US3206650A - Interval timer - Google Patents

Description

Sept. 14,1965

Fi ure 1 Filed June 18, 1962 F. A. MILLER ETAL INTERVAL TIMER :ILOAD 6 Sheets-Sheet 1 INVENTORS Frederick A. Miller David E. Earls ept- 1965 F. A. MILLER ETAL 3,206,650

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F. A.- MILLER ETAL Sept. 14, 1965 INTERVAL TIIER 6 Sheets-Sheet 3 CwN N vvv Filed June 18. 1962 I INVENTORS Frederick A. Miller David E. Earls Fi ure 4 Sept. 14, 1965 F. A. MILLER ETAL. 3,206,650

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J L I r s m A N Ill IL j I (5 INVENTORS Frodurlck A. Miller David E. Earls United States Patent 3,206,650 INTERVAL TIMER Frederick A. Miller, Indianapolis, Ind., and David E. Earls, Norwalk, Conn., assignors to P. R. Mallory'& Co., Inc., Indianapolis, Ind., a corporation of Delaware Filed June 18, 1962, Ser. No. 203,232 3 Claims. (CL 317-442.)

This invention relates to electronic timers and in particular to an electronic timing circuit that provides a pulse output for a predetermined time' interval, which output may be used for controlling a relay, solenoid, or other electro-mechanical or electronic devices.

It is another object of this invention to provide a simple timing circuit which is stable over wide limits of temperature and input voltage.

A further object of this invention is to provide a timing circuit which is adjustable over a range of milli- 'seconds to minutes.

It is a further object of thisinvention to provide a timing circuit which has virtually no stand-by power requirements.

It is a further object of this invention to provide a timing circuit which utilizes a neon lamp in conjunction with a photo-resistor in a bridge circuit, which provides sufiicient energy for de-energizing a low cost, general purpose relay.

It is a further object of this invention to provide a timing circuit which eliminates the problem of dark effect which effect tends to increase the breakdown voltage of the neon lamp, thereby affecting the time interval.

It is a further object of this invention to provide a timing circuit which may be practically immediately recycled. It is a further object of this invention to provide a timing circuit having all the above features at low cost.

Among the improved features disclosed in the present invention are:

(1) A bridge circuit incorporating a relay.

(2) Means for unbalancing the circuit to operate a relay.

(3) Voltage regulating means to stabilize the circuit.

(4) Means to overcome a dark efiect in a neon tube which is triggered to unbalance the bridge circuit incorporating the output relay.

(5) A momentary output switch which is manually operative to start a timing cycle.

FIGURE 1 is an electrical schematic illustrating the basic circuit of the present invention.

FIGURE 2 is a modification of FIGURE 1 permitting the reduction of an are that may develop in a lamp and means for completely discharging a ,capacitor.

.FIGURE 3 is a modification of the circuit of FIGURE 2 permitting voltage regulation.

FIGURE 4 is a modification of FIGURE 3 including a bridge circuit having a photoresistor and a.relay coil and a means to overcome the dark effect of a lamp.

FIGURE 5 is a modification of the circuit of FIGURE I 4 without voltage regulation but including a reset means.

FIGURE 6 is an interval timer including an adjustable time means.

Referring now to the drawings, the basic circuit is shown in schematic FIGURE 1.- A DC. power supply of value E which must be greater than the breakdown with two important additions.

3,206,650 Patented Sept. 14, 1965 tothe load. Resistor 8 normally would not supply sufficient current to maintain conduction of lamp 12. As a result lamp 12 will extinguish in a short time, and the cycle will repeat, except starting from a voltage point on the RC. curve corresponding to the extinguishing voltage of lamp 12. Thus, if E is held constant, the pulse rate will be constant except for the first pulse period, which 'will be longer than the rest.

Improvements to and modification of FIGURE 1 are shown in schematic FIGURE 2. In the circuit of FIG- URE 1 an arc may develop in the lamp 12 under certain conditions. Resistor 11 precludes these conditions. It also reduces the change of characteristics of lamp 12 with use. It also allows capacitor 9 to maintain conduction in lamp 12 for longer time, thus producing an output pulse of greater energy. Relay or solenoid contacts 21, 22 and 23, operated by relay coil 15, allows capacitor 9 to discharge completely through resistor 10, which is used to limit the discharge current, thus preventing'weldingof contacts 21 and 23. By completely discharging capacitor 9, the pulse rate is kept constant and equal to the otherwise longer first period. Schematic FIGURE 2 also shows a DC. power supply consisting of diode 2, filter capacitor 4 and current-limiting resistor 1, which supply allows the pulse timing circuit to be energized from the AC. mains E through the DC. power supply. Relay or solenoid coil 15 also operates contacts 24, 25, and 26 to obtain a higher-powered output.

