This project can be applied in Astronomy / Photography, and has the goal of developing a system with which we can measure and control the amount of lighting that a star or a galaxy emits using PID controller. For our best study, I have used a lamp to simulate a star and divided this project into the following sections: 1) Software Installation; 2) Light monitoring and calibration; 3) PID Controller; 4) Tests; and 5) Conclusions.

A light meter is a device used to measure the amount of light. In photography, a light meter is often used to determine the proper exposure for a photograph. Typically a light meter will include either digital or analog electronic circuit, which allows the photographer to determine which shutter speed and f-number should be selected for an optimum exposure, given a certain lighting situation and film speed. Meter calibration establishes the relationship between subject lighting and recommended camera settings. The calibration of photographic light meters is covered by: ISO 2720:1974 and ISO2721:2013.

The lux (symbol: lx) is the SI derived unit of illuminance and luminous emittance, measuring luminous flux per unit area. It´s equal to one lumen per square meter. One lux is equal to one lumen per square meter: 1 lx = 1 lm/m2 = 1 cd·sr/m2.

Light meters or light detectors are also used in illumination. Their purpose is to measure the illumination level in the interior and to switch off or reduce the output level of luminaires. This can greatly reduce the energy burden of the building by significantly increasing the efficiency of its lighting system. It is therefore recommended to use light meters in lighting systems, especially in rooms where one cannot expect users to pay attention to manually switching off the lights. Examples include hallways, stairs, and big halls.

This system proved to be very practical to make use of our "STM32F407" board. Now we understand clearly the concepts of luminescence. It is also clear to us the applications of lighting in professional works to determine more precisely if there is more or less light in a room or concert hall for example. In reality, individual eyes vary slightly in their luminosity functions. However, photometric units are precisely defined and precisely measurable.

Although we had difficulty using the LDR sensor as a light meter, we already have experience and learned the calibration procedure that can be useful in case we use another type of light sensor. The PID control system worked well and surely we will use it in other versions that we will analyze. This is the way forward to improve this system or make a second version in the future.

PUBLICATION:
https://www.hackster.io/guillengap/pid-light-meter-controller-724672
https://github.com/guillengap/pid-lightmeter-adacore