For a number of my upcoming projects I need a rig to test the functionality of a solid state relay that would be driven by a microcontroller and switch the mains for other devices. Having done projects with similar requirements in the past I remembered how much pain it was to test the solid state relay (SSR) with naked mains cables running around, etc. This time I decided to create a marginally more sophisticated setup that would allow a quick, easy and safe way to do this. Also, now that I have made this once, I can reuse this rig in any future project with zero effort. Making this took about a day’s work – most of the time was spent on finding materials that suited my needs.
|This mains output is switched by a solid state relay, baby! 🙂|
Most of the parts I have recycled from old, discarded household devices, computers, etc. The only item that got specifically for this project is the solid state relay or SSR: it’s a cheap one that can handle 25A on its switched end.
An old, non-working printer (?) power supply has kindly donated its enclosure for this project. I just needed to make some minor adjustments for the sockets and cables passing through it and the enclosure story – the most difficult part of any project (for me) – was over!
As the mains input I chose a PC power cable, just cut off the end (that usually goes into the PC) and connected it directly to the appropriate terminals.
For the switched output I salvaged a female, panel-mounted 3 pole socket, recycled from an old and unusable UPS.
The control signal arrives to the unit through another cable borrowed from a non-working printer – I even left the barrel plug on it, so that I can easily connect to my bread boards easily.
Finally, I used some sticky rubber feet salvaged from some old satellite receiver so that it can stand nicely, without scratching whatever it is on.
First I gutted the power supply – I kept some parts from it for future projects and threw away the rest. Then I laid out all the components in it to make sure everything fits nicely. Using a Dremel I widened and deepened the hole on the sides for the (output) socket and the (input) cable.
Also, with the Dremel I created 3 new holes: one on the side for the cable of the control signal and two on the bottom for fixing the solid state relay.
|These two screws hold the solid state relay in place.|
|The solid state relay is already secured and the control signals are attached.|
It turned out that the output socket was too high and did not have any support at its bottom, so I cut a couple of rectangle shapes (of the dimensions of the socket profile) out of some left over 1mm thick polystyrene sheet and I superglued them to the bottom of the socket to provide a solid base for the socket.
|While the glue was drying a huge “peg” was holding it in place.|
|When dried the base is so strong I couldn’t tear them apart with my hands.|
After this only the connections had to be made which are trivial:
|All the mains connections in place.|
|I created a small circle of hot glue on the input and control cables to prevent accidental cable strain.|
|The input and the control cables.|
After attaching the sticky rubber feet it’s ready for the next experiment!
I could have complicated the circuit a bit further. An LED on the enclosure showing if it’s on or off would be nice (the enclosure even has a dedicated place for it), but in my case it’s not necessary as the switched circuit will give feedback on the state of the relay. I could have used sockets and connectors on all IO. I decided not to so that it’s simple and compact.