US3671817A
Expired / Lapsed
US
⏱️ 0.0 years remaining
High accuracy solid state timer
Assignee: EAGLE SIGNAL CONTROLS CORP A CORP OF DE
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Filing: 1970-12-28
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Granted: 1972-06-20
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Expires: 1990-12-28
Abstract
Abstract A timer circuit consists of a resistance-capacitor charging network with an adjustable potentiometer providing a predeterminable comparison voltage according to the length of time desired and operational amplifier connected as a comparator between the capacitor and the potentiometer providing current gain and high input impedance to prevent loading the capacitor. The non-inverting input of the operational amplifier is coupled to the capacitor and the output of the operational amplifier is fed back to the inverting input of the operational amplifier. A field-effect transistor is provided for discharging the capacitor to zero at the end of the timing cycle in order to avoid the effect of discharge potential difference of other types of discharge devices. A supplemental circuit is provided for illuminating a pilot light precisely during the time that the charging cycle is going on.
Inventors
- 👤 William H Seipp
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 00:10
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/28
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
122 words
A timer comprising in combination first and second directcurrent supply terminals, a resistor and a capacitor in series having a junction terminal, the resistor being connected to the first supply terminal for charging the capacitor through the resistor, a field effect transistor having a drain connected to said junction terminal, a source connected to the second supply terminal and a gate, means for supplying a reference potential, a voltage comparator coupled between said junction terminal and said reference potential source, and timing-period initiating means for turning off the field effect transistor at the beginning of a timing period and means responsive to the comparator for turning the field effect transistor on at the end of a period to discharge the capacitor fully.
Claim 2
Dependent Claim
122 words
A timer comprising in combination first and second directcurrent supply terminals, a resistor and a capacitor in series having a junction terminal, the resistor being connected to the first supply terminal for charging the capacitor through the resistor, a field effect transistor having a drain connected to said junction terminal, a source connected to the second supply terminal and a gate, means for supplying a reference potential, a voltage comparator coupled between said junction terminal and said reference potential source, and timing-period initiating means for turning off the field effect transistor at the beginning of a timing period and means responsive to the comparator for turning the field effect transistor on at the end of a period to discharge the capacitor fully.
Claim 3
Dependent Claim
60 words
A timer as described in claim 1 in which the comparator is a differential amplifier with an input coupled to the said junction terminal and a second input coupled to the said reference voltage source, and the differential amplifier has an output responsive to the condition of substantial equality between the potential at said junction terminal and said reference potential.
Claim 4
Dependent Claim
45 words
A timer as described in claim 2 wherein the differential amplifier is an operational amplifier having a non-inverting input coupled to said junction terminal and an inverting input coupled to said reference potential source and a feedback coupling from the output to the inverting input.
Claim 5
Dependent Claim
72 words
A timer as described in claim 1 having a pilot lamp with an energizing circuit having means for simultaneously energizing the pilot lamp and depressing the potential of the gate of said field-effect transistor to initiate a timing period and for de-energizing the pilot lamp upon charge of the capacitor to reference potentiAl so as to maintain the pilot lamp illuminated during the timing period during which the capacitor is being charged.
Claim 6
Dependent Claim
54 words
A timer as described in claim 3 in which a pilot lamp is provided with an energizing circuit and means are provided responsive to the output of the operational amplifier for simultaneously de-energizing the pilot lamp energizing circuit and raising the potential of the gate of the field-effect transistor to discharge said capacitor fully.
Claim 7
Dependent Claim
83 words
A timer as described in claim 5 in which an output circuit is provided including an electronic control device and a resistor in series, the control device having a control electrode coupled to the output of the operational amplifier, said discharge device and said resistor having a junction terminal and means coupled to said junction terminal for extinguishing the pilot lamp energizing circuit when current is passing through said resistor and actuating said energizing circuit when no current is flowing through said resistor.
