Go to JKU Homepage
Institute for Measurement Technology
What's that?

Institutes, schools, other departments, and programs create their own web content and menus.

To help you better navigate the site, see here where you are at the moment.

Control system for illuminance and correlated color temperature of an integrating sphere

Stephan Hromecek


As a part of a dissertation DI Andreas Winkler is developing methods for the characterization of metal surfaces based on the bidirectional reflectance distribution function. For the calibration of the used camera system, a homogeneous light source with variable illuminance and correlated color temperature (CCT) is necessary. For this purpose, an integrating sphere with two types of high-power light-emitting diodes with different CCT is used.


Figure 1: Block diagram of the multi-variable control system.

Due to the dependence of CCT on the current flow through the light-emitting diodes and the impact of warming on illuminance and CCT, a control system is required. In this bachelor thesis, a control system is designed and implemented on a microcontroller. Furthermore, a circuit for controlling the light-emitting diodes is developed, which enables to vary the current flow. For the measurement of the two quantities to be controlled, a suitable sensor is selected and integrated in the control loop.

Finally, the operation of the control system is checked by static setpoints and a sequence of step functions. Also the characteristics of the light-emitting diodes and the influence of heating are recorded.

Keywords: illuminance, CCT, multi-variable control system, integrating sphere, high-power light-emitting diodes

August 5th, 2016