Potentiometer a simple light dependent resistor-based digital

A digital potentiometer, which can be used to implement automatic calibration procedure in a circuit, to control a switch of a power supply, or as a load tester, was developed by using a light-dependent resistor (LDR) and implementing a proportional controller. It consisted of a light emitting diode (LED) used to change the resistance of LDR, two LDRs set as the output and the feedback of the controller, a keypad to enter the set point, an LCD to present the data and the processes of microcontroller, and an ATmega 8535 microcontroller to manage all processes of the system. Under the trial-error tuning method, it has been obtained that the proportional constant was 500. For the desired resistance ranging from 5 to 10kΩ, its steady-state error was in the range of 20 to 290Ω. In fact, this maximum steady-state error (290Ω) was higher than those obtained from the previous works. However, the developed system was simple and low cost.