in full wave rectifier without transformer how can access to gnd for regulator or gnd of microcontroller? (assume we dont have trouble with amplitude of voltage) I think in full wave rectifier in negative part of input voltage cycle, the negative rail in rectifier have voltage that could be dangerous!
closed as unclear what you're asking by winny, brhans, Dmitry Grigoryev, Transistor, Chris Stratton Sep 3 '18 at 18:09
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Both DC output terminals of a bridge rectifier will be "hot" relative to its AC input terminals. If the input is the AC Line, without a transformer, neither side of the output can be connected to AC Neutral or Earth.
You will probably use the negative side of the DC output as your "Circuit Ground", but the whole circuit must be insulated from outside contact as the whole thing will be "Hot".
You should consider that after the full bridge rectifier we have a filter capacitor. you should use a polarized capacitor with x 10uF ( depends on your application ). so the GND will be the Negative side of the Cap. Note: linear regulator are recommended to get a stable DC voltage.