Lux sensor BH1750

[Misterik]

based on script http://www.domoticz.com/wiki/Real-time_ ... _sensor... i was using the lux value to determine if it was dark enough to put on the lights. But some rooms with no windows it is earlier dark then rooms with windows, so i started with the MySensors project to build a lux sensor for each room. I finished this sensor, but i don't understand the output.

As you can see in the following picture there is a big difference between the calculated lux and the measured lux with MySensors. Does anyone know if i need to do some calculation with the output of the measured lux, or does anyone can explain this difference?

lux.jpg (84.43 KiB) Viewed 4053 times

[gohan]

Could be you got an order of magnitude wrong on the lux sensor or on the calculated value. Both values are plausible according to this table http://www.engineeringtoolbox.com/light ... d_708.html it just depends how much light was there at that time you measured

[dutchdevil83]

The calculated lux is a value based on sunlight and is always higher then a measured value from a real lux sensor. Is the mysensors lux meter in a room without windows?

[Misterik]

As you can see at the picture the measurement is taken on the same time. The measured lux value is in done in a room with windows, but with no sunlight directly into the room. I expected the calculated Lux-value to be higher but the difference is to big. I also thought about the magnitude, but if look at the values in the evening (sun almost under), its different compared to the values during the day.

lux2.jpg (35.23 KiB) Viewed 3988 times

I was wondering if perhaps more people can show(and share) the difference between the calculated lux value and the lux value of there own built BH1750-sensor-node