What is the mains supply voltage that feeds the power strip?
You can save 2 components by eliminating the top 2 diodes.
If you want to have the blue LED go off when the green LED comes on, you could try this (which uses only 1 more component than your posted circuit) :-
View attachment 90403
I wonder if the antiparallel diode is necessary. Damage from reverse breakdown occurs from heat as I understand it, not from the avalanche itself. During breakdown, the heat dissipation in the LED is about 24 milliwatts thanks to the series resistor and that will only occur for about 200 ns, the recovery time of the series diode, for an average reverse heat dissipation of 125 microwatts over one cycle of 60 Hz (which is much less than the forward heat dissipation). I do understand that the beginning avalanche region is very localized (non-uniform) within the junction area, creating tiny "hot spots", but with so little heat, I wonder just how hot the spots get.
The two-leaded, dual colored LEDs packaged and wired internally anti-parallel must necessarily experience brief periods of avalanche (if driven by, say, 10v or more through a series resistor) as the applied polarity is switched, given the capacitances and asymmetrical and finite switching times. I have wondered about the reliability of those if they are switched continuously to produce a mixed color.
Mr Al's solution works and is adequately protected.
ALL LEDs are rated for -5V and all will begin to fail with -15V, some will begin to fail with -10V.
However the LED current is ~ 1mA so it wont be very bright. Choose many 82K R's in parallel to increase brightness, each taking <0.2W full wave.
This is why Neon tubes are more popular than LEDs with 220K series R and 70V avalanche voltage for AC line detectors in extension cords.
MrAl,
I think I have a solution for you. I didn't figure the value of the resistor in series with the green LED as I am not sure of the current. After thinking about the circuit that is attached I think with a 5.1V zener diode in parallel with the 22uF capacitor would cover all possible failure problems.
Ned
MrAl,Hi Ned,
Thank you for the suggestion. What i am after here is simple construction and minimum parts count, and on top of that, high reliability. Thus i am going with parts that are known to have life spans on the order of 20 years or more. Resistors and diodes are high reliability devices when operated within limits, so it makes sense to stick with those components. Of course the circuit has to be done right too, and i have been playing around with this to get the right circuit
The zener is a pretty high reliability device too i think, so that may help somewhere too. I am still thinking about this circuit and not done yet really.
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