ldr/optoisolator

[scaesic]

i want an optoisolator with an ldr that will sweep from 1k to 10M variation from light to dark a corresponding led.

anyone know where i can find datasheets to find such a component?

[chunks717]

its hard to find one with that much range, but a few in series looking at the same (or parallel) led(s) might get you close, but it probably woln't do the whole travel terribly fast.....there is a 100 pack of ldrs from jim-pac (jim-pak?) that is sold through digi-key (or was at least)
that have a few in each pack that do low k-range to 3/4/5M range....................

my guess is that you may do better with a control voltage, especially if you want fast travel.

what is your intended use?

[scaesic]

the intended use is to have the ldr wired in parralel over a pot, and have the led variation sweep effect parameters up and down. With an ldr with a big range such as that, you'd be able to pretty much vary a pot fully up and down, assuming pots are valued between 50k-500k ish, which they mostly are.

[Dave_B]

The VTL5C3 is rated to 10meg.  Depending on what you're feeding it, you may need to put a 1k in series for the low end.

[QSQCaito]

CLM8200  LED + LDR - AXIAL  - 220 - 2.8KΩ-10MΩ


Hope it helps then you could probably help me

Bye bye

DAC

[chunks717]

right...ummm optoisolator = vactrol.
not NECISARRILY something I rolled from whats on the bench.......

I guess the man did say datasheet................
I'm going back to bed.

[Torchy]

Ok, I keep seeing posts that want vactrols etc that go from low ohms to 10Mohms. Heres a question.

Given the way vactrols etc are used in fx pedals, what is more imortant - range or reaction time. Say Im building a trem lune. The schem/BOM cals for a specific vactrol. Once the dark resistance gets above 1Mohm how does the extra resistance affect the circuit response, and given its a trem wouldnt the follower action (ie how quickly the cds/ldr reacts to the changing LED intensity) be more important than the resistance range ?

Ive built several opto-trems/easyvibes etc and Ive found that the dark resistance above 1Mohm is pretty inconsequential. I get crap results from fast reacting LDRs on vibes and good results from slow reacting ldrs on trems etc.

Or am I reading this all wrong ?

[RedHouse]

i want an optoisolator with an ldr that will sweep from 1k to 10M variation from light to dark a corresponding led.

anyone know where i can find datasheets to find such a component?

Did you try Mouser, DigiKey, Allied, and BG Micro? ...etc... ad infinitum, ad nausium.

[Paul Perry (Frostwave)]

Given the way vactrols etc are used in fx pedals, what is more imortant - range or reaction time. ....Ive built several opto-trems/easyvibes etc and Ive found that the dark resistance above 1Mohm is pretty inconsequential. I get crap results from fast reacting LDRs on vibes and good results from slow reacting ldrs on trems etc.

Whether you need a LDR that goes above 1M depends on the circuit, not usually needed , as you found.
The effect of LDR speed in a LFO control, depends on the kind of LFO you are driving hte led by. Because, if you have a square wave LFO & just have the LED flashing on & off, it might be too choppy, or give you clicks.. while a slower LDR would smooth out the resistance change.

[scaesic]

i think this is probably an area for experimentation, thanks for some pointers though.

[slacker]

In my experience of LFOs that use a LED/ldr combo the Led quite often doesn't ever go completely off so the dark resistance probably isn't that important. In some circuits the minimum resistance isn't that important either, so long as the LDR changes resistance enough to do what the circuit needs thats all that matters.