Abstract: A printer having a disposable print head which contains a consumable ink supply includes the capability of determining the level of ink in the print head without directly measuring the ink supply. The print head includes a number of resistors which can be driven to an open circuit condition by the printer. The printer includes a counter and memory for tracking the usage of the print head and a driver for selectively driving the print head resistors to an open circuit condition based upon such usage. The printer is also capable of detecting the condition of the resistors on the print head and producing a resultant visual display.

Abstract: An improved DC servo motor driver circuit is provided that is based upon a readily available conventional stepper motor driver integrated circuit (IC). The IC's current "Sense" line that is usually connected to a low value resistor is instead tied to DC common or to ground. The IC's "Comparator" input, which is usually connected to the current Sense line, is connected to a pulsing input signal that provides the comparators with an appropriate voltage to make the comparators believe that more current is required at the very times the remaining portions of the circuit are attempting to provide current to the DC servo motor. An RC circuit is provided at the IC's "Pulse Time" input so that the monostable timer is properly triggered. An ASIC provides the proper logic signals to not only control the direction of the DC servo motor, but also to provide pulses of an appropriate frequency and duty cycle to emulate a pulse-width modulator.

Abstract: A method and apparatus is provided for detection of low to moderate impedance short circuits on any driven line of a thermal ink jet printer to inhibit damage to printer driver circuitry, principally active elements thereof. The printer includes a printhead having a plurality of thermally activated print nozzles therein for ink ejection upon thermal agitation of the ink within the nozzle, and data and address drive lines driven by data line and address line drivers for selection and activation of nozzle heater active elements associated with each of the nozzles by effecting current flow through a heater element associated with each of said nozzles upon selection by associated address and data line activation.

Abstract: A printer having a disposable print head which contains a consumable ink supply includes the capability of determining the level of ink in the print head without directly measuring the ink supply. The print head includes a number of resistors which can be driven to an open circuit condition by the printer. The printer includes a counter and memory for tracking the usage of the print head and a driver for selectively driving the print head resistors to an open circuit condition based upon such usage. The printer is also capable of detecting the condition of the resistors on the print head and producing a resultant visual display.