Trying to make a STR WF 26/G doorbell smart. Too low voltage?

    • Autor

    My apartment was built in the 90s and has an older doorbell system that allows me to hear and speak to visitors and remotely open the building door.

    Model: Sprechstelle STR Wohnungssprechstelle WF26/G. Schematic (in German)

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    I hoped that connection 1 and 2 could be used to power a Shelly Uno to make the doorbell smart. I would like to get notified when someone rings the doorbell.

    Between connection 1 and 2 of the WF26, I measure 11.1V with a multimeter without attached Shelly Uno.

    After attaching pin 1 and 2 of the Shelly Uno to the connections 1 and 2 of the WF26, the Shelly Uno led lights up for a second, and then starts flashing.

    With the multimeter, I now measure ~5V, fluctuating between 3.8V and 5.6V.

    No WiFi network is to be found to set up the Shelly Uno.

    Does this mean that the voltage from the WF26 is too low to power the Shelly Uno?