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I'm doing some Home automation and am currently trying to automate my intercom system. My overall aim is to be able to detect when someone has pressed the buzzer and then to be able to open the door if I so wish. Below is the diagram of what I intend to do:

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For reference, the buzzer board above is the is the Tegui 1378/1. The documentation can be found (in Spanish) here. I have been able to conclude the following so far about the pins:

1E: Buzzer

2: Common (12V dc)

3: Door lock

4: Microphone

5: Speaker

However, I have been unable to find any GND on this board. As a result, my diagram above makes use of the GND supplied on the NodeMCU instead; is this okay?

Whilst digging around, I found box in my main fuse box called a Tegui E-30. I believe that this takes in mains and drops it down to 12V for the intercom system. It has two pin outs simply labelled "9" & "10". Now, I am fairly sure that one of these is positive and the other negative; in which case, this would explain where the ground has been but I am unsure. It would be handy to know if it is the case that they are positive and negative respectively as it would be more convenient powering the NodeMCU from the 12V (after dropping it to 5V) rather than getting a massive USB cable from the other room.

I would really appreciate any more information people could give me. Both in terms of whether the above diagram would work but also whether someone can have more luck than me finding out exactly what the "9" & "10" pins on the E-30 are.

Thank you in advance for any help!

Kind regards, Rocco

  • are you sure it is 12 V DC? door bells traditionally use 12 V AC to buzzzz – Juraj Aug 28 '18 at 16:35
  • from the manual "Características: 12 Vac. y 880 mA." see "ac" – Juraj Aug 28 '18 at 17:13
  • Thanks for your response! I hadn't seen that before; I'd simply done a "Find All" for 12 and had seen a few 12 Vdc but no 12 Vac leading me to assume it was DC but I appear to be incorrect. I've just seen that on the E-30 box, it reads PRIM 230V ~ 50/60Hz 20VA SEC 12V ~ 1A, I assume the ~ refers to AC, am I correct? – Rocco Aug 28 '18 at 17:27
  • yes ~ is for AC. I am sure you can find and buy 12 VAC to USB power (5 VDC) adapter to power the NodeMCU. – Juraj Aug 28 '18 at 17:35
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    I would use a relay to activate the lock and a current sensor or optocoupler to detect current to buzzer. this eliminates the need of common ground – Juraj Aug 28 '18 at 17:45

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