2022-06-09

Shelly Plus 1 GPIO

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 I need just an input and/or just an output, for £15.99 I have a device that does the job. As an output it is a dry contact relay, and can be powered from 12V DC, or 24V-240V DC, or 110V-240V AC, so very flexible. Working with alarm system 12V DC or 24V DC is easy.

The input is run at "live" so for mains working needs a proper switch rated for mains such as a light switch (or one of the nice retractive switches). But working on alarm system 12V, a simple contact like a reed switch, or connection to a PIR is simple.

Obviously there are plenty of uses for the alarm system that needs more than one input or one output, but this is pretty useful. I even have one electrically locked door that is just using one for the lock and door open inputs as it is a door that does not need a fob, just needs to be locked when alarm armed, and detect door open as an alarm input ("access", causing alarm if armed).

My new EL560 locks on the house are great as no need for break glass or exit button as they open with the inside handle. But if you have any doors you keep unlocked during the day, you need a way to lock the doors at night. And that needs a button. Well, a Shelly Plus 1 is ideal. The light shows the doors have been locked.

I have also worked out the GPIO:-

  • GPIO0: Output for small LED (hard to see through case).
  • GPIO4: Input for SW signal (external switch) but needs configuring as pull down.
  • GPIO25: Input for small blue button on the case, but needs configuring as pull up.
  • GPIO26: Output to work relay.

There are also 6 external connection pins for programming (WARNING: THESE CAN BE LIVE):

  • GND
  • GPIO0
  • EN
  • 3V3
  • GPIO3 RX to shelly
  • GPIO1 TX from shelly
  • GPIO16

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