Since the time between pulses depends basically upon the resistance of resistor 8, the capacitance 'of capacitor 9, the breakdown voltage of lamp 12, and the voltage E of the power supply, and since the mentioned values of 8, 9, and 12 are essentially constant, the most important factor tending to produce varying pulse rates is the voltage E SchematicFIGURE 3 is similar to the preceding circuit except for the addition of a voltage regulator. The basic network for regulation consists of resistor 5 in series with two series-connected gas lamps, 6 and 7. Lamps 6 and 7 tend to burn at a constant voltage of about 55 volts each. Therefore E tends to be a constant volts and any voltage fluctuations of E, are absorbed by the resistor 5. Capacitor 3 is used to extend the lower limit of input voltage which will initiate conductionhence regulation-by lamps 6 and 7. The following explanation of how this is accomplished may be correct. When E is a positive value greater than the breakdown voltage of lamp 7, lamp 7 will conduct for a period long enough to cause capacitor 3 to acquire a charge sufficient to cause extinction of lamp 7. This cycle may be repeated as long as E is increasing in a positive direction. This action will leave point A charged negatively with respect to E and leave lamp 7 in a recently-conducting state. As E goes increasingly negative from the peak positive voltage, it will reach the point where the voltage on capacitor 4 plus the voltage on capacitor 3 minus the decreasing voltage E will equal the breakdown voltage of lamp 6. The net results are that both lamps are ignited each shortly after the other, making available ions which decrease the breakdown voltage, and the voltage stored on capacitor 3 is of such polarity as to aid the supply voltage in obtaining breakdown.

Schematic FIGURE 4 is, similar to the foregoing'but One addition is a bridge circuit includng the photoresistor l6 and the relay coil. The purpose of the bridge is to allow the light pulse from lamp 12 to control the point at which a relay or other device terminates an active timed cycle instead of merely pulsing this same device.v WithE applied and after momentarily-closing contacts 18, 19, and 20, a DC. voltage -will be appliedtothe bridge. Since resistors 3 13 and 14 are of equal value, the resistor 17 is of much lower value than darkened photor'esistor 16, the bridge is highly unbalanced and a holding current will pass through coil 15. When lamp 12 flashes, the bridge will be momentarily balanced and the relay having coil 15 will drop out'ending the timed interval.

' In the circuit of FIGURE 3 there is a device peculiarity which may greatly degenerate the accuracy of the timed period. This peculiarity is the dark effect of the lamp 12 which effect increases the breakdown voltage of a gas lamp which has been left inoperative in the dark for a period of time. To eliminate or greatly reduce this efiect a small capacitor 27 is placed in the circuit in such a manner that it will become charged to peak line voltage when the circuit is not in a timing cycle. Upon closing contacts 18 and 20 this charged capacitor is placed across lamp 12 very briefly igniting it thereby allowing only the timed interval for lamp 12 to acquire a dark effect.

Schematic FIGURE shows a similar interval timer but without voltage regulation but including a set of contacts 29 and 30 which are normally open during the timed interval and which may be momentarily closed during the timed interval to reset the timer to the start of the interval. The contacts merely connect the low-valued resisor across the timing capacitor 9.

Schematic FIGURE 6 shows an interval timer having some of the aforementioned features and having an adjustable voltage divider with which an adjustable inter-- val may be had. Practical considerations include a limit on adjustable divider 31 to insure that the voltage available to the timing network will always exceed the breakdown voltage of lamp 12.

There are numerous modifications and changes that may be made in the present invention without departing from the scope thereof. We do not intend to be limited to the exact details shown and described, but only insofar as defined by the scope and spirit of the appended claims.

