Printer Photosensor Port Sharing Through Sequential Duty Control
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Solution Overview
Problem
The increasing number of photosensors required for printers strains the resources of the microcontroller unit (MCU), necessitating the use of more expensive MCUs with a large number of ports.
Innovation Solution
A photosensor driving device that uses a controller to output signals with duty ratios to multiple photosensors through a single output port and inhibit input from non-detection targets during signal periods, allowing for reduced port requirements by sequentially controlling and reading outputs from multiple photosensors using shared input and output ports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple photosensors are connected to the MCU with separate ports, then each photosensor can be controlled and read independently, but the number of ports required increases, leading to higher cost and resource strain
Solution Approach 1:
The patent combines multiple photosensor control functions into a single output port by sequentially outputting PWM signals to different photosensors at different time slots. Similarly, multiple input ports are merged into one by sequentially reading the output signals from different photosensors. This time-division multiplexing approach allows one port to serve multiple photosensors, reducing the total number of ports required while maintaining independent control capability.
Solution Approach 2:
The patent implements periodic sequential control by cycling through multiple photosensors in a predetermined order, outputting PWM signals to each photosensor in turn during different time periods. The reading process also follows periodic action by sequentially acquiring output signals from each photosensor in the same cyclic manner. This periodic time-division approach enables efficient resource utilization with fewer ports.
2Device complexity
If sequential control with duty ratios is used, then the number of ports is reduced, but the control and reading process requires careful timing management
Solution Approach 1:
The patent establishes a predetermined sequential order for controlling and reading multiple photosensors before execution. The controller is configured with a fixed sequence that determines which photosensor receives PWM signals and whose output is read during each time slot. This preliminary arrangement of control sequence simplifies timing management by eliminating the need for dynamic scheduling decisions during operation.
Solution Approach 2:
The patent maintains continuous operation by ensuring that while one photosensor is being controlled via PWM signal output, the system is simultaneously or subsequently reading the output signal from another photosensor in the sequence. This continuous cyclic operation through all photosensors ensures no idle time and maintains efficient resource utilization, making the timing management more straightforward as the pattern repeats continuously.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Reduces the number of ports needed for the MCU, enabling the use of less expensive MCUs with fewer ports while efficiently controlling and reading outputs from multiple photosensors, thereby shortening the reading process and improving resource utilization.
Implementation Method 1
a plurality of photosensors 20, 30 each including a light emitting element 21, 31 and a light receiving element 22, 32
Data Source
AI summary
A photosensor driving device includes a plurality of photosensors each having a light emitting element and a light receiving element, and a controller that including an output port commonly connected to light emitting elements of the plurality of photosensors, and a plurality of input ports connected to light receiving elements of the plurality of photosensors, respectively, wherein the controller outputs signals having duty ratios corresponding to the plurality of photosensors to the light emitting elements in order through the output port, respectively, and the controller inhibits an input from a photosensor as a non-detection target in the plurality of photosensors during a period in which the signals are output, and inputs, via the input port, an output of the light receiving element obtained by light emission of the light emitting element in another photosensor as a detection target in the plurality of photosensors.