Solenoid control system with cusp detector

A control system for actuating a solenoid in response to a signal indicative of an external need therefor and for deactuating said solenoid when the solenoid armature reaches a predetermined position, said control system comprising:

• means for establishing a current path from a source of potential through said solenoid to ground, said path-establishing means including a bistable switching means for opening and closing said current path;
• detector means responsive to the current in said current path for detecting when said solenoid armature reaches said predetermined point and for generating a control signal in response thereto;
• and
• control means responsive to said signal indicative of an external need for triggering said bistable switching means to a first state wherein said current path is closed for energizing said solenoid and responsive to said control signal for triggering said bistable switching means to a second state and opening said current path for de-energizing said solenoid.

A cusp detector circuit comprising:

• current sensing means for sensing the flow of current in a path;
• differential voltage comparator means having first and second inputs and an output;
• first resistor-capacitor means coupled to said first input and to said current sensing means for supplying a first level of voltage to the first input of said comparator means;
• second resistor-capacitor means coupled to said current sensing means and to said second input for establishing a ratio between said first resistor-capacitor means and said second resistor-capacitor means and establishing a voltage differential between the first and second inputs of said comparator means;
• feedback means coupled to the output of said comparator means for preventing oscillations and reducing noise;
• and
• wherein said comparator means responds to a cusp in the current flowing in said current-sensing means for providing an output signal indicative thereof.

An electrical circuit for detecting a fluctuation in the polarity of the slope of an analog current waveform, such as a cusp of the like, which may occur in response to change in reluctance, said detection circuit comprising:

• a current-sensing resistive means for sensing an analog current;
• a first resistor-capacitor means having a first RC time constant and a second resistor-capacitor means having a second time constant connected across said current sensing means for establishing a ratio between said first resistor-capacitor means and said second resistor-capacitor means for sensing the changes in the current flowing in said current-sensing resistive means;
• a differential voltage comparator means responsive to the differential voltage ratio established by said first resistor-capacitor means and said second resistor-capacitor means for generating an output pulse in response to a relatively rapid fluctuation in the current flowing in said current-sensing means;
• and
• means coupled to the output of said comparator means for reducing noise and preventing oscillations.

An electrical circuit for detecting a change in the polarity of the slope of a current waveform comprising:

• a current-sensing resistive means for passing electrical current;
• a first resistor-capacitor means having a first RC time constant;
• a second resistor-capacitor means having a second and different RC time constant;
• means for coupling said first and second resistor-capacitor means in parallel across said current-sensing resistive means and establishing a differential voltage ratio between said first resistor-capacitor means and said second resistor-capacitor means for sensing variations in the current flowing in said resistive means such that a ratio of a first polarity is established when the current flowing in said resistive means is increasing and a ratio of the opposite polarity is established when said current flowing in said resistive means is decreasing;
• a differential voltage comparator means coupled to said first and second resistor-capacitor means and responsive to said differential voltage ratio established thereby for generating a first electrical signal in response to the establishment of a differential voltage ratio of said first polarity and for generating a second electrical signal in response to the establishment of a differential voltage ratio of said opposite polarity;
• and
• means coupled to the output of said comparator means for reducing noise and providing hysteresis.