Resistance In LED's

[QSQCaito]

Ok ok,im about to build a wah, and the rocker pedal would be remote, so i'm going to use the well know idea of the led+ldr.
The question was: How many resistance does a LED needs in order for it to be "dimmed enough" for the ldr to read it's max resistance, that in my case will be of 100k.
The LDR im about to use is a 1.3k-100k, i think this range will be enough.. no wah uses its full sweep right?
As i can get those slide pots, i need no rack, nor pinion. But the values of the slide pots i can get are:(if not wrong) 5k-10k-25k-50k-100k..

if 10k are enough for a led to be off(or for the ldr to read 100k) I would use the 5k pot.. because if we start with 4k7, +5k this would give a close value..

hope you get my "idea"

thanks in advanced

bye bye

DAC

[Seljer]

Well it depends on the model of the LDR and the type of LED you're using. As LDRs respond to different colors of light differently and LEDs come in different colors with different magnitudes of brightness.

Take a pot (about 50k) a small resistor (like 470ohm, just so you don't accidently turn down the pot and burn out the LED) and wire them to the LED, which is allready coupled to the LDR, the with your multimeter measure the resistance of the LDR and see how much range you need.

[Ge_Whiz]

Also will depend a lot on how well they are coupled together. This is one thing you will have to determine yourself.

[QSQCaito]

So i'll buy the ldr, shrink it with a led.. and just test.. then buy the pot needed, right??

The color of the led, i think it will be green because it's CdS... i don't remember, gotat check the article.

Thanks  a lot

bye bye

DAC

[QSQCaito]

Didn't want to create a new thread..

So here i have a question, lets first take alook at this picture.


Once i have all this done, it will be time to calibrate. I grab my DMM, where should i measure resistance to be 0, and 100k, while i change the sweep of my pot??

thanks a lot

bye bye

dac

[Seljer]

I think a LDR that goes higher than 100kohms would be necessary. One that goes from about 5k->1M would work better

(though I'm pretty sure you could get away with the 1.3k-100k LDR you have if you use a 10k resistor instead of the 100k resistor)


as for the multimeter: measure across the the 2 terminals of the LDR part.

[QSQCaito]

I think a LDR that goes higher than 100kohms would be necessary. One that goes from about 5k->1M would work better

Why is it these?? do you know?

you have if you use a 10k resistor instead of the 100k resistor

What's the use of that resistor??

Thanks a lot!

bye bye

dac

[QSQCaito]

Forgot to add.. i can get an ldr that goes from 400ohms to 1meg. If it's better, and it have been tested, i can buy that without any trouble.. i should use a 100k pot with it??

thanks a lot

bye bye

dac

Edit: PS: I could get other LDR values, all from almost 0 to 500k 600k 250k 300k 10meg

[QSQCaito]

One more question

Have you built this seljer??

I would appreciate much a starting point, to know that this worked using "X" ldr and "X" pot..

thanks a lot

bye bye

DAC