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171 posts

Master Geek

# 205739 25-Nov-2016 00:38
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Interesting phenomenon, I have some LED corn lightbulbs (from DX), which have 48 surface mount LEDs.  Two of these are in a hallway set up with 3 different light switches.


When one of the switches is in a particular position, and I turn the lights off using either of the other switches, most of the LEDs stay dimly lit on each of these bulbs, indicating that there is a low voltage being fed to them still, but not enough to light them all fully.  Other non-LED bulbs on the same circuit do not show any sign of life.


If I turn that particular switch to the other position, then switch the lights off on the other switch, then these lights will go dead.


I haven't worked out the circuit required to have 3 different switches controlling the lights, but I am guessing that one of the lines most likely runs close to the power supply for my hot water, and could be getting a small charge by induction.  Is that likely?  What other causes could there be for this charge on one part of the lighting circuit?


Should I get this investigated by a professional or ignore it?


And before you ask, no I haven't yet done the logical obvious test of turning off the hot water cylinder to see if the lights then go dark.  Must get off my butt and try that sometime.


[Update:  I switched of the hot water and it made no change, so the charge is coming from elsewhere]



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2986 posts

Uber Geek

  # 1677141 25-Nov-2016 07:01
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You don't need another circuit. If reordering the straps doesn't fix it some electricians add a capacitor.

171 posts

Master Geek

  # 1677937 26-Nov-2016 15:18
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Wow thanks, that was exactly the issue.  


I'm not concerned with the effect, unless it is likely to damage these bulbs.  Prolly not good for them.




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Uber Geek


  # 1677969 26-Nov-2016 15:47
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Completely wrong explanation for it, but yeah that is the cause of it. It is actually capacitive coupling between the cores of the wire, nothing to do with the loop as there is no current flowing in the wire that they are looped around it cant inductivly couple.


I have a huge length of 3 core between switches at 4 doors into the lounge and with some cheap flickery capactive dropper driven LEDs then it is a bright enough glow to actually cast shadows you can see in the middle of the night. Just a few microamps into LEDs and they are incredibly efficiant.


171 posts

Master Geek

  # 1678071 26-Nov-2016 18:49
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ah induction, capacitance, resistance is futile etc.


Capacitance makes more sense tho, as I was trying to work out what flowing current could be causing the effect.


At least it makes sense that it happens on one side of the center switch but not the other.  Now I know the center switch in a 3 switch setup is different than the end ones, too.





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