Johnny H Foster

US Patent:

48334065, May 23, 1989

Filed:

Apr 17, 1986

Appl. No.:

6/854062

Inventors:

Johnny R. Foster - Carrollton TX

Assignee:

Household Commercial Financial Services Inc. - Prospect Heights IL

International Classification:

G01N 2772
G01R 3302
H01L 4300
A03K 1790

US Classification:

324225

Abstract:

A temperature compensated Hall-effect sensor apparatus is disclosed which senses the position of a moving body and provides an output signal indicative of the position of the moving body. The apparatus includes a Hall device which senses the application and subsequent removal of a magnetic field and provides an output signal to a constant gain amplifier. Circuitry is provided in the constant gain amplifier for adjusting the gain of the amplifier and also for nulling-out any offset voltage received from the Hall device. The output of the constant gain amplifier is input to a sensitivity compensation and hysteresis circuit for setting a positive-going threshold trip level and a negative-going threshold trip level into a comparator. Circuitry is included which provides both the positive-going and the negative-going threshold trip levels with temperature compensation such that the effective positive and negative trip levels of the comparator remain the same for a given magnetic field and are independent of the temperature of or the signal level out of the Hall device as affected by temperature. Circuitry is provided to change the amount of hysteresis such that the negative-going threshold trip level is a predetermined percentage of the positive-going threshold trip level.

US Patent:

54914124, Feb 13, 1996

Filed:

Jan 24, 1994

Appl. No.:

8/186303

Inventors:

Johnny R. Foster - Carrollton TX

Assignee:

Optek Technology, Inc. - Carrollton TX

International Classification:

G01R 3306
G01N 2772
H03K 1790
H03K 1918

US Classification:

324251

Abstract:

A security circuit includes a Hall-effect sensor for generating an output signal in response to a sensed variation in magnetic field strength. A supply voltage source is connected to the Hall-effect sensor. A latch circuit receives the Hall-effect sensor output signal and generates a latched output signal. The latch circuit operates between a set and a reset state. Circuitry is provided for monitoring the supply voltage source and for generating an output signal applied to the latch circuit. The latch circuit generates the latched output signal in response to the Hall-effect sensor output signal and the output signal generated by the monitoring circuit when the supply voltage is at a predetermined level. The latch circuit is reset when the supply voltage is below the predetermined level.