Fiber-Optic IR Soap Dispenser Sensing Under Ambient Light
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Solution Overview
Problem
Automated battery-operated liquid soap dispensing systems are not robust due to sensitivity to ambient light and high power consumption, leading to inconsistent activation and false triggering.
Innovation Solution
A fluid dispenser system using unpolished plastic fiber optic cables for guiding IR signals, with a microcontroller and comparator to generate and compare voltages, reducing power consumption and improving detection accuracy by accounting for ambient light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high powered infrared sensor is used to detect hand presence, then the detection range and reliability are improved, but the power consumption increases significantly
Solution Approach 1:
The system uses periodic pulsed infrared illumination instead of continuous illumination. The controller activates the infrared LED in short pulses and synchronizes the sensor detection with these pulses, reducing power consumption while maintaining detection reliability through time-gated measurement
2Measurement precision
If the infrared sensor is made highly sensitive to detect reflected pulses, then the detection accuracy is improved, but the sensitivity to ambient light interference increases
Solution Approach 1:
The system continuously measures ambient light levels through the fiber optic cable and dynamically adjusts the detection threshold to compensate for ambient light variations. This continuous adaptation maintains detection accuracy across different lighting conditions
Solution Approach 2:
The controller receives feedback from the sensor about detected light levels and adjusts the pump activation decision based on this feedback. The system compares the detected reflected pulse strength against dynamically adjusted thresholds to distinguish true hand presence from ambient light interference
3Reliability
If multiple pulses are generated for error determination, then the false activation rate is reduced, but the power consumption and response time increase
Solution Approach 1:
The system generates multiple periodic pulses and counts the number of successful detections. By requiring a minimum number of consecutive successful detections out of a small number of pulses (e.g., 2 out of 3), the system achieves robust false activation resistance with minimal additional power consumption compared to single-pulse operation
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
The system achieves reliable and robust operation with significantly reduced power consumption, minimizing false activations and maintaining functionality from complete darkness to full sunlight, including wet conditions.
Implementation Method 1
a fiber optic cable extending to a location proximate the dispensing outlet, a light source for generating a light pulse, the light pulse traveling through the fiber optic cable to the location
Implementation Method 2
If a user's hand is beneath the spout, the pulse generated by the source is reflected back by the user's hand to a photo detector
Implementation Method 3
the light source is an infrared LED
Data Source
AI summary
A method for automated dispensing of a fluid. The method includes providing a light pulse to a location proximate a dispensing outlet from which said fluid will be dispensed, sensing a light received from that location, where the sensed light includes at least one of an ambient light or a reflection of said light pulse, generating a signal corresponding to the sensed light, generating a transistor-transistor logic (TTL) signal if the reflection of the light pulse is determined and pumping a fluid to the dispenser outlet in response to said TTL signal.