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White-Blue Screening

In order to study the capability of the cultures to absorb energy coming from light sources depending on their coloring. The variable in which this capability is measured is the temperature that the cultures reach compared with others. These temperatures are measured by a system of thermocouples. For this objective, it has been designed a dish in which our E. Coli and yeast cultures are studied. There are as well two reference cultures: one entirely black and another totally white. The cultures are exposed to light exposition coming from the sun. All cultures are previously kept in constant and known temperature. In order to make sure that the temperature differences among the cultures are due only to albedo effect, two strategies have been designed.

1. Several light sensors have been laid out symmetrically. The signal received by these sensors is transmitted to an electronic circuit which produces an electric response that finally ends up in the datalogger.
2. Several thermocouples are arranged surrounding the cultures to make sure that the external temperatures are equal for all of them. It has been used a recording system quite similar to the Red Hose one.

Therefore, any temperature difference between the cultures has to be produced by the capability of absorbing light. This temperature is then measured by another thermocouple inserted into the culture. Furthermore, all this data is recorded and shown in real time through a computer screen.

Light sensor

With this electronic circuit we aim to adecuate the signal coming from the light sensors (photodiodes)

Con este circuito se pretende realizar la adecuación de la señal proveniente de los sensores de luz (los fotodiodos), para poder obtener unas señal de mayor amplitud y proporcional a la luz radiante de forma que se facilite la adquisición e interpretación de esta en tiempo real.

La señal generada por un fotodiodo se puede comportar de dos formas distintas dependiendo la configuración en la que se conecte: En modo fotoconductivo y modo fotovoltaico, este último caso no nos interesa, ya que se utiliza para la obtención de energía eléctrica, sin embargo el primer modo permite obtener una relación más precisa y estable de la interacción que se produce entre la energía de los fotones y el desplazamiento de electrones que éstos generan al incidir la luz sobre la superficie fotoactiva del fotodetector. El circuito equivalente de un fotodiodo viene definido por el siguiente diagrama y curva característica: