led/photoresistor based blend instead of a pot. Pros cons please.

[oram]

hello folks. I'm tring to blend an oscilator (schmidt trigger, sq wave) into a pre amp circuit. I'm waiting on parts to make the buff and blend circuit, i'm assuming this will be best. But in the mean time as i love led/photoresistor combo's i thought i'd see if this could work as a blender. The few and very prevalent problems i've ran into, is that the photoresistor never fuller quietens the signal however quiet, even with a pull down resistor it's never fully off. Is this because photoresistors aren't suitable for this job?

Also i'm trying to find a better way of dimming the led with voltage, it seems to draw to much voltage from the circuit and changes the pitch of the squarewave with it. I simply ran the + into a 100k pot, into the led then to ground with a 1k pull down resistor off the led.

cheers... i'm kinda new to all this so apologies for any misunderstanding here...

ta

dazz

[tubegeek]

An LDR can be analyzed easiest (at first) as two resistors: one that shows up when the lights are out and one that takes its place when brightness hits it.

There is a wide range of values in real LDRs between these two extremes, each LDR will have a max and min resistance associated with it.

At no time will it ever be infinity for max, nor zero for min. So when used as part of a resistive voltage divider, an LDR can never short out a signal to zero level, the way, say, a piece of wire or a switch or a potentiometer can.

[oram]

Thankyou. Just not suitable for the job. cheers tubegeek

[oram]

and this solved my led "explosive" mistake...http://www.seekic.com/blog/project_solutions/2011/08/22/30_mA_LED_Dimmer.html 

[cloudscapes]

another con for LDRs is the min/max range values between same-brand same-model LDRs can vary. sometimes enormously.

[oram]

cloudscapes: I guess this means my plan for controlling the pitch of an oscillator (for drone purposes) via an envelope LED will yield inconsistent results then? Will it be noticeable, as i plan on making a contact mic mixer with all kinds of noisy circuits mixed into it and triggered by the envelope LED on each track. Would be helpful for it to be consistent.

thankyou