Hewlett-packard Company

Hewlett-packard Corporation

George Barbehenn

Huston W Rice

Steven B Elgee

Jason M Quintana

Ross R Allen

Rajeev Badyal

Martin K Mason

Robert Paul Callaway

James R Hulings

John T Eaton

Michael B Saunders

A position encoder system is provided, the system employing a medium having a track with incremental markings which define an embedded reference position identifier. Upon movement of the medium, a sensor detects passage of the incremental markings, each such marking being indicative of a predetermined movement of the medium. The sensor also detects the embedded reference position identifier, and correspondingly, provides a recognizable index pulse for use in determining an absolute position of the medium.

Single channel incremental position encorder with incorporated reference

An AC-DC switching converter converts AC mains power into regulated DC power into a load. It is desired to electrically isolate the load from the mains, and this requires isolation in both the forward power transfer path and the reverse feedback path. The forward path is isolated by use of a transformer, and the feedback signal is transferred through an optocoupler. In a typical pulsewidth modulation control loop design, it is difficult to achieve good loop dynamics when using low cost optocouplers, because of the wide variation of their transfer function gain. However, in the disclosed invention, the loop is operated as a nonlinear limit cycle ('bang--bang') controller. In this mode, the optocoupler gain variation has an insignificant effect on loop operation. The converter switching signal is provided by an inexpensive 555 timer oscillator, and the optocoupler is connected to the reset pin of this timer to turn it ON and OFF in short bursts, as is characteristic of this type of controller. Since a converter must operate over a mains voltage range of about 3:1, the disclosure also includes a technique for protecting the transformer from possible saturation by narrowing the oscillator pulses as an inverse function of the mains voltage.

Simplified AC-DC switching converter with output isolation

Disclosed herein is a motion monitoring system for monitoring movement of a brush-type DC motor. The system includes an electrical comparator having first and second differential inputs. A current detector is connected to provide a drive current signal to the first differential input of the comparator. A low-pass filter is connected to provide an averaged drive current signal to the second differential input of the comparator. When a drive current is applied to the motor, the comparator produces a stream of binary logic-level pulses corresponding to motor movement. The pulses can be used to determine motor position and velocity.

Inexpensive motion control using DC motors

The present invention relates generally to inkjet printing mechanisms, and more particularly to an ultrasonic method for monitoring the ink level in an ink reservoir for an ink jet cartridge. This ultrasonic method includes the steps of sending an ultrasonic signal towards the ink reservoir, and receiving a series of reflected ultrasonic signals from the reservoir. In a processing step, the series of received reflected ultrasonic signals are processed in order to determine the ink level in the reservoir.

Ultrasonic method for monitoring inkjet cartridge levels

In thermal inkjet printing, an energy source supplies voltage pulses to a set of resistors in a printhead. The resistors are not necessarily equal-valued. The subset of energized resistors changes from pulse to pulse as a function of the printable data. As the subsets vary, resulting in a varying load on the energy source, this causes undesirable variations in the energy supplied to individual resistors, even when a regulated source is used, because of residual impedances in the source and wiring. The invention compensates for such energy variations, using information about which subset of resistors is to be energized during a pulse. By determining the electrical load presented by the subset, and by referring to a predetermined relation between the load value and the voltage drop in the residual impedances, the invention maintains nominally constant energy in individual pulsed resistors by an appropriate adjustment of the pulse width.

Reducing energy variations in thermal inkjet printers

A switching DC-DC converter, with regulation of the output, is disclosed. Unlike prior art converters, the source of the switching signal is not a free-running oscillator, but a rectangular waveform whose frequency and duty cycle parameters are under the control of an external processor. By appropriately varying these parameters, the processor dynamically modifies the characteristics of the converter, in effect optimizing its design to deal efficiently with different operating states such as circuit startup, sudden load changes the processor 'knows' about in advance, and even design changes over the life of the converter. Once the processor sets up appropriate parameters for an existing or anticipated state, a hardware feedback loop regulates the output voltage of the converter by reducing the width and/or number of switching pulses. Thus, the processor is not part of the voltage regulation process but is free to devote attention to other parts of the system in which the converter resides.

DC-DC converter with dynamically adjustable characteristics

In DC-DC switching converters of the single-ended primary inductance (SEPIC) type, using a high frequency transformer to isolate the load from the AC power line is difficult because its leakage inductance causes serious circuit problems. In the invention, an additional coupling capacitor provides the required DC isolation without affecting circuit performance. The total coupling capacitance may be chosen to limit the power line frequency leakage current to a safe value.

Sepic converter with transformerless line isolation

An integrated circuit for use in the printhead of an ink jet printer includes an array circuit for heating an ink reservoir to produce a pattern of ink jets, the array circuit including a plurality of resistor cells arranged into rows and columns. A corresponding number of row and column lines are coupled to the integrated circuit array for selecting and energizing the resistor cells according to the desired printing pattern. An identification circuit integrated into the same substrate as the array circuit includes one or more programmable paths, the programmable paths corresponding and coupled to each row line. The programmable paths each include the serial combination of a programmable fuse and an active device. The opposite end of the programmable paths are coupled together at a common node, which in turn is coupled to an output circuit for providing a single output signal in response to a polling of the row lines. The identification circuit can be programmed and polled without adversely affecting or energizing the array circuit.

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Vancouver, WA, United States of America

George Barbehenn