LDR/LED question...

[gak]

hey, a Light Dependant Resistor is a variable resistor that changes it's value depending on how the light affects on it... right?
and a pot is also a variable resistor... so, my question is.. to replace a pot with a LDR on every circuit can be done just simply putting a LDR instead of the pot and adding a LED to the circuit, right?

i'm intrested about it, cause if it's possible and that simple it would made a lot easier the construction of a expression pedal than using pots and developing a mechanism to move them...

[zener]

Actually, if you use the search function above, you'll find a lot of stuff regarding LED/LDR combo for it has been discussed a lot before.

[gak]

thanks, i've been looking on other threads..
i've found morley little alligator schematic (http://www.morleypedals.com/plaes.pdf) and it seems to be a pretty simple project.. i just have a couple of questions...
at first... how L1, L3 and LDR1 should be mounted..
second.. what's L4 function? it's the on/off LED indicator or is something related to the optical effect system?

[zener]

If you look at the schem, yeah no brainer at all. But what's difficult is the pedal mechanism. How are you going to make the light the LDR receives go dim and bright as you move foot rocker. You have to make it "smooth" otherwise, you'll end up with much of the effect happening only near the end of the foot rocker's motion or near the tilt up.

I built a Morley wah along with a foot pedal. What I did is I mounted the LED on the "ceiling" of the rocker while the LDR is mounted upright in the base or the (floor) of the pedal. There is a small plastic plane, an inch or less from the LDR, that covers it. This plastic is "floating", being hung horizontally by two rubber on each side of the pedal and a string which is actually a part of pulley system. The string is attached to the heel of the foot rocker.

So here is what happen: When you start to depress the foot rocker, the LED is being lowered closer to the place of the LDR. Simultaneuosly, the string is being pulled by the upward movement of the heel. With that, the "gate" gradually opens as the LED goes closer to the LDR. How fast the gate opens and the LEd goes closer to the LDR depends on how fast you depress the foot rocker.

Sounds clever, right? But actually, like what I previously said, the effect is only happening near the end. I dunno, I might be stupid for what I did but I'll have to think of something else to actuate the LED/LDR smoothly. Otherwise, I'll just use a slide pot.

Regarding your question, I think LDR1 will have two LEDs as per schem. The L3, along with L2, sets the min vol while the L1 adds light to what is being given by the L3 to the LDR to actuate the effect. L4 is indicator.

Breadboard it first and find it out yourself. I might be wrong. Btw, is there a LDR that works: more light = more resistance? The opposite is what I know (and what I have). The whloe thing might be reversed just in case.

[black mariah]

The Morley Chorus/Flanger that I have has a piece of fabric in front of the LDR. When you push the pedal down, the end that's attached to the back of the pedal lifts up, exposing the LDR to the light that's mounted in the back of the pedal. I'll take a couple of pics if anyone needs them. The inside of that thing is quite frightening though. :lol:

[zener]

Sure, mariah. I would love to see the guts of a Morley. I might get something from it for me to mod my existing Morley wah. Thanks

[gak]

thanks for the explanation.. i think i'll try to build it
another quistion... i've never worked with LDRs... there're different values like on normal resistors o what..?