Roll your own ldrs for nautilus

[euphyllia]

Could anyone help advise me how to properly measure photocell resistance to make my ldrs for nautilus and the like?  I bought some GL5549 photocell (100K-10M) and when I test dark resistance it varies wildly. Often the dark resistance will go off the scale even when my multimeter is set to 200M. Are these photocells ok for Nautilus?

[midwayfair]

You can put a 10M in parallel to see if that helps measure them.

I'd be more concerned about the switching speed and light resistance if your dark resistance is reliably above a couple M. 100K is rather high for this circuit; you want something closer to 10-30K on resistance in-circuit, and fast switching. It doesn't mean they won't work, but you might not get some of the crazy sounds.

[euphyllia]

Thanks for the advice.  Datasheet states 20ms increase and 30ms decrease time.  I'll retest light resistance too.  Oh,  and I think I'll order some vactrols.  I was hoping to avoid the expense,  but I may need to in order to get an accurate effect.

[midwayfair]

Thanks for the advice.  Datasheet states 20ms increase and 30ms decrease time.  I'll retest light resistance too.  Oh,  and I think I'll order some vactrols.  I was hoping to avoid the expense,  but I may need to in order to get an accurate effect.

If it helps, the Silonex 7532 will work fine (they're extremely versatile, too), as well as Smallbear's 9203 photocell. They're not AS good as the VTL5C3 or Smallbear's clone, but they're also a fraction of the price. Of course, if your light resistance tests low enough, the ones you have are also good.