I like to breadboard and test many different types of projects. For a while I was doing a lot of home automation things trying to cut down on my electric bill while not sacrificing creature comforts. Controlling an A/C or large heater takes a bit of care. luckily there are solid state relay modules that do most of the work for you.
Since I use so many of these Solid State Relays I made a nice test box to help in the design phase. I've used these to control routers, vacuums, lighting, chargers heaters and more.
Step 1: First Generation
This is the first one I built back in the 90's. it was still working last week when I tripped over it and pulled the ac cord out of its grommet. i opened it up and it looked fine but it had some limitations. There was no heatsinking so i was limited to 400 watts per socket. I decided to rebuild it rather than repairing it. These solid state relays were removed from an old computer disk drive with 14" removable disk pack. I have a bunch around since it was company policy to replace all 3 when one failed. Every service call yielded 2 good relays for the scrap box.
Step 2: Second Generation
I salvaged an AC panel from an old UPS and got a new enclosure from Radio Shack. That is the only part that wasn't recycled. I used a scroll saw to cut out the center of the lid to accept the UPS panel.
Step 3: Heatsinking
I mounted the relays to a scrap piece of 1/8 aluminum plate. It's more than enough. these things will never come near their limit of 45 Amps at 240 Volts. I like to use relays that allow 3-30 V input. They work well with Arduino's and Pic's but can even be used in 12 V and 24 V circuits.
I ran a ground wire from that plate to the UPS panel and the line cord for safety