Trw Limited

Xolox Corporation

Joel C Van Antwerp

Larry L Harris

A transducer in the form of an integrated circuit comprising a Hall cell, first and second differential amplifiers, an output driver stage, a threshold voltage-generating circuit between said amplifiers, and a control circuit for selectively enabling and disabling the threshold voltage-generating circuit. The second amplifier provides an output signal representative of the enabled-disabled condition of the threshold voltage-generating circuit. A permanent magnet having a temperature coefficient is movable with respect to the transducer between given field-applying and field-removing positions. The transducer operates to change switching states between 'operate' and 'release' in response to the two different levels of applied magnetic fields, respectively, resulting from the two given operating positions of the magnet. The transducer also has a temperature coefficient at its 'operate' point which substantially tracks that of the magnet, thereby rendering the transducer operation essentially independent of ambient temperature changes.

Hall-type transducing device

Hall-effect position 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 predetermined number of Hall-effect sensors which are positioned in a straight line and in operating proximity to a moving body made of a ferromagnetic material. A permanent magnet is operatively positioned such that the Hall-effect sensors lie in the magnetic field produced by the magnet while the moving body provides a portion of the path comprising the magnetic excitation circuit with the permanent magnet. The moving body includes portions devoid of ferromagnetic material, which causes a change in the magnetic field. The Hall-effect sensors sense the absolute value of the magnetic field and because of their particular physical alignment and separation, together with the unique interconnection of their individual electrical outputs, provide signals to amplifier devices which represent the second time derivatives of the magnetic field sensed by the Hall-effect sensors. The electrical outputs of the amplifier devices are provided to a Schmitt trigger comparator which performs the analog to digital conversion of the input signals and provides a digital logic output signal which provides a reference point with respect to the location on the moving body, of the void which causes the change in the magnetic field.

Hall-effect array for sensing second spatial derivative of magnetic field

Automatic brightness control apparatus for providing real time control of the brightness of various types of displays while also providing ambient light compensation is disclosed which includes a photodiode for providing a current proportional to the ambient light level. Amplifiers, together with a load, change the photodiode current to a control voltage indicating the level of ambient light. The control voltage is provided as a reference input to a voltage comparator. The other input to the voltage comparator is the output of a free running ramp oscillator. The pulse width modulated logic signal comprising the output of the voltage comparator is provided as the input for an output driver whose pulse stream output is used to control the brightness of the designated display. The duty cycle of the pulse stream output varies with the ambient light level. Several logic gates are added to the free running ramp oscillator to provide synchronization capability and assure that the ramp output waveform of the ramp oscillator will always begin with an incoming synch pulse. The automatic brightness control apparatus is packaged as a monolithic integrated circuit on a single silicon chip which is housed in a clear plastic 8 pin DIP.

Growing community of inventors

Frisco, TX, United States of America

Joel C Van Antwerp