Home3D Printer UpgradesShelly 1PM: "PM" stands for Printer Manager

Shelly 1PM: “PM” stands for Printer Manager

It was made for lights, but I have a better idea

Time for another forgotten-by-me, device. Shelly 1 PM has been waiting in a box of switches (yes I do have one of these!) for some time. This connected relay is a brainchild of Shelly 1 (review) and Shelly 2.5 (review). Unfortunately, PM stands for Power Monitoring, not Printer Manager, but if you read more, you will quickly understand why I decided to butcher its name in the headline. I really hope this will inspire you to use Shelly 1 PM in a creative way.

Shelly 1PM

Power monitoring isn’t the only difference between Shelly 1 and Shelly 1PM. In fact, there is another, much more important change. Unlike the original Shelly 1, Shelly 1PM doesn’t come with decoupled relays. This feature alone puts Shelly 1PM closer to Shelly 2.5 – where the only difference between these two is the number of relays inside.

Shelly 1PM in detail

Just like the original Shelly 1, this device is tiny. It comes with mains pass-through, which means it will deliver the input voltage to the relay’s terminals. Here is the basic hardware specification:

  • input 110-240V ±10% 50/60Hz AC
  • input 24-60V DC
  • output 16A/240V
  • WiFi 802.11 b/g/n
  • various switch modes

Designed to toggle lights, Shelly 1PM fits in most electrical boxes, assuming you have extra space for electrical connectors. That’s the only issue I take with Shelly devices. They are the smallest out there, but due to the minimal number of terminals, you will end up using extra WAGO-type connectors. It’s an argument that sparked a big discussion when I compared Shelly 1 to Sonoff Mini.

As the device can handle up to 16A (resistive load), it’s perfectly suited to drive my 3D Printer, and your lights, sockets or any other creative uses you will come up with. Go nuts! In case you want to take things further, Shelly 1PM just like its siblings comes with dev pads exposed: GND, GPIO00,3.3V, RX, TX. It’s unlikely you will be needing these as the next best thing is Shelly Cloud.

Inside you will find the familiar ESP8266 IC governing the relay. There is already a Tasmota release for Shelly devices, but going through all this just to replace the existing MQTT and REST support seems rather pointless. Read the next chapter before firmware changes.

Shelly Cloud

It’s going to be 3rd time I’m praising the same thing. I will spare myself sounding like a broken record. Load up the Shelly 2.5 review and you will see why Shelly Cloud should be considered a standard!

If opening those links sounds like a chore, here is a list of things that are cool:

  • Shelly Cloud app with smart assistant integrations
  • the usual timers schedules and toggles
  • REST API triggers based on inputs
  • LAN only mode
  • Web Sever which offers pretty much the same functions
  • MQTT and HTTP integration of the box
  • all switch modes support every switch you could dream off (from pulse to toggle or disabled)
  • Power monitor in W and Wh
  • total room consumption

I will be taking the advantage of MQTT and the power metering features. Unfortunately to use MQTT I will have to sacrifice the Shelly Cloud. It’s not a massive issue for me as I will resolve everything via NodeRED. I already have articles about the integration of Alexa and Google Home in NodeRED so it’s going to be a piece of cake!

PM = Printer Manager

I’m talking about Shelly 1PM for a number of reasons. Shelly Motion (review) just got released, and I promptly realised I never got to talk about it. On the other hand, I spent the last few weeks upgrading one of my 3D Printers- Ender 3 v2 (review), trying to bring it closer to my kitted-out original Ender 3 (review) which has an array of cool upgrades.

While Ender 3 v2 is nearing perfection with the BL Touch, filament runout and all-metal hotend upgrades, there had been 2 issues affecting my Ender 3, driving me nuts:

  1. Inability to upgrade OctoPrint
  2. Bulky Sonoff POWR2 that handled power control and metering

This is where Shelly 1PM came in handy. Thanks to the small footprint and similar to Sonoff POWR2 (review) features, I was able to hide the switch inside the power supply and fix my OctoPrint Undervoltage issue. This in turn will enable me to modernise the OctoPrint supply which caused the Undervoltage case (back then, under-voltage wouldn’t lock updates) and still deliver printing notifications, auto shutdown and cost of print calculations that include the price of the electricity used. A perfect combo for anyone thinking of turning their 3D printing hobby into a small business.

I realise that many of you will try to make a compelling argument for using smart plugs instead, but let’s face it: my printer will be way cooler than yours thanks to the approach I took! Being cool doesn’t need are reasonable argument to win the discourse! 😁 (I’m winding you up – so by all means use plugs if you prefer to!).

What’s hiding inside?

There are 2 systems at play, at least on my Ender 3. First, I had to discard the 220V->5V converter I recommended in this article due to under-voltage. It powers a Raspberry Pi board hidden inside the modified enclosure. I was looking for some time a suitable power supply to replace this with, and then it hit me! I could simply destroy one of the spare (and incompatible due to non-UK plug) chargers, hardwire it, print a 3D printer enclosure and enjoy the free, regulated 5V to power on my board.

Secondly, I needed to open up the plastic cover that holds the ICE socket. To completely take over control of my printer’s power system and detach the physical switch, I needed to rewire it inside. It’s not a difficult task, but do take extra care if you are going to do so, as it involves main voltage. Consider yourself warned!

On the surface, the printer looks completely innocent. The power switch works as intended, and if not for the makeshift Raspberry Pi supply, you would never tell that the printer is modified! Thanks to OctoPrint and MQTT I can turn on/off the printer at will. I already created a notification system that handles this for me and uses power metrics to calculate the real cost of the print.

Get Shelly

Check out other devices from the Shelly series to build your ultimate DIY automation:

Final thoughts

I don’t expect you to follow along with my insanity, it’s a fun little project I wanted to complete. The main purpose of this mod is to show you that Shelly 1PM is a very useful little device even if you are not planning on automating your lights. After all DIY automation is more interesting when we find exciting new ways of repurposing products to suit our needs. If you got inspired by this project, let me know and tell me what you come up with. Leave your story in this Reddit thread.

🆓 📈- See the transparency note for details.


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