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The question I have is maybe silly, but I cannot find strictly related info.

When designing a mains switch with an optotriac driven triac (or discrete SSR for you), during layout I swapped the terminals of the optotriac. In my circuit Line connects to Pin4 of U3 through resistors, and gate drive is Pin6, instead the other way around. Could it make any problems with the zero-crossing detector inside the optotriac? Should not I think, but every doc (datasheet, application note, etc) I find on the net does not swap these pins.

The circuit is hereSSR Optotriac circuit Note: Main triac is a "Snubberless" triac as ST calls them, so leaving out their snubber is intentional, only phototriac is guarded!

The sake was the (hopefully) clean layout as seen. I have three more identical switch circuit to the left right connecting to the big Line and Neutral tracks. Grid is set to 1mm. Low voltage side connections not routed, passive values not calculated.

SSR Optotriac layout

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  • \$\begingroup\$ You had better breadboard the design with any possible load. Trigger and load ports are defined in polar quadrants I, II, III, IV and swapping these also swaps quadrants. Some work better in I to III only. \$\endgroup\$ – Sunnyskyguy EE75 Nov 7 '17 at 17:05
  • \$\begingroup\$ Thanks for you comment! You mean swapping main terminals mirrors quadrant diagram by X-axis, so swap I<->IV and II<->III, but correct me if I am wrong. Main triac (D7) should wired correctly, meaning it will be used in quadrants I and III as I just checked. That one cannot be used in IV, that's a price for not needing a snubber in most cases. Phototriac shoud be able to work in all quadrants. I hadn't checked till now that \$\endgroup\$ – Krisztián Szegi Nov 8 '17 at 8:07
  • \$\begingroup\$ Also, note that circuit seems wrong for D7. KiCad only has one triac symbol with PIN3 as gate (triac-AAG or MMG). Using that, A2 (or M2) goes to PIN1 by symbol convention. But in reality, A2 (or M2) maps to PIN2 of the triac's TO-252 package. I should report this on KiCad lib github \$\endgroup\$ – Krisztián Szegi Nov 8 '17 at 8:25

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