Solid State Relay (SSR) Circuit

The solid state relay is pretty much just a Triac, optoisolator and a couple of resistors. Here's the circuit diagram for one of them below:

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Althought the SSR is capable of switching 240VAC, it's more than capable of switching safer lower voltages at 24v / 35v from the secondary side of the transformers as well. The 150ohm Resister & LED are optional and can be removed, however I think having it there makes diagnosing faults, programming and general setup testing a lot easier.

The cheapest place to buy the Triacs from is Jaycar Electronics.
The cheapest place to buy the rest of the parts is from Wiltronics.

Below is a picture of one of the SSR boards during construction. The status LED, heatsink and wiring haven't been added yet.

A bank of 11 SSRs during construction.

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