yes, they are an optical trigger.
I would need an help in comparing and determining if they are all equivalent in functionality or if one is better than the other two. Flash voltage is anywhere from 2 to 300V.
thanks.

 

Hello,

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Bertus

 

sorry, didnt realize it wasnt showing, i could see it in the post but probably was because it was in the browser cache

 

Looks like homework. What are your initial thoughts and why? Give us that much and you will get some guidance.

 

no its not homework, i used to know this stuff when i was in school, the 2 30Mohm are supposedly to not drain the batteries of the flash unit, i have been told that they should not go directly on the negative end but not why, so i asked for help while in the meantime im dusting off the little i remember to figure it out. Thats all...
I was gonna say that if it was homework i would have posted in an "homework" section but i guess there are students that post in other sections to get their stuff done.

 

To not drain the batteries of the flash unit, i would have put the resistors in series with the circuit but those would have been too big anyways, one of my thoughts was that maybe the two 30M resistors are in parallel to keep the current in the SCR low enough to not latch continuously after the first shot... and for that i would have kept them like in C although i dont think enough current would remain at the trigger contacts. I have the impression that in series with the photodiode they would alter its sensitivity rendering it unusable, the resistors i have seen used to regulate the sensitivity are like 1Kohm not that big.