I am trying to use the optocouplers to switch 12 volts DC. Can the triac switch DC? If not what transistor should I use with the K2634 set up?
If not is there a optocouplers relay board I could buy?
Triacs do not switch DC!
If you have relays, there is no need for opto-couplers
Please let us know what your application is, maybe we have a circuit that suits your needs.