The paper presents a color sensor system that can process light reflected from a surface and produce a digital output representing the color of the surface. The end-user interface circuit requires only a 3-bit pseudo flash analog-to-digital converter (ADC) in place of the conventional/typical design comprising ADC, digital signal processor and memory. For scalability and compactness, the ADC was designed such that only two comparators were required regardless of the number of color/wavelength to be identified. The complete system design has been implemented in hardware (bread board) and fully characterized. The ADC achieved less than 0.1 LSB for both INL and DNL. The experimental results also demonstrate that the color sensor system is working as intended at 20 kHz while maintaining greater than 2.5 ENOB by the ADC. This work proved the design concept and the system will be realized with integrated circuit technology in future to improve its operating frequency.
Abstract:A new design of a color sensor circuit that can differentiate four colors and produce digital outputs is presented in this paper. The proposed circuit uses a photodiode as a light transducer and few additional electronic components. The advantage of the proposed architecture is that the number of required components is fixed regardless of the number of detected colors with only increasing the number of component inputs. This feature is important especially in element count and low power consumption. The sensor circuit is implemented on a breadboard with commercially available off-the-shelf electronic components. The objective of this work is to validate a new architecture of color sensor circuit design using simulation and experimental analysis as a proof of concept for a future implementation as integrated circuit.
In this paper, a CMOS interface circuit as part of an optical sensor-based microsystem for pH monitoring applications is presented. The proposed circuit is capable of processing a voltage signal produced by the light transducer and generating 8-bit digital outputs representing the color information (i.e. wavelength). A resolution of 8 different colors has been achieved as a proof of concept and can easily be extended to a higher number of colors without a major modification in the architecture. The proposed interface circuit is a mixed-signal solution that consists of analog as well as digital building blocks along with a light transducer. It can be used as a portable and non-intrusive optical sensor for biomedical and environmental sensing applications.
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