While 3D printers have evolved over the past two decades from novelties to powerful prototyping tools, the amount of support systems have advanced tremendously as well. From rudimentary software that required extensive manual input and offered limited design capabilities, there’s now user-friendly interfaces with more features than you could shake a stick at. Hardware support has become refined as well with plenty of options including lighting, ventilation, filament recycling, and tool changers. It’s possible to automate some of these subsystems as well like [Caelestis Workshop] has done with this relay control box.

This build specifically focuses on automating or remotely controlling the power, enclosure lighting, and the ventilation system of [Caelestis Workshop]’s 3D printer but was specifically designed to be scalable and support adding other features quickly. A large power supply is housed inside of a 3D printed enclosure along with a Raspberry Pi. The Pi controls four relays which are used to control these various pieces hardware along with the 3D printer. That’s not the only thing the Pi is responsible for, though. It’s also configured to run Octoprint, a piece of open-source software that adds web interfaces for 3D printers and allows their operation to be monitored and controlled remotely too.

With this setup properly configured, [Caelestis Workshop] can access their printer from essentially any PC, monitor their prints, and ensure that ventilation is running. Streamlining the print process is key to reducing the frustration of any 3D printer setup, and this build will go a long way to achieving a more stress-free environment. In case you missed it, we recently hosed a FLOSS Weekly episode talking about Octoprint itself which is worth a listen especially if you haven’t tried this piece of software out yet.

When you need to make very tiny measurements, even noise in closed relays can throw you off. [Marco] was able to observe this effect and wanted to build a switch that didn’t have this problem. He found a technical paper that used rotary switches operated by stepper motors instead of relays. So he decided to try making his own version. The video below shows how it turned out.

The first part of the video talks about why relays sometimes inject a tiny voltage into a closed circuit. He then looks at costly switches that would work. However, since he needed many switches, he decided to roll his own.

While this is painful, it does let you optimize for your particular application. That’s why it was important to understand why relays don’t work well in this application. Copying part of a design from a very interesting-looking switch, custom PCB switch decks arrived in the mail.

Did it work? Watch the video to find out. There was something very comforting about watching the switch rotors turn under automatic control. [Marco] reminded us that the switches look somewhat like an old auto distributor.

Measuring nanovolts isn’t for the faint of heart. With a little help, your existing gear might be able to read nanoamps, however.

Power distribution units, as the name implies, are indispensable tools to have available in a server rack. They can handle a huge amount of power for demands of intensive computing and do it in a way that the wiring is managed fairly well. Plenty of off-the-shelf solutions have remote control or automation capabilities as well, but finding none that fit [fmarzocca]’s needs or price range, he ended up building his own essentially from scratch that powers his home automation system.

Because it is the power supply for a home automation system, each of the twelve outlets in this unit needed to be individually controllable. For that, three four-channel relay boards were used, each driven by an output on an ESP32. The ESP32 is running the Tasmota firmware to keep from having to reinvent the wheel, while MQTT was chosen as a protocol for controlling these outlets to allow for easy integration with the existing Node-RED-based home automation system. Not only is control built in to each channel, but the system can monitor the power consumption of each outlet individually as well. The entire system is housed in a custom-built sheet metal enclosure and painted to blend in well with any server rack.

Adding a system like this to a home automation system can simplify a lot of the design, and the scalable nature means that a system like this could easily be made much smaller or much larger without much additional effort. If you’d prefer to keep your hands away from mains voltage, though, we’ve seen similar builds based on USB power instead, with this one able to push around 2 kW.