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Topic: Converting TEMT6000 value to lux (Read 1 time) previous topic - next topic

cklim85

My apology as I'm a newbie in arduino.

Can anyone please advice me how do I convert the
output of TEMT6000 into lux?

I followed the code in bildr.org guide
http://bildr.org/2011/06/temt6000_arduino/

and the output value is from 0 - 1023.

I would like to convert the readings to LUX. How do I do it?

Please advice.

johnwasser

In the datasheet you will find a chart that shows the relationship between lux and collector current.  From that chart you can calculate the formula.  Then you just need to convert the voltage measured to a current measurement.

The series resistor is 10,000 Ohms so the current should be voltage / 10000.

The voltage is: analogRead() * 5.0 / 1024.0
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cklim85


In the datasheet you will find a chart that shows the relationship between lux and collector current.  From that chart you can calculate the formula.  Then you just need to convert the voltage measured to a current measurement.

The series resistor is 10,000 Ohms so the current should be voltage / 10000.

The voltage is: analogRead() * 5.0 / 1024.0


Thank you for your advice. Based on the chart I find out that the formula is y = 1/2(x) + 0. Please correct me if I'm wrong.


johnwasser


Thank you for your advice. Based on the chart I find out that the formula is y = 1/2(x) + 0. Please correct me if I'm wrong.


I agree.  So lux = 2 * microamps.

Code: [Select]

float volts = analogRead() * 5.0 / 1024.0;
float amps = volts / 10000.0;  // across 10,000 Ohms
float microamps = amps * 1000000;
float lux = microamps * 2.0;


Or to mash it all together:
Code: [Select]

float lux = analogRead() * 0.9765625;  // 1000/1024


This should give you a value between 0 and 1000 lux.
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cklim85

Thank you for all your advices. Really appreciate it very much.

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