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photodetector

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aspoojak

New Member
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

Well-Known Member
Most Helpful Member
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?
 
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fernando_g

New Member
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

New Member
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

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

PICAXE

See the AXE045 color sensor
 
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