Shelly Plus i4DC GPIO

As previously posted, I am quite impressed with Shelly stuff anyway, but the new "Plus" range has allowed some interesting developments - as they use ESP32, which is the processor I use for my access and alarm system.

This has meant I am able to add bits to the alarm system much more simply than using my custom boards - anywhere. As I reported before the Shelly Plus 1 is great as it can work on DC or AC, but this modules is specifically for DC usage.

The Shelly Plus i4DC, which is like the Shelly Plus i4 (which is AC), is powered from 5V to 24V DC. This is great news as it can work from 12V and 24V alarm systems, and the typical 13.8V of a battery box quite safely. You could even wire to a USB 5V supply.

It has 4 inputs which connect to GND, and this works well for connecting to fire alarms, door sensors, and so on, and can easily have spares for tamper and dummy wires. I would struggle to make something like this for the same cost, and when I factor in my time this is a total no brainer.

I have also worked out the GPIO:-

  • GPIO0: Output for small LED (hard to see through case).
  • GPIO12: Input for SW1 signal (external switch) but needs configuring as pull down.
  • GPIO14: Input for SW2 signal (external switch) but needs configuring as pull down.
  • GPIO27: Input for SW3 signal (external switch) but needs configuring as pull down.
  • GPIO26: Input for SW4 signal (external switch) but needs configuring as pull down.
  • GPIO25: Input for small yellow button on the case, but needs configuring as pull up.

There are also 6 external connection pins for programming which are common to most Shelly, and not mains live on this model:

  • GND
  • GPIO0
  • EN
  • 3V3
  • GPIO3 RX to shelly
  • GPIO1 TX from shelly
  • GPIO16
These can easily be flashed with tasmota too, use the ESP32 solo build. Note I cover two extra GPIO than the usual tasmota config (GPIO0, GPIO25).


  1. As i'm not on twitter or mastodon i can't message you that way.
    Been looking for a 12v "ups" dc-dc to keep router and NAS going in event of a power cut. Should be simple, use lifepo4 rather then lead acid battery and have two outputs. Only one i could find with reasonable reviews was Eaton 3S Mini DC UPS but only singlel output. This guy reviewed it https://www.speaktothegeek.co.uk/2022/06/review-eaton-3s-mini-dc-ups/ and raised a couple of points like would be good to monitor it via internet or API.
    Could this be a possible project for you to build a better 12v dc "ups"

    1. Surely for 12V you just get a battery box power supply, as used in alarm systems, and connect to as many 12V devices as you need. That is what I have here, well three of them for different parts of the house. They come in a range of power ratings. e.g. https://www.tlc-direct.co.uk/Products/DE640.html

    2. Maybe i'm over thinking it. I didn't want to use a 12v SLA but that could be simplest with a compatible charger


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