Light Curtain Cascade Control for Component Reduction
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Solution Overview
Problem
Existing light curtains are costly due to the large number of components required per beam axis for control, with complex central transmission power setting for transmitters and individual control circuits for receivers, leading to high design complexity and costs.
Innovation Solution
The light curtain design features transmitter and receiver cascades with direct individual or group activation using fewer components, eliminating current-limiting resistors and individual preamplifiers, and utilizing a central group amplifier and diode selection switches for receivers, along with a redundant evaluation unit for error detection, to reduce component count and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If individual control circuits with integrated components (ASICs) or discrete components are used for each receiver, then the receivers can be controlled individually, but the device complexity and cost increase significantly
Solution Approach 1:
Multiple receiver control functions are merged into a single control circuit that can sequentially control multiple receivers. The control circuit uses a shift register to generate control signals for individual receiver activation, eliminating the need for separate control circuits for each receiver while maintaining individual control capability.
Solution Approach 2:
The single control circuit is designed to be universal, capable of controlling any receiver in the array through sequential activation. The circuit uses a common control line and shift register mechanism that can address and control multiple receivers, making one circuit perform the function of multiple dedicated circuits.
2Ease of operation
If driver circuits with current-limiting resistors are used for each transmitter, then the transmitters can be controlled individually, but the central transmission power setting becomes extremely complex
Solution Approach 1:
The current-limiting resistors are extracted from the individual transmitter control paths and replaced with a centralized current control mechanism. A single current control line is used to regulate the current for all transmitters, eliminating the need for multiple current-limiting resistors and simplifying the power setting complexity.
Solution Approach 2:
A centralized current control circuit acts as an intermediary between the control unit and multiple transmitters. This intermediary circuit receives a single control signal and distributes appropriate current levels to individual transmitters through a shift register mechanism, simplifying the power setting while maintaining individual control capability.
3Measurement precision
If a large number of components per beam axis are used, then the light curtain can be controlled with high precision, but the cost per beam axis increases
Solution Approach 1:
The control functions are segmented into modular components: a shift register for sequential activation, a common control line for signal distribution, and individual receiver/transmitter elements. This segmentation allows precise control through software/firmware logic in the shift register while using minimal physical components per beam axis, reducing cost while maintaining precision.
Solution Approach 2:
The system changes from using multiple dedicated hardware components per beam axis to using a time-division multiplexed approach where a single control circuit dynamically changes its control parameters (which receiver to activate, when to activate) to achieve precise control. This parameter-based control reduces component count while maintaining detection precision.
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
This design significantly reduces the number of components per beam axis, simplifies the structural design, and meets safety standards while ensuring high reliability and sensitivity, making the light curtain more cost-effective and efficient.
Implementation Method 1
an array of transmitters emitting light beams (3) and with an arrangement of receivers receiving light beams (3)
Implementation Method 2
Each receiver is formed by a receiving diode (6) or a receiving transistor
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The light curtain (1) comprises an arrangement of beam axes forming transmitters and receivers. The emitter forms an emitter cascade. The emitters are activated direct individually or collectively by a trigger circuit without a current-limiting resistor in its current path. The emitting power is centrally predetermined and is adjusted for the individual emitter.