycle of operation. A rheostat paralleling a fixed resistance is provided as a cathode resistor.

Ref rring now to Fig. 1, there is shown an input 2 to rectifier unit 3 which supplies the needed voltages for the pulse generator from a conventional source of power, such as 115 volts, 63 cycles. Glow tube in series with limiting resistor 5 indicates that switch has been closed.

Rectifier unit 3 comprises a transformer having a primary coil 8 and a plurality of secondary coils ii, i2 and 53. The primary coil 8 is ener zed from input 2.

he secondary coil ii sup lies energy to two sets of full wave rectifiers oppositely connected. One set comprises a double diode tube ii that provides a positive potential on conductor it as compared to ground potential on grounded. conductor is? to which the midpoint of coil i i is connected. The 0th ct comprises a pair of diodes 2t and 23 connected. to provide a negative potential on conductor 22 through a resistor 23, the ne ative potential being with reference to the ground potential on conductor Voltage smoothing means of any suitable kind may be provided, as for example the condenser E i and filter 25.

secondary coil 53 supplie heating energy to the cathode heaters of the various tubes shown in a well known manner, the actual connections being omitted in the interests of brevity and clarity.

In order to generate pulses a thyratron tube is provided having an anode 32 connected tlrough a current limiting resis or 33 to the v conductor it, and having a cathode 3 connected through the s es connected cathode resistors and 3%; to the grou .led conductor Their joinig conductor Bl is connected to the control i l of the thyratron tuhe 3i. of the resistors 35 and are ected respectively, to central conductor ii at ground 166 of a few ent conducted by cathode resistances 35 and istancc so that contube will produce such a large de-onize when the grid is made he condenser 32 is connected in par allel with the resistances 35 and 36 to prevent an instantaneous voltage change thereacross, so that the tube 3i remains conductive during the charging interval of the condenser. When the condenser 32 has become charged, the grid 33 of the tube 35 is made negative with respect to the cathode 35 by the voltage drop across the resistance 35, and the voltage impressed on the tube is reduced to the value at which conduction stops.

The negative potential impressed on the grid 56 is maintained until the condenser 32 discharges sufficiently to allow the thyratron tube 34 to ionize again to repeat the cycle, and the discharge time of the condenser is controlled by the resistance in its discharge path. The resistance in the discharge path in controlled by means of the series connected resistance as and the variable resistance l i connected in parallel with the condenser, so that the discharge time may be varied over wide limits. The charging time of the condenser is short with respect to the discharge time thereof, so that the repetition rate of the thyratron is eiiectively controlled by varying the setting of the variable resistance Q4.

The voltage appearing across the condenser a2 is used to control conduction of the tube d which has an anode it connected to the lead 58, and a cathode ill connected through series connected resistor elements :38, 52 and 53 to the movable tap 5c of the potentiometer 55. The potentiometer 55 is connected between the grounded conductor !9 and negative conductor 22 so as to provide an adjustable negative voltage for a purpose later to be described. The condenser 56 is connected between the movable tap 5t and the grounded conductor 89 to prevent appreciable voltage changes from appearing thereacross during the time interval of one cycle. The control grid 51' is connected to the control conductor at.

The tube 65 is normally conducting, since the voltage on the grid 5? is always above ground potential and its cathode is connected to a point below ground potential. When the charge on the condenser 52 increases, the current through the resistances 48, 52 and 53 produce a voltage drop thereacross which raises the potential of cathode ll with respect to ground. This increase in potential controls the operation of the switching circuit consisting of three direct-connected stages operating a double-throw relay.

The tube 58 comprises a cathode 52 connected to ground, an anode 53 connected to conductor it through the resistance 54, and a control grid 65 connected to the movable tap E6 on the resistor element 52. A voltage divider comprising resistances ti and E8 is connected between the anode 63 and the conductor :2 which is connected to the movable tap Ed on the potentiometer 55. The junction of resistances t7 and 63 is connected to the grid E3 of tube 1 3.

The tube 'M comprises a cathode '55 connected to ground and an anode "1G connected through the resistance ii to conductor it. A voltage divider comprising resistances 82 and 33 is connected between the anode 76 and conductor F2. The junction of resistances 82 and 83 is connected through resistance 85 to the grid 8% of tube 8'2. The anode E8 of tube 8? is connected through the con trol winding of the relay 93 to the conductor 53, while the cathode 9 3 is connected to ground.

