Closed Loop Constant LED Light Source Using OPT101 Light Sensor and OPA569 Power OPAMP

This is a  is a precision closed-loop LED driver that provides very accurate constant light and can be used for photography, scientific research, and other applications that require an accurate light source. The project consists of light sensor OPT101 and OPA569 power OPAMP. OPT101 converts light into voltage, and OPA569 is used as an adjustable linear current source that controls the flow of current through the power LED. Installation of the Power LED and OPT101 Sensor is shown in the figure below. The overcurrent limit of LED is set to 1A using resistor R4. LM336 provides an accurate voltage reference to OPAMP which is 0.5V. The circuit works in a closed loop. At power ON, the LED light reflects to the sensor, and OPT101 provides the voltage output as the light level falls on the sensor, this voltage is fed to power op-amp, and op-amp compares the input voltage from OPT101 and reference voltage 0.5V. If there is an error, the op-amp controls the current of the LED to match the disparity between the output and input. This way light level is maintained and this is constant. It is important to have proper housing for the sensor so external/ambient light should not fall on the sensor, otherwise constant light will not be maintained.