Nozzle Timing ASIC
The carriage processor dedicates its address/data bus to interface with the nozzle8timing ASIC. The ASIC is also connected to the shuffler ASIC by a synchronous serial channel. The nozzle8timing ASIC applies the shuffled data it receives from the shuffler ASIC to the cartridge drivers, controlling the firing time and sequence of the print8cartridge nozzles.
The outputs controlling the print cartridge drivers are disabled while the reset signal is active. A voltage supervisor monitors the logic supply (+5V) and generates a reset signal to prevent firing nozzles during power transitions. The falling threshold for reset is 4.71V worst case.
Servo Processor Interface
The carriage8processor serial port is used to communicate with the servo processor. The servo processor controls the carriage8processor reset signal.
A/ Converter
The carriage processor controls an eight8channel serial A/D converter. The processor drives the A/D8converter control signals, chip select and shift clock.
Print Cartridges
Nozzle Testing The carriage processor can verify the firing of each print8cartridge nozzle. Firing a nozzle causes a voltage drop at the ballast resistor for that nozzle. A comparator senses the voltage drop at each ballast resistor and outputs a pulse to a processor counter. This enables the processor to determine whether each print cartridge is inserted properly.
Temperature Sensing A thermistor mounted on the carriage PCA allows the carriage processor to sense ambient temperature. The processor can adjust the amount of energy delivered to a print cartridge by changing the nozzle firing time though the nozzle timing ASIC. The plotters compensate for changes in ambient temperature and self heating of the print cartridges based on the data provided by the carriage processor.
Line Sensor
The plotters calibrate the writing system to compensate for alignment errors due to mechanical tolerances using an optical line sensor. The sensor is capable of precisely measuring, within the field of view of the sensor, the position of one line relative to another. The sensor measures both horizontal and vertical line positions. The plotters also use this sensor to determine the location of the media edges in the carriage sweep axis.
Operation The sensor employs a quad photo diode array with illumination from a diffuse LED. A simple optical system employing two lenses forms an image of the test pattern on the photo diode array. A transimpedance amplifier converts the current generated in each photo diode to a voltage. The carriage processor samples the resulting voltage through the A/D converter.
Accuracy The accuracy of the line sensor after self8calibration when measuring lines spaced at 1/300 inches is 0.3 mil. When determining the position of the left or right media edge, the sensor accuracy is 6 mil.
5830 FunctionalOverview | C3187890000 |