When completing an audit, a customer told me that when he installed a LED lamp in his outdoor fixture with a motion sensor, the fixture would start flashing faster and faster until it looked like a strobe light.  I have just recently noticed the same thing with a neighbor's outdoor light that utilizes a motion sensor and I assume he has put in a LED lamp.

Has anyone else noticed this with outdoor lighting with motion sensors and LED lamps?

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My first thought is whether the motion sensor and/or the LED lamp is a cheap one. I had so many problems with cheap or inexpensive motion sensors that I was installing for clients that I started buying RAB brand. It has been probably 15 years and I have had only one callback. RAB quickly sent me a replacement under warranty. LED lamps should be EnergySTAR labeled to avoid the cheap ones that can cause such problems.

I have installed several RAB motion sensors with Phillips LED flood lamps in the past year or so. I have had no problems, even when the temperature is below zero. Make sure that the lamps are specifically rated for outdoor use and for wet locations, if applicable.

That makes sense since the same thing happened with dimmable CFL's.  I have never heard of the RAB brand.  WHat does RAB stand for?

I don't know what it stands for. See RAB.com

Do you mean https://www.rabweb.com/  

yes, that is the website for RAB Lighting


As a former electrician I second your comments on the RAB products. 

As with any motion detecting device, make sure the light source (LED) is not too close to the motion/light sensor. If so, if could cause a "feedback" behavior, similar to what you described.

Yes,  and the reason why it is occurring is that the motion detector is powered only through the light bulb.  There are several ways to solve the problem.

1) feed back to the daylight photo sensor (easy to test... cover it with tape)... but not likely these should be slow responding signals.

2) use a motion detector/light-bulb combination that are designed as an integral device.  (Probably not going to happen in this case)

3) Try a different brand LED (I'll explain later) -- don't use a dimming light bulb in the socket.

4) Check/change the motion detector so that the detector has both a hot and neutral going to it... with the hot switched output of the detector going to the bulb and the same neutral that is powering the motion detector also going to the bulb.

The reason why the always on HOT and NEUTRAL to the detector is important is that it is a very low power device... the typical motion detector that was designed for incandescent light bulbs depends on using that incandescent bulb to provide a "neutral" to the detector.  Typically they use a triac and use the voltage drop across the triac (even when its turned on) to provide the power needed to operate the detector.   But LED bulbs use so little power AND they also more or less have a similar circuit that is expecting to harvest some leakage power to run the LED dimming/driver.   The blinking is probably occurring because the LED driver is successfully scavenging some energy through the detector -- but not enough to stay fully lit.  It it blinks at a high rate.

Changing to a NON-Dimming bulb can often change the blinking -- but depending on the motion detector it may result in an outdoor light that appears to be on all the time albeit dimly lit.  If that occurs and the LED was not designed for the partial supply -- its lifetime will be compromised and the driver will fail in weeks or months (I've seen this happen multiple times).

Changing a motion detector so it has it's own neutral -- and one that uses a relay inside of it instead of a triac will result in an outdoor light that doesn't blink and operates as expected.

5) Another option is actually to add a second LED bulb (or increase the bulb size...) while that may seem counter intuitive... it provides the leakage current that might be needed by the motion detector... and the LED driver is more likely to operating in a mode which doesn't turn on...   moving from a 40W bulb in the outside light to a 75W light is likely to change or stop the blinking rate.... 

Pure Energy has been installing LED bulbs for a while and have some experience with LED bulb brands and types, installation issues, customer acceptance, and bulbs that are the most successful with dimmer switches.  Pure Energy found LEDs are widely acceptable by customers, particularly because there is no mercury in the bulbs.  However, Pure Energy had to learn more about avoiding flickering, buzzing, and flashing when some LEDs are dimmed to the lowest setting on some dimmer switches. 

Issues with replacement light bulbs and dimmer switches as reported by Pure Energy:

  • Compatibility issues with pairing dimmer switches with the replacement light bulb, and
  • Trouble-shooting dimming issues such as flickering, buzzing, or flashing

 Suggested Procedure for Successful LED Installations:

 1.  On the Dimmer Switch manufacturer's specifications:  Check the dimmer switch specifications to see if it is compatible with the LED you want to install. 

 2.  Check the LED bulb manufacturer’s specifications to see if it is compatible with the dimmer switch. 

 3.  If there is no information that to confirm the compatibility, try the bulbs.  The installation is successful if they don't flicker, buzz, or flash.

 If an LED flickers, buzzes, or flashes:

Dimmer switches have a minimum load wattage required for the dimmer to work properly.  Sometimes, the total LED bulb wattage is lower than the minimum wattage required, and this can lead to the LED bulb flickering, buzzing, or flashing.

  •  In multi-bulb fixtures, remove one of the LEDs and put in a different LED, or
  • Adjust the dimmer switch settings.   For an example of how to do this, Search - Setting the Dimming Range on the dimmer switch.  Here is an example:  http://www.lutron.com/en-US/Products/Pages/StandAloneControls/C.Ldi...  where you will find info about setting adjustment dials

(The CREE is the one that causes us the most problem.  The Philips are the ones that are the most acceptable.)

We'd love some feedback about these practices and some suggestions for excellent LED bulbs.  Thanks, Tamasin


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