Wouldn't a PV opto's output look like a forward-biased diode when it's turned off? It would seem to me that they should turn ON slowly but OFF quickly because once the input drive is gone, the output is just a diode, connected from gate to source of the FET you are driving. On Fri, Jun 14, 2013 at 2:51 PM, Denny Esterline wrot= e: > It's been a while since I did the design, but if memory serves, the bigge= r > difference between the TLP190 and TLP191 was the presence of an internal > pull down resistor on one of them. Thus one needs an external resistor an= d > the other does not. Fuzzy memory seems to suggest that the current > difference was naught once you added the external resistor. Bear in mind > that since the turn off time is controlled by that pull down resistor, > your're never going to get very fast switching with a PV opto. Plenty fas= t > for 60 Hz mains work, but you need to plan for a considerably longer time > in the linear region while switching. > > As to SSRs, not sure what you consider a "decent current rating", but a b= it > of poking shows this candidate - good to 50A - > http://www.digikey.com/product-detail/en/D2450-10/CC1082-ND/221775 or thi= s > one for 125A - > http://www.digikey.com/product-detail/en/H12WD48125-10/CC2007-ND/752475 > Though with your suggested loads > http://www.digikey.com/product-detail/en/S212S01F/425-2412-5-ND/720407 ma= y > be a more suitable choice. > > Good luck > -Denny > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .