I put a led flood lamp with a movement sensor in the garden.

As far as I understand it has a light sensor and a motion i.e infrared sensor.

The latter only fires the light if the environment luminocity is less than the light sensor setting.

Someone told me that the motion sensor (I guess the IR in this case) will drastically reduce the lifespan of it because it the lifespand depends on the number of times it turns on and off.

All I can find on the web is that it depends on the number of hours that is on (and I'd add the power maybe).

Do you have any idea ?

  • Even if they are it's still better to run 13W instead of 60W, and anything is a better user experience than a CFL.
    – Mazura
    Commented Sep 3, 2022 at 18:16
  • The title is very confusing, as an LED has no sensor. Only a motion detection lamp has. In the end your question doesn't actually focus on the sensor but the number of on-off cycles, so you could point that out a bit better.
    – puck
    Commented Sep 4, 2022 at 8:52
  • @mahneh welcome to the site. The extremely simple answer is your friend was absolutely, completely, wrong. (It's very likely they were confusing the term "led" with some other totally unrelated term.)
    – Fattie
    Commented Sep 4, 2022 at 16:26

4 Answers 4


LEDs are the best choice for motion sensors

Someone told me that the motion sensor (I guess the IR in this case) will drastically reduce the lifespan of it because it the lifespan depends on the number of times it turns on and off.

Absolutely not. I know exactly what they're referring to*, and it's not LEDs at all. LEDs can be switched on/off thousands of times a second, in fact that is a prevalent method of LED dimming.

There is nothing in the electronic driver circuit that suffers from being turned on several times an hour. It's a non-issue with LEDs.

It is the first bulb type totally unaffected by starts.

So have fun with motion sensors and LEDs!

Build quality, on the other hand...

The threat to this unit's lifespan is being "cheap Cheese from overseas". Some years ago, Amazon opened their retail storefront to 3rd party sellers, and this happened (it's an ad, but it tells the truth). Except most of the 3rd party sellers are in fact the same few large corporations in a faraway country. As such, they are beyond the reach of domestic safety enforcement. Very tricky, Amazon!

Therefore it is our strongest recommendation to avoid buying electrical gear on Amazon (or obviously eBay, Banggood, DealExtreme, Wish.com, AliExpress, Newegg to some extent, etc. etc. But we hardly need to tell you that.) I don't care if your fidget spinner falls apart, but I do care if your motion sensor starts sparking inside due to faulty build and accelerates quickly into a big fire due to using cheap plastic instead of the costly fire-resistant plastic that is required by UL. This is one of the many things that UL checks when giving a UL Listing.

NEC (110.2) requires you use UL-listed equipment (or CSA or ETL equivalent).

* They're referring to a type of "arc discharge" light called a fluorescent. Most arc-discharge lights take 10 minutes to warm up (think street lights) but fluorescents can start in <1 second. The trade-off is "start"s take a toll on the bulb. On the cheap ballasts, you get about 10,000 starts, and that is the limiting factor on bulb life, so don't put them on motion sensors. With better ballasts you get 60,000 starts, so the motion sensor is no problem.

  • 1
    @MahNeh Fluorescents don't rely on conduction through a tungsten element. They have a gas tube and the electricity flows through the gas. Sort of like neon. en.wikipedia.org/wiki/Fluorescent_lamp I mean some fluorescents have a little tungsten filament at each end, but that's only a heating element used to pre-heat the bulb for a soft start (necessary to get 60,000 starts). Cheap ballasts ignore this feature. Commented Sep 2, 2022 at 19:34
  • I see, so the tunsgsten in the first case acts as a sort of resistance that heats up and emits as a black body radiation spectrum, sort of thing? in the other case Still I think both ends of the gas lamp always have a solid element that heats up? well in any case thanks for the insights.
    – Mah Neh
    Commented Sep 3, 2022 at 16:28
  • @MahNeh yes, true incandescent lights do what your first sentence says. The gas lamp just has electrodes on the ends, as you would expect. Many fluorescents make the electrode a filament also, solely for preheating. It shuts off after start. Commented Sep 3, 2022 at 19:07
  • Though turning an LED on and off wont in itself cause wear, repeated heating and cooling cycles could do (though to a far lesser extent than with florescent lights) Commented Sep 4, 2022 at 11:16
  • @Harper-ReinstateMonica thanks, i learnt a lot from your wisdom.
    – Mah Neh
    Commented Sep 4, 2022 at 19:01

LED lifetime is strictly hours (and current/temperature) based.

