High Voltage

  • I've read (and checked) that on the shelly1 the gpio ground pin is directly connected to the N pin. So it should not possible to use the gpio when the shelly1 is powered with 240V AC. Is it true?

    Can the temp addon be used when the shelly is powered with high voltage? Or it is usable only with 12V power supply?

    What are the dangerous on doing that and which are the operations that absolutely must be avoided wen powered with high voltage?

    This part related to the security is not well documented and it is very important in my opinion.

    Could you explain the differences in connections and power supply?

    I found some information here, but still it is not clear to me:


    "The shelly 1 GPIO cannot and should not be used while connected to mains voltage. While the sonoff makes reasonable efforts to isolate the high voltage and low voltage side of the board, the GPIO headers on the shelly are directly tied to the AC lines. Specifically the ground on the header is tied directly to the hot wire or line voltage pin from the AC input. I repeat, do not ever attempt to use the GPIO header of the shelly 1 when it is connected to mains voltage because the ground is referenced to your mains voltage."

    Thank you in advance for your help on this


  • Hi and welcome to the forum. :)


    Can the temp addon be used when the shelly is powered with high voltage? ...

    With 230V, you can use it. :thumbup:

  • Hi, thank you for your response.

    But how is it possible?

    Why the L line doesn't interfere with the ground pin of gpio?

    I am interested in understanding exactly this part.

  • Perhaps, anyone other can explain it.

    I can't, sorry.

  • Hello emabiz,


    1. All Shellys are working on the voltage of the supply voltage level
      ==> therefore it would be dangerous to connect anything direkt to the GPIO-pins and may
      destroy the connected equipment
      ==> even the antenna must not be extended to outside of the Shelly housing
    2. The Temp-AddOn was exactly developed to isolate the sensor inputs from the supply voltage, doesn't matter which voltage level is used. It has no galvanic connection with the supply voltage because of the use of opto-coupplers

    Grüße Bernd

    Mein "Smarthome":

    FHEM als "Master"(Cloud-Free :))mit 85 Shellys(1, 1PM, 2, 2.5, 4Pro, RGBW2, PlugS, alle mit Original-FW),13x Sonoff (Tasmota-FW),12x Blitzwolf/Gosund(Tasmota-FW), 85x One-Wire Temp-Sensoren(16x D1-Mini mit Tasmota-FW),51x Modbus(Hutschienenzähler),31x Intertechno 433MHz(Rolladen-Aktoren),12x FBDECT(8 Heizkörperthermostate, 4 Schaltsteckdosen),21x Homematic(16 Raumthermostate, 3 FB-Heizungsaktoren, 2 Repeater),etc. ...

    Neues von Print Worth 3D: ==> Marktplatz

  • Hi,

    thank you.

    In the meanwhile I opened the addon and I've seen the 7221A.

    Congratulations for the design. It is very versatile.

    I am a bit worried to keep it supplied at 240V AC so maybe I will use an external 12V DC adapter that is ok for my application.