24 Feb
2010
24 Feb
'10
9:06 p.m.
Chuck Guzis wrote:
If you use a 'capacitive dropper' (as they tend to be known in the UK),
it's worth putting a high value resistor (1M or so) in parallel with the
capacitor to discharge it when you unplug the device. Otherwise, if you
unplug it at the right (wrong ?) point on the AC cycle, you'll get zapped
if you touch the plug pins.
-tony
There's some fellow on the web who's been
making various line/mains-
operated lights using only a resistor in series with a single LED.
Weird--I would have at least paralleled the LED with another
resistor. I'll try to find his web page, if anyone's interested.
I have on occasion run single LEDs from line voltage by paralleling the LED
with a diode, then putting the pair in series with a C and R. C is calculated
to provide most of the voltage drop via capacitive reactance, a small R is
still present to limit inrush current. The diode limits the reverse voltage and
permits bidirectional current flow so the cap sees AC.