LED drivers are usually what fails first, particularly in cheaper units.

LED driver electronics are not particularly sensitive to being turned on - that's probably a misconception carried over from both incandescent and florescent bulb types, which are more limited in number of times they turn on as well as on-hours.

  • 2
    @manassehkatz-Moving2Codidact the question is whether the sensor - by turning the light on and off frequently - reduces the lifespan of the light. Commented Sep 2, 2022 at 14:45
  • Yes, that is exactly what I ask for. The reason is that 2 people told me that the lamps dont last more than 6 months (they say 17thousand hours in the package, so 6 months would not make sense) @user253751
    – Mah Neh
    Commented Sep 2, 2022 at 15:25
  • 4
    Keep your receipts and demand a replacement if your 17,000 hour claimed units fail in 6 months. Then again, 17,000 hours (roughly 2 years continuous) is horrible lifetime for an LED (50,000 hours is more like a decent/common number) so the bulbs may be low-quality.
    – Ecnerwal
    Commented Sep 2, 2022 at 15:29

I see no claims whatsoever in the Amazon listing that this meets any sort of National Testing Laboratory standards (UL in the US, or BSA (I think) in the UK). That right there should be a hint that this is a low quality device that's likely not going to last particularly long. Whether it's the LEDs themselves, the IR sensor, the LED driver or any other component, it's just probably not to last very long.

Since there doesn't appear to be any sort of officially recognized testing of this device, they can claim 1,700 hours, 17,000 hours, or 170,000 hours of life or whatever the marketing department demands, and there's nobody to hold them accountable to the claim. Failure within 6 months doesn't seem unreasonable.

In general, however, for LEDs, turning them on and off doesn't dramatically impact their life span as it does for incandescent or fluorescent bulbs.

  • Third party certification seems to be much less of a thing in the UK, than US based posters on this site make it out to be in the US. Many products even from reputable suppliers only have a CE mark and no third party certification, particularly if they are UK specific products (so looking at power supplies for example, the "soap on a rope" style ones that are sold worldwide will often have third party certifications while the wall warts which are UK specific don't bother. Commented Sep 3, 2022 at 17:48

Are you talking about the flood light itself, or the IR sensor?

As far as the IR sensor is concerned, I am not aware of any failure or wearout mechanism in an IR sensor (the diode part of an LED) based on the number of times it "turns on". That is, of course assuming that it's not overstressed in some way.

Same thing goes for the LEDs in the flood light itself. They do not wear out by being turned on and off. Look at the LEDs on the back of a LAN router. They are blinking continuously in response to Ethernet traffic, day in and day out. They do not fail.

  • The LEDs in a LAN router are very low-power LEDs. A floodlight includes not just LEDs themselves but also a driver circuit that could be affected by being turned on and off. Commented Sep 2, 2022 at 14:51
  • 2
    LEDs in general, @user253751, will, effectively, last forever. It's the driver circuitry, especially in low-cost Amazon special equipment that tends to fail.
    – FreeMan
    Commented Sep 2, 2022 at 15:02
  • Sure, anything is possible. But unless you've seen and analyzed the driver circuit, that statement is just speculative.
    – SteveSh
    Commented Sep 2, 2022 at 15:02
  • @FreeMan LEDs fail quite often when the cheapest ones are used and they are over-driven - like in cheap LED lighting. Commented Sep 2, 2022 at 15:06
  • 1
    @Criggie - Again, maybe. While not as complicated as the drive electronics for an LED motion sensing floodlight, old fashioned incandescent outdoor flood light with an IR motion sensor do have some amount of electronics in them. My dual flood above the garage doors has been up for around 8 years now with no problems. This is in an exposed location.
    – SteveSh
    Commented Sep 4, 2022 at 13:32

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.