Well, I was not going to post anymore to avoid
breaking rules but this needs to be cleared up. Chris, your definitions
are simply wrong. Please see this definition of a Photocell also known
as an LDR (light dependent resistor).
https://en.wikipedia.org/wiki/Photoresistor The device (an
LDR) is not a 4 legged device with integral LED. That is an optocoupler.
It is a "light dependent resistor", 2 legs, pretty straight forward.
The definition is clear as is the description.....LDR means "light
dependent resistor"...it does NOT mean LDR encapsulated with an LED.
That is a 4 legged device and by definition is NOT an LDR but may
contain one (or something else). Here is an optocoupler as described by
the manufacturer,,,,
http://www.newark.com/advanced-photo...00v/dp/71C0279
As you can see An LDR is one thing and an optocoupler is a different
thing by both definition and operation. While they both use light to
vary the resistance the two do have definitions as to what they are.
Also, there is no requirement the light source be an LED in the case of
an LDR. Optocouplers in audio have "problems" but it's not my job to
explain them or even care about them. I only care that folks understand
the proper terms. LDR...2 legged device...."light dependent
resistor"......4 legged device containing LED and LDR is an
optocoupler.....by definition from the manufacturer.. "The NSL-32SR2 is
an O/P
Resistive Optocoupler, consists of an LED
input optically coupled to a photocell".
Ed