I used to build those things in the dark, distant past. I used MOC3010 opto-triac back then (now-days I would use a MOC3011) in place of the original SCR. Worked extremely well. The majority of the strobes that I used to modify used a pot wired up as a voltage divider feeding a RC time delay which then triggered a diac which in turn fired the SCR. The reason I mention this is because I found it useful to NOT remove the original SCR - just leave the pot set all the way OFF. That disabled the original self-contained flashing and allowed complete remote control of the strobe via the opto. The triac in the opto was simply connected in parallel with the original SCR. The advantage of doing it that way was that the strobe could still be used for its original purpose. I still have a bunch of those strobes around - I now use them for bright call indicators for Intercom systems. The reason I modified strobes that I purchased instead of building from scratch were several: existing certification on the purchased strobe meant that getting the modified strobe certified by the local inspection authority was relatively cheap and, most important, the purchased strobe cost far less than the parts cost and labor for me to build from scratch. The last time I purchased these, I think that they cost something like Can $10.00 each at the local grocery store (they were being sold just before Halloween). They even came with 3 different colored gels that could be slid over the front. Hope this helps! dwayne At 06:19 PM 7/5/2009, Jinx wrote: >In Figure 3 here > >http://www.rory.co.nz/projects/lighting/beat_strobe.html > >the author specifies an H11D1/H11D2 optocoupler, which has a >Vce of 300V, as described in "Opto-coupler Selection" > >None of my usual suppliers have the H11D1 or 2, and AFAICT >none of their other opto-transistors have Vce greater than 70V. It >isn't possible to do a quick search because output voltage isn't one >of the parameters, only isolation voltage and output current. Only >by downloading all the datasheets > >Is there a reason why a MOC3020 opto-triac couldn't be used ? -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist