Electronic Project : AVR Lux Meter

The illumination is how the level of flows of light falling on a surface. The flow of light is visible, which is defined in the flow (the light power) divided by relative sensitivity of the naked eye on the visible spectrum. This means that the Lux is well suited to the light level of meaning to the human eye. To measure the lighting, we can use Lux Meter.
We can build ourselves Lux meter using electronic components. At the detection of light we use photo diode. However, there is a difference between the spectra simple answer photo diode silicon and the naked eye, it can not be used for lux meter. Some photo diodes for lighting have a sensor compensation color filter on the window to correct its response spectra.
In this project, Photo-diode current results light that is well proportional to the light input power when used in short fashion. In this lux meters, the output current is converted into a voltage converter with an IV, he is caught by a micrcontroller AVR and displayed in terms of lux. The ppamp U1 in the circuit diagram that acts IV conversion circuit and its conversion becomes 50mV / μ A, in accordance with a record of comments R5. The capacitor C5 is to obtain the correction, it cancels Ct of the photo diode (about 200 pF). In this case, greater capacity in May rather be 220 pF because the high frequency signal is not necessary. The lux meter is powered by a 9V battery.

Download schematic, document, firmware (zip) here
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