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Simplified Lux for Embedded and Micro Controllers

From Texas Advanced Optoelectronic Solutions, Inc. / TAOS
 

 

The TSL2550 is designed for use with broad wavelength light sources and uses two photodiodes for deriving illuminance (i.e. lux). The first photodiode (Channel 0) is sensitive to both visible and infrared light, while the second photodiode (Channel 1) is sensitive primarily to infrared light. Channel 1's digital output is used to compensate for the effect of the infrared light component on Channel 0. The formula below derives the ambient light brightness from the digital outputs of both channels to approximate the human eye response.

If an embedded or micro controller is used to control the TSL2550 device, equation (1) may be difficult to implement since floating point arithmetic operations are generally not supported. Consequently, an alternative method using a simple look-up-table (LUT) was investigated to provide a simplified lux calculation.

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