photodetector

[aspoojak]

hey, i ve been working on the photodetection property of LDR.
i need to know which one of the 3 photodetectors s better for the detection of red light. right now i'm using an LDR. i need to convert the output to frequency. how do i do it?? or is it better tht i use a phototransistor and use v-f converter.

 

[MikeMl]

Break it down to three questions:

What detector is sensitive to red light?

How do I make a circuit so the detector makes a voltage proportional to illumination?

How do I convert voltage to frequency?

 

[fernando_g]

CdS cells (photoresistors) have a peak sensitivity at the green wavelength, but are quite useable to detect red light.

Silicon photodectors (photdiodes or transistors) have a peak sensitivity at the infrared wavelengths, but are alse quite useable at red.

So your first order of businnes is to get a good optical red filter to place in front of your detector.

Now, if you want to go the easy route, Avago Techonologies has a broad range of light sensors with the output properly conditioned:

Avago's Ambient Light Sensors

 

[aspoojak]

hey fernando_g
i understand the importance of optical filters.i need help on selecting the detector. or is it better if i use a light to freq converter?

 

[fernando_g]

I found something better, it already has the RGB filters built in, and also provides an output frequency.



See the AXE045 color sensor