Illumination and Bandwidth Control Circuit for LED Optical Wireless Transmitter Driver Integrated with Passive Second-Order Equaliser for Pipe Robot Application

This paper presents the findings and illustrated results, which demonstrate a current control circuit for LEDs for optical wireless transmitters for a pipe inspection robot application. The design technique can be applied to a microcontroller to adjust the current flowing through the LED by converting it from digital to analogue. It can enable the LED light intensity to be transmitted through the robot in a pipe, retain the powerful energy of the transmitter, and adjust the optical bandwidth as needed. A digital control system control mechanism employs an analogue-to-digital converter to distribute the microcontroller's analogue voltage feedback input for configuration validation. Additionally, the circuit includes an equalizer circuit to filter the operating frequencies by connecting the lumped elements in a cascaded second-order connection. However, the proposed concept is evaluated in an experimental situation. The output voltage range of the LED driver is relatively broad, ranging from 2.65 to 3.45 V. The output current is regulated to 1,000 mA, and the results showed that the power gain of the receiver was a maximum of 2.2 mW, a maximum frequency bandwidth of 58.65 MHz, and a minimum bandwidth of 12.53 MHz at a bias current of 100 mA. The experimental results can be applied to optical communication systems in the future.