Electrical – Can dimmable (triac) LED bulbs be used on a motion sensor switch without neutral wire

electricalledlightingmotion-sensor

I bought a bunch of these motion sensor switches.

I also want to use these dimmable LED bulbs.

The motion sensors do not have a neutral wire connector. My outlets only have a live wire and it would be prohibitively expensive to put a neutral wire in.

I understand that regular LEDs flicker due to the trickle power from the sensor.

I want to know if dimmable (triac-compatible) LEDs would also flicker?

Also, if I buy the dimmable LEDs and they don't flicker am I ok to use them? Or will the trickle power damage them or shorten their life?

Best Answer

Reading between the lines ...

Where I live, a normal domestic lightswitch works like this

 Fusebox                  Ceiling                   Switch
 =======                  =======           live    ======
   Live  ----------------------o------------->------o/ o-.
   Earth --------------------o--------------------       |
   Neutral ----------------o | o----------<--------------'    
                           | | |      switched live
                           |   | 
                           \/\/\
                            bulb

(At "ceiling" there is a junction box / rose where wires are joined)

Because there is no neutral in the switch backbox, there is no way to complete a circuit there and power any active component like a PIR motion detector.

Incandescent bulbs have a low resistance when cold and off butr develop a high resistance when hot and on.

You can exploit this feature to power a gadget in the light switch, instead of a simple switch you add a high resistance load across the switch, this allows a small current to pass through the incandescent lightbulb when the switch is off. This small current is not enough to light the bulb (the wire inside is not red hot, it might glow a tiny bit though, depends on current)

     Switch
     ======
         /
 ----+-o/  o--+---.
     |        |   |
     '-/\/\/\-'   |
        PIR       |
                  |
 -----------------'

However, any kind of LED lamp is not going to have the characteristics of an incandescent bulb which are being exploited here. Your PIR motion detector is unlikely to work if the lamp is not incandescent.

If it does work, it would be because the LED lamp's internal driver circuit can work from lower voltages and currents - so you are likely to see some unwanted visible effects. It might be that some manufacturers use a type of LED-driver circuit that would allow your PIR switch to work but you may have to buy a lot of different LED lights to find one that does. You might never find one that does. Without knowing the internal details of the specific LED lamp it is difficult to make any predictions.

I notice that the advert you link to has a link to a replacement part whose description says it does work with LEDs. It is reasonable to infer the vendor is aware that the discontinued one does not.

Note on terminology:

Your Q was hard for me to understand because you are using terms in a way that is non-standard (at least in my part of the world)

trickle charge - is a small current used to slowly charge a car battery.
active wire - is not a term I've seen used in relation to household power.
outlet - usually means a 3-pin wall socket (not a light switch back-box or patress)

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