Abstract
An extremely simple optical-sensing technique has been developed for various applications. The proposed sensing system employs one, two or more LEDs whereby each one can be used as a light emitter or light detector. The main advantages of the proposed pulse based signal conversion technique are that it leads to better spectral sensitivity; increased and adjustable resolution; reduction in cost, dimensions, power consumption and it avoids the need for expensive and precise operation amplifiers, ADCs and other external components. The sensing configuration presented here, uses only two I/O pins of standard microcontroller, one or two LEDs and is capable of detecting various optical effects. Using multi-configurable I/O pins the LED used as a light detector is reverse biased so that the photocurrent generated by the incident light discharges its inherent capacitance throughout Hi-Z input impedance. A simple timer circuit that measures the decay-time taken for the discharge process from logic 1 to logic 0 provides direct digital output proportional to the light intensity. This sensing concept has been tested in many applications and some of them are described here.
Original language | English |
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Pages (from-to) | 1-6 |
Number of pages | 6 |
Journal | Journal of Physics: Conference Series |
Volume | 76 |
Issue number | Conference 1 |
DOIs | |
Publication status | Published - Sept 2007 |
Keywords
- light emitting devices
- imaging detectors and sensors
- pulse digital circuits
- photodetectors
- sensors
- amplifiers
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Instrumentation
- Electrical and Electronic Engineering