Claim 8
Dependent Claim
49 words
A timer as described in claim 6 in which a second operational amplifier is provided which is connected as a differential amplifier having non-inverting input coupled to the capacitor and an inverting input with a feedback connection and an output coupled to the input of the comparator operational amplifier.
Claim 9
Dependent Claim
67 words
A timer as described in claim 7 wherein the output circuit includes a second discharge device in series with the first discharge device interposed between said first discharge device and said discharge circuit resistor and having a control electrode connected to said first direct-current input terminal, whereby energization of the control electrode of the first output circuit discharge device provides anode current for the second discharge device.
Claim 10
Dependent Claim
92 words
A timer as described in claim 8 wherein a failsafe discharge device is providing having an anode and a cathode connected to the control electrodes of the first and second output circuit discharge devices, respectively, and having a control electrode coupled to the gate of the field-effect transistor for short-circuiting the control electrodes of the first and second input circuit discharge devices and biasing said discharge devices to off condition whenever the potential of the gate of the field-effect transistor is raised to turn on said field-effect transistor and discharge the capacitor.
Claim 11
Dependent Claim
71 words
A timer as described in claim 9 wherein an initiating terminal is provided which is coupled to the gate of the field-effect transistor and to the control electrode of the failsafe discharge device and is normally biased to the second direct-current supply terminal, and an initiating circuit is provided which comprises means for depressing the potential of said initiating terminal to turn off said field-effect transistor and said failsafe discharge device.
Claim 12
Dependent Claim
23 words
A timer as described in claim 10 in which the pilot lamp is provided with an extinguishing device coupled to said initiating terminal.
Claim 13
Dependent Claim
40 words
A timer as described in claim 11 wherein the pilot lamp extinguishing device comprises a discharge device having a control electrode coupled to said initiating terminal and to the junction of said second output circuit discharge device and said resistor.
Claim 14
Dependent Claim
38 words
A timer as described in claim 11 wherein pilot lamp extinguishing device comprises a discharge device connected in parallel with the extinguishing device and the pilot lamp is connected to its energizing source in series with a resistor.
Claim 15
Dependent Claim
31 words
A timer as described in claim 10 wherein the initiating circuit comprises a switch connected between said initiating terminal and a point at lower potential than the first direct-current supply terminal.
Claim 16
Dependent Claim
35 words
A timer as described in claim 14 wherein the initiator switch comprises a discharge device having a control electrode adapted to be connected to a point at higher potential than said second direct-current supply terminal.
Claim 17
Dependent Claim
45 words
A timer described in claim 6 wherein the pilot lamp is an incandescent lamp and a discharge device is conneCted in series with said lamp and the energizing circuit therefore, having a control electrode and the lamp extinguisher means is connected to said control electrode.
Claim 18
Dependent Claim
39 words
A timer as described in claim 2, in which the comparator is so connected as to produce a relatively low output prior to the attainment of substantial equality between the potential at said junction terminal and said reference potential.
Claim 19
Dependent Claim
57 words
A timer as described in claim 2, in which the comparator is so connected as to have a relatively high output until the potential at said junction terminal attains substantial equality with the potential at the reference potential and to fall to a relatively low value after the potential at said junction terminal exceeds said reference potential.
Claim 20
Dependent Claim
45 words
A timer as described in claim 17, in which relay means is provided having a control electrode coupled to the output of the comparator and switch means connected to said control is provided for inactivating said relay means until the beginning of the timing period.
Claim 21
Dependent Claim
49 words
A timer as described in claim 18, in which relay means are provided having a control electrode coupled to the output of said comparator with means for normally forward biasing said control electrode which is insufficient to overcome the effect of occurrence of relatively low output of said comparator.
References Cited (Backward Citations)
US3192449A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-06-20 | 1975-12-20 | 1976-06-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-06-20 | 1979-12-20 | 1980-06-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-06-20 | 1983-12-20 | 1984-06-20 | $7700.00 | Window Closed / Lapsed |