When the condenser :32 charges, the voltage rise at the movable tap fit of the potentiometer 52 causes the tube 58 to conduct more heavily than before and therefore causes the voltage at the anode 63 of tube 58 to fall in proportion to the voltage rise. This voltage drop is transmitted to tube lI-l which conducts less current so as to cause a voltage increase at its anode l6, and this increase is transmitted to the grid 86 of tube 81 to cause tube Bl to conduct more heavily and thus actuate the contacts 95 of relay 93. Armature 98 swings between contactors 99 and 103.

Adjustment of the movable tap 5 on the potentiometer 55 regulates the bias on tubes 76 and 8? and so regulates the current conducted by the tube 87 through the operating winding 92 of relay 93 when the condenser 42 is discharged. The current through the relay is adjusted to a value considerably below the value at which the relay is actuated, since the tube 3? will conduct heavily when condenser 32 is charged. Resistor is provided to prevent the flow cf appreciable grid current in the tube S'l.

The current conducted by tube 8?, when the condenser 52 is charged, corresponds to the voltage impressed on the grid (55 of tube 58, which voltage is adjustable by varying the setting of the movable tap on potentiometer 52. The magnitude of the charge on condenser 22 is substantially uniform between pulses, so that the point at which the relay 93 closes and opens may be regulated by adjustment of potentiometer 55.

The operation of the circuit may be more readily understood by reference to Fig. 2 in which the curve 95 represents the charge on condenser is plotted with respect to time. The points A represent the voltage at which the thyratron tube 3i ionizes to conduct current. The points B represent the voltage at which the tube 3| becomes non-conducting During the time interval represented by C, the condenser is charging; it is di charging during the time interval represented by D. The actuating voltage of the relay 93 is indicated by the line 9'5. Adjustment of the movable tap 56 has the effect of shifting the curve 96 in a vertical direction so as to vary the time interval E during which the relay is actuated. The cyclic interval H is varied by varying the discharge time D. This is done by varying the setting of the variable resistance 4 It is also to be noted that the output wave shape at contacts 95 is rectangular since armature S3 swings between contactors 98 and lei) on a make or break basis. Assuming that there is a potential difference between armature 93 and contactors 99 and icil, an initial surge of current results when contact is made. There is then a level period of current flow, followed by an abrupt cut on when contact is broken.

It is apparent that novel circuit means have been provided to control the output of a controllable pulse generator. One control means acts to vary the frequency or repetition rate of the wave; another control acts to vary the pulse duration of the signal applied to the output device. By appropriate choice of circuit constants, the pulse duration may be varied between 5% and 95% in terms of make to break ratio.

It should be understood, of course, that the foregoing disclosure relates to onl a preferred embodiment of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claim.

What is claimed and desired to be protected by Letters Patent or" the United States is:

A control circuit including a saw tooth generator, an amplifier and a relay requiring a predetermined actuating current, said saw tooth generator comprising a thyratron tube having an anode, a cathode and a control grid, a source of anode potential connected to said anode, a first and a second resistor serially connected. between said cathode and ground, 1 leans connecting said control grid to the juncture of said first and second resistors, a capacitor connected between said cathode and ground, a variable resistor connected between said cathode and ground, said variable resistor serving to vary the discharge time of said capacitor, said amplifier comprising at least one tube having' an anode, a cathode and a control grid, potentiometer means connecting said capacitor to the cathode-grid circuit of said tube whereby to vary the amplitude of the voltage impressed thereon, and said relay connected in the anode-cathode circuit of said amplifier, whereby said variable resistor varies the cyclic 6 rate of said saw tooth generator and said potentiometer means the duration of the actuating of said relay in each cycle.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,467,415 Woodruff Apr. 19, 1949 2,621,294 Podbielnial: a- Dec. 9, 1952 FOREIGN PATENTS Country Date Great Britain Mar. 26, 1935 OTHER REFERENCES Heini: Abstract of application Ser. No. 594,401, published November 21, 1950, 640 O. G. 1032.

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