23 Aug
2015
23 Aug
'15
11:46 a.m.
Those ubiquitous motion detectors for outdoor lights use capacitive dropping to supply
the
low voltage for the ICs and electronics. Cap and small R in series with the AC input to a
bridge rectifier.
Works out well in that the bridge rectifier permits current flow in both directions,
which is
necessary to get current flow through the cap (the cap has to charge and discharge).
Over here that sort of circuit was common for the power supply for the control
electronics
in washing machines and the like. It may still be, I've not worked on anything that
recent.
-tony