Short duration PTC resistor timer

Details Short duration PTC resistor timer Short duration PTC resistor timer

1982-09-09

1984-06-05

Lall, Parshotam S.

Internal-combustion engines

Starting device

For airplane

123179BG, 338 23, 338 25, 361165, 219505, F02N 1700

Patent

active

044521910

ABSTRACT:
A short duration timer for use in an electronic circuit such as a diesel engine glow plug control includes a first PTC resistor energized by an electric power source and stabilized in the exponential portion of its resistance-temperature curve. A second PTC resistor in thermal contact with the first is energized at time zero from the electric power source and substantially immediately stabilizes at a temperature higher than that of the first, resulting in heat flow from the second PTC resistor to the first, and therefore an increase in the resistance of the first, at a rate which is substantially independent of variations in ambient temperature and supply voltage of the electric power source. A signal ending the time duration is generated when the resistance of the first PTC resistor has changed by a predetermined percentage. In a preferred embodiment, a third PTC resistor having a resistance-temperature characteristic substantially identical with that of the first is at least partially thermally isolated therefrom and connected in electrical series therewith to stabilize similarly. In this embodiment the end of the time duration is signalled when the resistance ratio of the first and third PTC resistors equals a predetermined value. The resulting time duration is substantially independent of variations in ambient temperature and supply voltage.

REFERENCES:
patent: 3307167 (1967-02-01), Race
patent: 3486080 (1969-12-01), Tillmann
patent: 3600118 (1971-08-01), Hirsbrunner
patent: 3673538 (1972-06-01), Faxon
patent: 3828292 (1974-08-01), Grossman et al.
patent: 3916264 (1975-10-01), Berg
patent: 4316080 (1982-02-01), Wroblewski

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