Normally, when a low DC voltage is required from an AC main supply a transformer is used.
However, [RCD66] noticed that a domestic AC monitor meter’s power supply did not include one, prompting an investigation and a YouTube video on how it works and how to use it.
Practicalities mean that the monitor meter’s power supply is unlikely to be used in other projects, but the exploration is interesting.
Be aware that building a transformer-less power supply involves risks and requires careful consideration and understanding of the risks.
Transformers provide isolation because the primary and secondary currents are not referenced to ground, whereas a capacitor only limits the current and the return path can still go through a person’s body.
Using two capacitors in a balanced arrangement does not provide isolation because both sides are still referenced to ground.
