Digital potentiometer

Abstract: The present invention discloses an electromagnetic sensing touch screen, which includes a display panel, a sensing capacitor matrix, select units, voltage controlled oscillators (VCOs), digital potentiometers, EM (electromagnetic) wave receive/detection units, a standard EM wave transmit unit and a control unit. A single detection unit consists of a corresponding select unit, VCO, digital potentiometer and EM wave receive/detection unit. The control unit drives the standard EM wave transmit unit to transmit standard EM wave, and further controls the EM wave receive/detection units to receive sensed capacitance values from the sensing capacitor matrix in a scanning manner. As a result, each EM wave receive/detection unit generates a respective detection signal for determining the location of the finger(s) and checking how the finger(s) approaches to or actually touches the sensing capacitor matrix, thereby generating finger location information and implementing the multipoint touch and display function.

Abstract: A stepper motor controller and method for controlling the motion of a stepper motor by selectively energizing the motor's windings so that the current level in the windings match a desired current profile. The motor controller comprises a master logic device, preferably a microprocessor or microcontroller, which is programmed with logic for issuing control signals corresponding to the sequence with which the windings of the stepper motor are energized and the desired current profile. A portion of the control signals are received by a slaved logic device, which is programmed with logic for generating ramp command signals corresponding to the desired current profile. The slaved logic device produces a ramp command signal that is received by a digital potentiometer, which preferably includes an up/down counter. The output signal produced by the digital potentiometer corresponds to a current count value of the up/down counter, and it is controlled by the ramp command signals. By controlling the digital potentiometer with the ramp command signals, a current command signal is produced corresponding to the desired current profile and having a range between low and high reference voltages. This current command signal is provided to a stepper motor drive circuit, which controls the current levels in the stepper motor windings so that they correspond to the desired current profile and are phased according to required sequence.

Abstract: Whereas the memristor can be emulated via digital potentiometer controlled by a microcontroller, a similar implementation of memcapacitor and meminductor is problematic. The paper describes a synthesis of mutators which transform the emulated memristor into memcapacitor and meminductor. The transformations preserve the unambiguous constitutive relations of these elements, which are derived from the constitutive relation of the memristor. An example of the circuit configuration and the simulation results are demonstrated.

Abstract: The development and implementation of a digital-signal-processor (DSP)-based portable impedance-measurement instrument is described. The circuit sinewave stimulus is generated by the device using a direct digital synthesizer at the desired measurement frequency. The sine is applied to a reference impedance in series with the unknown impedance. Two analog-to-digital converters (ADCs) acquire multiple samples of the two sine voltages, which are transmitted to the DSP. Sine-fitting algorithms determine the sine amplitudes, phases, dc components, and frequency. With these values and the reference-impedance values, the unknown impedance amplitude and phase are determined. Amplifiers, which are included in the device, extend the ADCs' input range, while a digital potentiometer enables the adjustment of the reference impedance to improve accuracy.