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I live on the top floor of an apartment building with an extremely loud buzzer that anyone on the street can access day or night - and they do. I hacked into the apartment intercom station to install a potentiometer on the buzzer. It's working okay except that it doesn't go to zero because I can't figure out how to ground it. I only need a functional ground. Power to the intercom station is only 16vac. But what do I connect the grounding wire to??

My apartment building was built in 1852, and while the wiring was updated a few decades ago, it was mainly to install AC outlets. I don't think every outlet is grounded or there is grounding wiring running through the building.

I have very little knowledge of electricity - just enough to wire a dollhouse and make a few simple hacks. I've been reading for hours about how to solve this grounding problem, and I find only articles about what a functional ground is, not how to do it.

First I tried connecting the grounding wire to the back of the potentiometer, as musicians do, but that didn't work because it's not connected to other audio components that go to ground. Then (wild stab in the dark) I tried connecting it to one of the screws in the metal housing inside the wall (like what a light switch goes into), but that just caused noise.

What can I connect the grounding wire on the potentiometer to that will act as a functional ground? Anything?

I also bought an on/off switch that probably would work, but I'd rather live with low volume than have to choose between no volume at all or shockingly loud volume.

Thanks in advance for any help you can offer.

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  • \$\begingroup\$ Have you thought about using a pot with switch like this one? \$\endgroup\$ Dec 8, 2021 at 9:30
  • \$\begingroup\$ I've never heard of a potentiometer with a grounding wire. As far as I know, pots have three terminals: two end terminals and one wiper terminal. Does your pot have three terminals or four? If it has three terminals, then I wonder if what you're calling the "grounding wire" is actually the wiper terminal. I also wonder how you came to the conclusion that you need to ground your potentiometer, because I don't think that grounding a potentiometer is something that's commonly done. \$\endgroup\$ Dec 8, 2021 at 12:31
  • \$\begingroup\$ The POT has 3 terminals. Looking at them with the knob facing up, the far right is input to the POT (power source), the middle is output from the POT (in my case, the buzzer), and the far left is (I thought) the terminal for a ground wire. If that's not what it is, what is it? \$\endgroup\$ Dec 8, 2021 at 21:14
  • \$\begingroup\$ Rohat - the POT I'm using is very similar to the one you link to. I bought this: amazon.com/gp/product/B074KGJ7N6 One of the photos shows the far left terminal as the ground terminal, as I described in the previous comment. \$\endgroup\$ Dec 8, 2021 at 21:17

1 Answer 1

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schematic

simulate this circuit – Schematic created using CircuitLab

If you've connected the potentiometer in line with one terminal of the speaker, then the "ground" would be the other speaker terminal.

If it's connected as below, then the signal can never go to zero.

schematic

simulate this circuit

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  • \$\begingroup\$ If I understand you correctly, it's already connected that way. The POT is in line with the buzzer. One end goes to the buzzer and the other end goes to the wall. Currently the POT is acting as a rheostat because the ground pin isn't connected. My understanding (which could be wrong) is that if the ground pin went to ground, then when the wiper was at 0 there would be no sound at all from the buzzer. But I can't figure out what to connect that 3rd ground pin to to achieve this. Maybe a volume POT never turns off the sound completely. Or maybe I need a higher resistance POT?? \$\endgroup\$ Dec 8, 2021 at 2:35
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    \$\begingroup\$ @permutations See the modification to the answer. If the third terminal is connected to the "other" terminal of the speaker, you should be able to get the volume down to zero. \$\endgroup\$
    – Simon B
    Dec 8, 2021 at 9:00
  • \$\begingroup\$ @permutations You seem to be contradicting yourself: you said that "it's already connected that way," but you also said that one of the pins of the potentiometer is unconnected, even though the diagram shows all three pins being connected. Can you clarify what you mean? \$\endgroup\$ Dec 8, 2021 at 12:19
  • \$\begingroup\$ I apologize for being unclear. I'm not very knowledgeable about electricity, and I don't understand the meaning of the diagrams. What is R1? What does the jagged line mean? \$\endgroup\$ Dec 8, 2021 at 21:20
  • \$\begingroup\$ I don't know how to add a picture, so I'll try to explain better. I'm connecting to a buzzer, not a speaker. I believe it's an electronic buzzer. There is a single wire that connects the buzzer. It goes from inside the wall to a screw inside the intercom. I disconnected that wire and inserted a POT in series. The middle terminal (output) of the POT is connected to the buzzer screw. The input terminal of the POT is connected to the wire going into the wall. The ground terminal of the POT is not connected to anything. The POT wiper works to raise & lower the volume, but not all the way to zero. \$\endgroup\$ Dec 8, 2021 at 21:24

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