Light Meter. How to Make an Proper Readout?

Thread Starter

MCU88

Joined Mar 12, 2015
359
Hello...

I have made an project that has an LDR and ten LEDs that respond accordingly to the level of light that the LDR sees. Q: How do I add some numbers, a scale to the LEDs so that they have an meaningful readout?




 

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DickCappels

Joined Aug 21, 2008
5,759
If you want to make something calibrated and that works with different light sources you would need a filter or set of filters to correct the response of the LDR to have a photopic response. This is approximately the same response as the "green" receptors in our eyes. An expensive solution.


https://en.wikipedia.org/wiki/Photopic_vision

If you consistently use it with the same kind or light (for example, same color temperature florescent or incandescent) then you can simply place a diffuser over the LDR (a ping pong ball cut in half works nicely) and then put it on the desk side-by-side with a borrowed illuminance meter (sometimes called a "Lux meter"), which is calibrated in Lux (for the originator of the until, Harrold Luxemberg) and calibrate your instrument for different amounts of incident light.
 

Thread Starter

MCU88

Joined Mar 12, 2015
359
Sweet. So ...

a. Ping pong ball cut in half
b. Readout in Lux
c. Calibrate to meter

Cheers!
 
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