Power Strip Relays

At the time of building the project, in addition to controlling water pumps, I wanted my Arduino to control both a heater and chiller.  These devices draw of power (200 and 900 Watts) so it was important to have power strips and Solid State Relays (SSRs) that were rated for high amperage.  I went with DJ power panels that were rated for 15amps, and also included built resettable infuses in the event there was ever a problem with something plugged in.  

Below you can see two of these power strips facing out of one of the cabinet doors.  Power switches mounted like these have been very handy for maintenance over the years.  Every time I do cleaning or water change, I just flip off the return pump, skimmer, wave powerheads, auto-top off, and lights in one easy-to-access location.  


About half of the power outlets on these power strips are switched automatically via the controller.  You can see five TIP 120 transitors (of ten used in this project) in the photo below which I use in switching the solid-state relays used in my power panel.  There is a good tutorial on this circuit on the instructables site and this ez-robot forum.  This circuit is a low-cost way of driving higher voltage switching, which was needed for the solid-state relays I selected, from the low voltage Arduino.  

💡Lesson Learned: In retrospect, I would have looked for SSRs with switching voltage that matched the 5V Arduino output so the TIP 120 transitors would not be needed, but I ordered the SSRs before I realized that was an issue.


The following is a quick video showing the SSRs in action using a float switch to trigger an outlet, which for this test is just connected to a lamp.


Almost all power strips have solid, inflexible connectors between outlets, which are the large, straight copper wires you see running horizontally in the photo below.  On the very far right of this photo, you can see one copper wire running vertically in the photo, which is one of the outlets not switched by an SSR.  Originally all the outlets looked like that, and to convert the box I cut those short copper wires out and ran the black wires you see running to a hole in the lower left.  

WARNING: If you attempt this, please understand this is high voltage and very dangerous.  Additionally, if you do not use the right wire gauge (thickness) you risk a fire.  Don't try this part of the project unless you know how to work with high voltage, which this blog does not cover.


The black wires carrying high voltage exit the inside of the power strip through a hole, with a rubber grommet inserted to ensure the wire is not cut by the box, to the SSRs that are mounted on the underside of the box. 


The low voltage switching lines were connected to the SSRs and then to the D-sub connector that is later plugged into the controller box.








Finally, all ten of the SSRs, five on each of the two power strips, are shown below connected to the controller using the d-sub connectors plugged into the ports on the side of the project box.