How to make a lumen meter?

[baileychic]

How to make a lumen meter?

I am planning to make a lumen meter to measure lumen output of Power LEDs using PIC12F microcontroller.

Lumens are expressed in Lumens/Watt usually.

So, if I know the voltage acorss the Led and current through it then I can calculate LED power. If datasheet of LED gives Watts per lumen information then can I convert my calculated watts into Lumens?

If the LED datasheet doesn't have the information about Watt/Lumen or Lumen/Watt then how can I find out Lumen per Watt by only measuring LED voltage an dcurrent without using any sensor?

 

[betwixt]

Firstly, you cannot calculate the light output purely on the DC input power to an LED. The missing factor is its efficiency which varies greatly across products and design purpose.

There are other factors to take into account - the spectral response (the output at different wavelengths), the radiation angles (the output in different directions) and whether these vary under different drive conditions. If you just want a 'general' idea of brightness, for example to match LEDs of the same type you can use a CdS LDR which has a fairly broad spectral response and poor directivity. Just measure its resistance at a fixed distance and angle from the LED. If you need a more scientific measurement, first narrow down the viewing angle and be prepared to take many measurements from different angles and do it through a calibrated sensor, using filters if necessary.

It is quite a complicated task to derive a single figure result!

Brian.

 

[paulfjujo]

Hello,


and with t a TLS325 LIGHT-TO-FREQUENCY CONVERTER
frequency output f (light)
**broken link removed**

 

[schmitt trigger]

AMS has a family of I2C enabled light sensors.


https://ams.com/ambient-light-sensors