Solid State Relay to Switch Transformer?

[irving2008]

I used to avoid triacs because of the need to retrigger them constantly to keep the power flowing but the opto-isolated triac makes that so easy. LED on = power flows.

That's why they made the MOC3040, a zero crossing variation of the good old MOC3020. It has no meaning other than as a switch.

I got the MOC3020 + power triac + 1 resistor circuit from an old RS catalogue which detailed an SSR they were touting. Okay they might have moved on since then but you can still build an opto isolated 25A mains switch for around a quid.

I used the circuit to switch on a half horse cap start motor which leapt convincingly until I bolted it down.

Just had a look at the data sheet for a MOC3040... its turn-on volts is 20v so not truely zero-crossing but as near as makes no difference. But at 43p, coupled with a 97p 60A continuous-rated 600V triac and a 330R resistor its a good way to switch spindle motor or similar...