It's not specified, likely because typically LDR response time is abysmal...and hence potentially something that the manufacturers don't want to sort, spec, and publish (= guarantee) min/typical/max for. That would also raise the cost of the component...and we're back to packaged optocouplers.Seiche wrote:^good idea but is response time actually something that is specified when buying LDRs? I know musikding doesn't (they only give the light and darkness resistance).
It's pretty common with the more expensive optocouplers to see those specs...which is, after all, the component that an LDR+LED is trying to make sub for, but done cheaper. Or maybe in some selected cases preffered over for spec reasons, not just price...
There is of course limitations to what we can find out...but starting with max dark and min bright resistance is #1...narrows it down...then to make the 'it responds pretty quickly' less subjective and slightly more measurable (feed it a 3v peak signal, then cut it, see how fast it takes for a (slow?) DMM to go from reading that min bright to max dark resistance after 1 second, 5 seconds, 10 seconds....is a help. Look at the Vactrol / perkins-elmer pdf datasheets to see what kind of things they spec for. In an ideal world, it would be cool to do the same exact test with whatever optocoupler one might have on hand with those particular specs published, functioning in the same (clone) circuit, as a comparative, to reduce the DMM's impact or skew of such measurements.
Probably few other people care about this, but as I've said elsewhere, the optical specs have exponentially more impact on the resulting sound of this kind of circuit than probably any other section of the circuit.