Compact Liquid Sensor with LED Array and Wireless Energy Harvesting
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Solution Overview
Problem
Current devices for measuring the absorption spectrum of liquids, particularly in water quality assessment, are often bulky, power-intensive, and costly, making them unsuitable for compact and continuous monitoring in various locations.
Innovation Solution
A compact sensing device utilizing a light emitting diode (LED) array, a reflector, and photodetectors to measure light intensity, combined with a control circuit and temperature sensor, which can estimate absorption spectra and harness motion energy from flowing liquids for partial power supply via wireless power transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a spectrometer is used to measure absorption spectrum of liquid, then measurement precision is improved, but device complexity and size increase
Solution Approach 1:
The spectrometer is divided into separate components: a compact sensing unit with LED array and photodetectors for light measurement, and a remote computing device for spectral analysis. This segmentation allows the measurement function to be performed locally with minimal hardware while complex data processing occurs remotely, reducing on-site device complexity.
Solution Approach 2:
A light guide acts as an intermediary to transmit light between the sensing unit and the remote spectrometer/computing device. This allows the separation of light collection functions from complex spectral processing, enabling compact sensor design while maintaining measurement precision through remote analysis.
2Measurement precision
If a spectrometer is used to measure absorption spectrum of liquid, then measurement precision is improved, but the device size increases making it unsuitable for immersion in water pipes
Solution Approach 1:
The system is segmented into a small immersion-compatible sensing unit and a remote computing device. The sensing unit contains only essential components (LED array, photodetectors, minimal optics) that fit within water pipes, while the bulk of the system resides remotely where space is not constrained.
Solution Approach 2:
The system transitions from a single integrated unit to a distributed architecture where the sensing unit operates in three-dimensional space within the pipe, while data processing occurs in a different spatial dimension (remote location), effectively removing volume constraints from the critical measurement component.
3Measurement precision
If conventional measurement devices are used, then measurement capability is achieved, but power consumption is high
Solution Approach 1:
The LED array operates in periodic pulse mode rather than continuous operation, with each LED sequentially activated for brief measurement intervals. This periodic operation dramatically reduces average power consumption while maintaining measurement capability through time-multiplexed spectral acquisition.
Solution Approach 2:
The system replaces traditional continuous-spectrum light sources and mechanical scanning monochromators with electronic LED arrays and digital signal processing. This substitution eliminates power-intensive components while achieving equivalent or superior measurement precision through photodetector arrays and computational spectroscopy.
4Measurement precision
If materials for conventional devices are used, then measurement function is achieved, but material cost increases
Solution Approach 1:
The system uses inexpensive, commercially available components including standard LED arrays, simple photodetectors, and common optical materials for the sensing unit. These low-cost components are replaced or recalibrated as needed, eliminating the need for expensive precision optics and reducing overall material cost while maintaining functional precision.
Solution Approach 2:
The system changes the spectral measurement approach from using expensive broadband continuous-spectrum sources with mechanical monochromators to using multiple discrete-wavelength LED sources. This parameter change in the light source characteristics enables the use of cheaper materials while achieving the same spectral information through wavelength-multiplexed measurements.
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 device achieves a compact, cost-effective, and power-efficient means to continuously monitor liquid absorption spectra, suitable for diverse locations, including water pipes, with reduced material costs and minimal maintenance.
Implementation Method 1
The sensing unit comprises a light emitting diode (LED) array for emitting light. The LED array comprises plural LEDs. Each of the LEDs is configured to generate a shower of light having an emission spectrum having a single dominant spectral peak at a peak wavelength.
Implementation Method 2
The reflector is shaped to be substantially similar to one half of an ellipsoid except on the opening. The LED array is located at the first focus so that the emitted light incident on the reflector is reflected to the second focus, causing the emitted light after reflection to be refocused at the second focus.
Implementation Method 3
A first photodetector (PD) located at the second focus is used for measuring an intensity of the refocused emitted light to thereby yield a reference intensity. A second PD is used for measuring an intensity of the probe light beam received after the probe light beam passes through the liquid
Implementation Method 4
The sealer is further prepared to have a convex surface on the opening. The convex surface is shaped to refract the emitted light incident on the opening to form the probe light beam. In addition, the convex surface is shaped such that the probe light beam is substantially collimated when the device is immersed in the liquid.
Implementation Method 5
The quality of drinking water can be assessed by measuring an absorption spectrum of a water sample that may be contaminated by organic contaminants such as toluene. It is known in the art that ultraviolet-visible (UV-vis) and near infrared (NIR) spectroscopic methods are useful to detect such organic contaminants.
Data Source
AI summary
A compact device useful for measuring an absorption spectrum of a liquid, such as water with organic contaminants, is provided. The device comprises an array of light emitting diodes (LEDs) each emitting light with a unique spectral peak. A reflector shaped as a half ellipsoid reflects the emitted light to form a reference beam. The reflector has an opening to allow part of the emitted light to form a measurement beam after passing through the liquid. Two photodetectors measure the reference beam and the measurement beam to give a reference intensity and a measured intensity, respectively. The LEDs sequentially emit showers of light one-by-one, giving plural pairs of reference and measured intensities for estimating the absorption spectrum. The device receives energy from a separate power-providing device through wireless power transfer. The power-providing device harvests motional energy of the flowing liquid to generate electrical energy.