Twin Triac AC Switch on DP5050 PCB

Two triacs switched by zero-crossing optocoupled drivers act as solid state relays on a Dangerous Prototypes standard size PCB.


This design is released under Creative Commons Attribution Share-Alike 3.0 License. The schematic is based on a dual triac board created by RobG and posted to the 43oh forum. It suits snubberless triacs in a TO-220 package such as the BTA16-600W. This is not the best circuit for highly inductive loads due to the lack of dedicated snubbers. Please note that although BTA16-600W is rated 16 A and 600 VAC, the board will not be able to handle that much power. Current may be limited by the trace thickness and lack of heatsink space. The 2 mm clearance between tracks on the hot side is probably adequate for 240 V mains and should be able to handle spikes of at least a couple of kV, but is likely too narrow to handle anything higher. If desired, a random phase triac driver such as MOC3023 can be substituted for the zero-crossing driver MOC3041. The input resistor values are based on 5 V control signals.


Mains electricity can kill. If switching high voltages, make sure to mount this PCB in a well-insulated or grounded enclosure. For safety reasons it is a good idea to insulate the vertically mounted resistors on the hot side by covering them with heat shrink. It may also be beneficial to cover the finished PCB in conformal coating for additional electrical insulation and to protect against environmental damage. One option is to pot the board in a neutral cure silicone caulk such as GE Silicone II*. Make sure your loads are properly protected by fuses.



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