What is claimed is:

1. An electrical timing circuit comprising: a'triggering circuit including a normally disabled gas diode, a time constant network including a resistor and capacitor, said capacitor being connected in parallel with said gas diode, a direct current power supply feeding said time constant network with 'suflicien-t voltage to cause said gas diode to fire after a predetermined time interval, alight sensitive detector coupled to said gas diode to provide a higher powered output, said light sensitive detector connected as one leg of an electrical bridge, said bridge comprising resistances for the other three legs, a coil of an .electromechanical device connected between opposite pairs of legs of said bridge, means .for momentarily switching a low impedance across that leg of said bridge which is adjacent to said light sensitive detective leg which said two legs form a circuit parallel to said coil, said switching means causing a bridge imbalance 'sufiicient to cause said coil to be fully energized when a direct current voltage of suitable value is impressed upon said bridge, said legs and said voltage being of such value so .as to provide holding current for said coil when said light sensitive detector is not illuminated and to provide no holding current or a small value of reverse current when said light sensitive detector is illuminated, second switching means for momentarily connecting said power supply to said circuit, a third switching means for connecting said power supply to said circuit whenever said coil is sufficiently energized.

2. The circuit of claim 1, wherein a fourth switching .means connects one side of said first capacitor through References Cited by the Examiner UNITED STATES PATENTS 2,867,754 1/59 OBleness 317-142 2,999,208 9/61 Ruehlemann.

3,107,320 10/63 Brittain et a1. 317148.5 3,136,926 6/64 Smith 3l7142 XR OTHER REFERENCES- Electronics at Work in the Home, Service Dept., The Maytag Co., 1960.

SAMUEL BERNSTEIN, Primary Examiner.

MAX L. LEVY, Examiner.

Claims (1)

1. AN ELECTRICAL TIMING CIRCUIT COMPRISING: A TRIGGERING CIRCUIT INCLUDING A NORMALLY DISABLED GAS DIODE, A TIME CONSTANT NETWORK INCLUDING A RESISTOR AND CAPACITOR, SAID CAPACITOR BEING CONNECTED IN PARALLEL WITH SID GAS DIODE, A DIRECT CURRENT POWER SUPPLY FEEDING SAID TIME CONSTANT NETWORK WITH SUFFICIENT VOLTAGE AS CAUSE SAID GAS DIODE TO FIRE ATER A PREDETERMINED TIME INTERVAL, A LIGHT SENSITIVE DETECTOR COUPLED TO SAID DIODE TO PROVIDE A HIGHER POWERED OUTPUT, SAID LIGHT SENSITIVE DETECTOR CONNECTED AS ONE LEG OF AN ELECTRICAL BRIDGE, SAID BRIDGE COMPRISING RESISTANCES FOR THE OTHER THREE LEGS, A COIL OF AN ELECTROMECHANICAL DEVICE CONNECTED BETWEEN OPPOSITE PAIRS OF LEGS OF SAID BRIDGE, MEANS FOR MOMENTARILY SWITCHING A LOW IMPEDANCE ACROSS THAT LEG OF SAID BRIDGE WHICH IS ADJACENT TO SAID LIGHT SENSITIVE DETECTIVE LEG WHICH SAID TWO LEGS FORM A CIRCUIT PARALLEL TO SAID COIL, SAID SWITCHING MEANS CAUSING A BRIDGE IMBALANCE SUFFICIENT TO CAUSE SAID COIL TO BE FULLY ENERGIZED WHEN A DIRECT CURRENT VOLTAGE OF SUITABLE VALUE IS IMPRESSED UPON SAID BRIDGE, SAID LEGS AND SAID VOLTAGE BEING OF SUCH VALUE SO AS TO PROVIDE HOLDING CURRENT FOR SAID COIL WHEN SAID LIGHT SENSITIVE DETECTOR IS NOT ILLUMINATED AND TO PROVIDE NO HOLDING CURRENT OR A SMALL VALUE OF REVERSE CURRENT WHEN SAID LIGHT SENSITIVE DETECTOR IS ILLUMINATED, SECOND SWITCHING MEANS FOR MOMENTARILY CONNECTING SAID POWER SUPPLY TO SAID CIRCUIT, A THIRD SWITCHING MEANS FOR CONNECTING SAID POWER SUPPLY TO SAID CIRCUIT WHENERVER SAID COIL IS SUFFICIENTLY ENERGIZED.

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