Abstract: Electronic control circuitry is provided for controlling the actuating current of electromagnetic devices and in particular of the electromagnetic fuel injection valves of an internal combustion engine. In order to program the magnitude of the actuating current from an initial high level to a lower maintenance level, there is provided a driver circuit which receives fuel injection control pulses from a fuel injection system, not itself part of the invention, and processes these control pulses into valve-actuating current pulses. The valve current is sensed by suitable transducer, for example a resistor, and the resulting signal is fed to a two-point controller which suitably alters the input to the driver circuit to thereby change the valve actuating current. The set-point value on which the two-point controller operates is itself subject to change by means of a suitable circuit.

Abstract: Comparator means respond to the current levels through an inductive load to generate HIGH and LOW level outputs causing first switch means to connect and disconnect power to the load. When the load current initially exceeds a peak load actuation level, flip-flop means responsive to the corresponding change in comparator output levels change the current through an auxilliary sense resistor coupled to the sense input of the comparator means. In one embodiment, a one-shot multivibrator prevents a change in the current to the auxilliary sense resistor for a fixed period after the commencement of a load actuation signal. The subsequent HIGH and LOW comparator output levels are fed back to the comparator reference input to switch the reference voltage thereat so as to represent first and second levels of the current sufficient to maintain actuation of the load.

Abstract: A circuit is described for energizing an electromagnetically operated fuel injector from an unregulated voltage source in response to an injection command pulse. The injector pull-in current is provided by directly coupling the unregulated voltage across the injector upon the initiation of the injection command pulse. The injector current is thereafter reduced to a lower hold-in value. The circuit is voltage compensated by a pair of timers the first of which compensates for the voltage dependent injector pull-in time by adjusting the time that the unregulated voltage is directly applied across the injector as a function of the value of the unregulated voltage to insure that the injector is energized for all values of the unregulated voltage while minimizing the time period that the unregulated voltage is directly coupled across the fuel injector.

Abstract: Device for controlling by means of a current program a plurality of solenoid valves operating independently. Each solenoid is provided with a current flow control circuit having two inputs. The first input receives a first control signal which determines the duration of each actuation of the corresponding solenoid valve. The second input receives a second control signal derived from the first signal and of lesser duration. The current flow control circuit then provides a pull current to actuate the solenoid in response to these input signals.

Abstract: There is disclosed a method and apparatus for reducing the power required to activate the soft and playing mechanism of an electronic player piano and similar instruments. In accordance with the invention, full voltage on the solenoid is maintained for a short period of time which is more than sufficient to allow full travel of the solenoid and then the power is reduced by reducing the applied voltage. In accordance with the preferred embodiment, a timer is started when the solenoid is commanded on and then when the timer times out, the command gate signal is turned on and off with a waveform which can be set at a duty cycle sufficient to maintain the solenoid in the held-in position.

Abstract: A protective circuit for an electronic switching amplifier is controlled by an operating switch, the amplifier serving to turn on an electromagnet with timed pulses during its operating interval. The electromagnet may electromagnetically actuate positioning and actuating elements on sewing machines and the like, with the timed pulses. A cutoff voltage limiting circuit is connected on one side between the electromagnet and the switching amplifier. A free-running diode is connected in parallel with the electromagnet through an electronic switch as an additional cutoff voltage limiting circuit. The electronic switch is caused to conduct by the switching amplifier during the operating interval, at least during the decay of the timing pulses. The electronic switch is blocked when the operating interval is terminated by the operating switch. The cutoff voltage limiting circuit is designed to conduct when electronic switch is blocked.

Abstract: In an apparatus for controlling an electromagnetic valve which is adapted for use with the fuel injection systems of internal combustion engines, after the expiration of a predetermined time the control of the energization of the electromagnetic coil of the electromagnetic valve is changed from constant-voltage control to constant-current control, and any surge voltage caused during the control change is selectively absorbed, thereby ensuring stable energization of the electromagnetic valve despite variations in the supply voltage or the like.

Abstract: A square-wave signal generator circuit for generating a rectangular waveform signal particularly for application to the field coil of an electromagnetic flow meter. A coil excitation current from a direct current source is switched to provide a current flow in alternate directions through the field coil. During the transient time of the coil excitation current following the switching operation, a higher output voltage from the source is used to shorten the current rise and fall times while a lower voltage from the source is used during a steady state time of the excitation current to minimize power losses. A switching circuit using a switching transistor is used to select the higher voltage while a back-biased diode is used to immediately introduce the lower voltage when the excitation current has reached a steady state.

Abstract: Control system for an electromagnet having a movable core, wherein a power winding is provided for moving the core to active position and a holding winding requiring less power maintains the core in active position. A transistor controls the power supply circuit and, when made conductive, energizes a transistor in series with each winding, thus energizing both windings. After a time delay provided by a resistor-condenser circuit, another transistor is energized which causes the transistor in the power winding to become non-conductive, thus de-energizing the power winding. De-energizing the control transistor causes the transistor in the maintenance winding to become non-conductive so that the maintenance winding is de-energized and its energy is dissipated through a Zener diode and a resistor, both in series therewith.

Abstract: A constant current is applied through a heater by means of an electrical connector which mates with terminal pins of the tube. The applied current causes a voltage across the heater. A first voltage measurement is made across the heater at a first time. After a predetermined time interval has elapsed, a second voltage measurement is made across the heater. The value of the first voltage measurement is substracted from the value of the second voltage measurement and the value of the difference obtained is compared with a predetermined reference value. If the difference value is less than the reference value, a first nominal value of heater resistance is indicated. If the difference value is greater than the reference value, a second nominal value is indicated. The nominal heater resistance values are detected independent of the electrical connector contact resistance.