Fluid Dispenser IR Sensing for Ambient Light Rejection
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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 unreliable activation of the pump, with issues of false activations and high energy usage.
Innovation Solution
A fluid dispenser system utilizing unpolished plastic fiber optic cables for guiding IR signals, with a microcontroller and operational amplifier to generate and compare voltages, reducing power consumption and improving detection accuracy by accounting for ambient light, and using a low-power IR LED for precise pulse generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high powered infrared source is used for sensing, then detection capability is improved, but power consumption increases
Solution Approach 1:
The system uses periodic pulsed infrared illumination instead of continuous illumination. The microcontroller generates periodic infrared pulses that illuminate the target area, and the photodetector samples reflected light synchronously with these pulses. This periodic action maintains detection capability while significantly reducing average power consumption compared to continuous operation.
Solution Approach 2:
The system employs feedback through synchronous sampling and signal processing. The microcontroller coordinates the infrared pulse generation with the photodetector sampling, creating a feedback loop that optimizes detection timing. This allows the system to achieve reliable detection with lower peak power requirements by precisely timing the measurement window to coincide with pulse reflection.
2Reliability
If conventional infrared sensor is used, then sensing function is achieved, but system becomes sensitive to ambient light
Solution Approach 1:
By using periodic pulsed infrared illumination with specific timing, the system creates a temporal signature for the infrared source. The photodetector samples reflected light synchronously with these pulses, allowing the system to distinguish periodic infrared reflections from continuous ambient light. This temporal filtering approach maintains sensing reliability while rejecting ambient light interference.
Solution Approach 2:
The system maintains continuous monitoring capability by rapidly repeating the pulse-sampling cycle. Although individual measurements are brief, the high repetition rate ensures continuous detection coverage. This continuous periodic action maintains sensing function while the periodic nature enables ambient light rejection through temporal discrimination.
3Measurement precision
If multiple pulses are generated for error determination, then detection accuracy is improved, but activation time increases
Solution Approach 1:
The system uses rapid periodic pulsing to acquire multiple samples within a compressed time window. By increasing the pulse repetition rate and using brief pulse durations, the system can collect multiple reflected light samples quickly. This allows error determination through multiple measurements while maintaining fast overall activation response time.
Solution Approach 2:
The system rushes through the measurement process by using very brief infrared pulses and rapid sampling. Instead of prolonged continuous measurement, the system quickly acquires multiple brief samples and makes a determination. This rushing through the measurement sequence reduces total activation time while still gathering sufficient data for accurate error determination.
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, making it suitable for battery-operated devices.
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
a sensor for sensing light received via the fiber optic cable, a microcontroller coupled to the light source and for generating a voltage in response to the light sensed by the sensor
Data Source
AI summary
A system and method for automated dispensing of a fluid. The system and method includes accounting for ambient light proximate a dispensing location and generating a reference voltage in response to the ambient light. A second voltage is generating in response to a reflected signal from the location. Dispensing occurs if the difference between the reference voltage and the second voltage is greater than a predetermined amount.