## PID Light Meter Controller

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PID control system of a light meter that measures and regulates the lighting of a lamp.

PROBLEM:
Today, photodiode is used to measure the light and it´s combined with a mathematical algorithm to reduce the error ... if we use the PID control to measure the light, then we can make infinitesimal measurements of light and this leads us to measure and see unimaginable things on the universe

SOLUTION:
Among other things, I'm proposing the invention of a sensor that doesn´t exist yet, and is similar to the one I have used (LDR), and can revolutionize many things.

APPLICATIONS: Photography, Astronomy, Architecture, and Cataract Surgery.

HOW DOES IT WORK?
a) The LDR sensor delivers an analog voltage to our port PA1, and this varies from 0 to 3 volts, depending on the light that hits the sensor. The calibration of the light in Ix, I did it by means of a light sensor. The "NXP Rapid IoT" device has a calibrated light sensor, then I turned on a lamp in front of the light sensor and the "Rapid IoT of NXP."

b) A PID controller continuously calculates an error value as the difference between a desired setpoint (SP) and a measured process variable (PV) and applies a correction based on proportional, integral, and derivative terms (denoted P, I, and D respectively), hence the name. In my case, STM32F507 board generates a PWM signal of 30 kHz, and the control data are: dt = 0.0005, Kp = 0.025 and Ki =0.025.

CONCLUSION:
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.

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