Characterization of “cool” and “warm” white light-emitting diodes for low-cost spectrophotometry

Abstract

The emission properties of “cool” and “warm” white light-emitting diodes were studied in the context of low-cost spectrophotometry. The suitability of pulse-width modulation as a method to control the diode brightness was examined. Both types of light-emitting diode demonstrated emission standard deviation minima at a pulse-width modulation frequency greater than 2000 Hz. The functional wavelength ranges of the light-emitting diodes were approximated using the linearity of brightness as a function of pulse-width modulation duty-cycle and the root mean squared deviation from mean for absorbance measurements. Both light emitting diode types demonstrated good stability in absorbance measurements over long operation times. The “warm” light emitting diode demonstrated a broader range of wavelengths useful for spectrophotometry.