Study of simple spectrophotometer design using LDR sensors based on arduino uno microcontroller

A spectrophotometer is an apparatus that can be used to identify the constituent elements of a material. Spectrophotometer uses the principle of interaction between the light spectrum that has a certain frequency with the material so that it can be measured the transmittance or absorbance of the sample as a function of concentration. The purpose of this research is to design a simple spectrophotometer using LDR sensor to convert the scale of light intensity into an electric scale, 28BYJ stepper motor and ULN 2003 driver motor controlled by Arduino Uno microcontroller for light spectrum selection, Op-Amp system as a signal amplifier and LCD 20x4 to display the output intensity value. The test results on Copper (II) Sulfate or CuSO4.5H2O samples with the concentration of 0.15 M, 0.25 M, 0.4 M, 0.5 M, 0.7 M and 1 M gave the absorbance value of 0.12, 0.32, 0.51, 0.66, 0.79, and 1.07 respectively in the red spectrum. The other solutions used to test the spectrophotometer system are two types of food dye solutions. This study provides a linear relationship between absorbance and concentration.