Comment on What is negative voltage?

• Onomatopoeia@lemmy.cafe ⁨5⁩ ⁨days⁩ ago

  First, the DC voltage of these fans is a separate voltage system from the AC/mains of the house.

  Whether the 12v comes from a transformer or a switching power supply, the DC and AC circuits are effectively separated by that device.

  The ground of the 12v system exists only within that system (and is provided by the transformer/power supply).

  Consider the tranformer/power supply to be a battery with a positive and negative terminal. Inside, a chemical reaction will take place that moves electrons from one set of plates to another, leaving “holes” in one set, and extra electrons on the other.

  This creates an imbalance - an electrical potential - and entropy says everything should try to balance. So those extra electrons provide the voltage, and once a circuit is made, will immediately try to balance the potential by moving through the circuit to the other terminal.

  Using a transformer/power supply provides those electrons (and a sink - somewhere for those electrons to return to) from AC/mains voltage.

  This is a pretty simple way to view it, there are more details that an EE would take me to task for, but it’s a good starting point.

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  • akunohana@piefed.blahaj.zone ⁨4⁩ ⁨days⁩ ago

    The ground reference of the 12v system exists only within that system (and is provided by the transformer/power supply).

    This was great! Thanks!

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• nous@programming.dev ⁨4⁩ ⁨days⁩ ago

  Nothing to do with the electrical grid. It is just that the positive lead of the output of the power supply is whatever voltage you select above the negative lead on the output side of the power supply. Those are the two relative points in this situation. You can call the negative lead ground if you want. Wiring diagrams for the device you connect it to will likely call it ground. It is not the same thing as the grounding wire in a plug socket.

  Note that the grounding wires in a home have nothing to do with any live circuit in your house. They are to make faults in the system safer by giving a path for electrons to flow if a conductive casing ever gets into contact with a live wire. In normal operation nothing should be flowing through it at all. With doubly insulated devices (like that power supply) the grounding wire in the plug socket is probably not connected to anything at all in the device. The plug likely does not even have a grounding wire in it.

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  • akunohana@piefed.blahaj.zone ⁨4⁩ ⁨days⁩ ago

    Thanks for the clarification! So, there is an overlap, then, when it comes to the term “ground”? Grounding - and its wiring - in the greater electric grid is actually there in case there is a ground fault, while ground wires in smaller DC circuits can refer to the “outgoing” lead/terminal/wire?

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