Home>Discussions>ELECTRICAL & LIGHTING>Motion Detection Switches & CFL Flicker
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Fencepost
Re: Motion Detection Switches & CFL Flicker

I think you're on the right track, Maurice.

In order to power a two-wire motion sensor, it must pass its return current through the light bulb since it doesn't have a connection to the neutral wire. CFLs don't do a good job of allowing this current; they'll flicker because of voltage that passes through the motion sensor when it's off.

A three-wire motion sensor (not to be confused with 3-way) includes a neutral wire for the return current that must be connected to a neutral line. This allows the load side of the sensor to be completely unpowered when off so the CFL won't flicker.

Moral of the story is it's best to use a 3-wire motion sensor and run a neutral to the switch box so you can use CFLs with it.

sausage
Re: Motion Detection Switches & CFL Flicker

I am using a motion detector in my garage with three porcelain ceiling bulb fixtures. I tried an LED for the second time in one of them. The switch will not turn the LED bulb off. The LED will go on when motion is detected but will only dim down (as if it is getting less voltage or current) to a low light and stay that way when the switch stops detecting motion. Is there a trickle current that lets this happen? I like the LED in the garage but cannot see the energy efficiency if the light does not go out.

Re: Motion Detection Switches & CFL Flicker

Sausage, the motion detector uses a transistor (Triac) to turn power on & off to the light bulb but because the CFL or LED draws so little power it can't function.

As Fencepost said the device w/ 3 wires probably uses a relay output rather than a Triac so they work fine.

I had a closet w/ two 60W incandescent lights on an occupancy sensor and like yours, the CFL's I installed wouldn't go out.
I re-installed one of the 60W bulbs (loaded the circuit) and now everything is fine.

Spending the extra money on CFL's or LED's is hard to recover because the lamps only come on for a few minutes at a time.

William
Re: Motion Detection Switches & CFL Flicker
skrillet wrote:

Will led light bulbs also flicker on a motion detecting switch?

You need a switch rated for LED's. I know Cooper makes some (OS310U).

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