DFR0026, light sensor module

userHead Jose 2013-07-17 10:31:03 6681 Views3 Replies
This is from the shout box, An interesting question about the technical details of this module.
wenfangsong: hi, who can tell me the unit of data returned by ambient light sensor DFR0026?thx

Jose: Wenfangsong, the unit is volts, it measures light resistance. [link]

wenfangsong: Thanks very much, Jose. I see there says "Dark has a low value", but i find the return data decreases as the ambient light increases. Could you offer me some explanations about this? Is there any relation between the volts and the intensity of ambient light? i.e., how can i know the light intensity in lux according to the data in vlots from DFR0026?

Anyone knows the answer to this?
2013-08-07 15:50:10 Hi, wenfangsong
LDR is a type of semiconductor and its conductivity changes with proportional change in the intensity of light.
It means the resistance value will change with the light.The light is higher, the value is lower.And in a similar way, the lower, the higher.

the theory: ... ion_of_LDR
And you know. It is a non linear it is not easy to read the lux ,except you have a non linear relationship table. ... istor.aspx
I hope I can help you
userHeadPic Grey.CC
2013-08-07 14:23:54 [quote author=wenfangsong]
I found that the read value is lower when the ambient light intensity is higher. When it is dark, the data is more than 1000. I also have the doubt about the unit and how to translate it to lux. Do you have any results about this? Very appreciate if you can give me a reply.
userHeadPic Jose
2013-07-17 10:54:02 The light sensor is a LDR and it will change it's resistance to high when it's dark and to low when it's bright.
This results in a change of the voltage which is coming from the sensor.

Regarding to Ohm's law the voltage drop across the resistor increases when the resistance increases.

The light sensor attached to The Arduino analog pin A0 will give you exactly that values. In a range from 0 to 5V it will show 5V when it's dark and 0V when it's under full light. So the output is kind of reversed but with a mapping easy to convert in a non reverted value.

To measure the LUX with that particular sensor will give you also reversed readings due the circuit used on the board. As a quick solution you could use a LDR alone and connect it with 5V and Analog pin A0 and then a pull resistor from A0 to GND. Then load the sketch you find here: ... #msg277211 This will give you LUX readings in the right order. With that data you could calibrate the sensor and map it's readings to the right order.
userHeadPic lumi