LIVARNO LUX spotlight for sale at LIDL supermarkets from 09/14/17 (with inherent design flaw!)
Posted: September 7th, 2017, 10:15 pm
I've just noticed that LIDL supermarkets will be selling some outside spotlights, for lighting up an area outside.
These type of lights are ideal for front gardens, rear gardens, outside garages, for use as security lights, or any large area that needs illumination.
This is the light here: https://www.lidl.co.uk/en/Non-Food-Offe ... cleId=6102
It is only £11.99, which is not that bad, but there's a bit of a catch.
These lights have PIR motion detectors, which are great for short, controlled bursts of light with an appropriate type of bulb. It means that, as soon as motion is detected (for example, people walking into the area), the light is switched on to provide the correct illumination. The amount of time the light remains on for, is controlled by the settings on the light, and can be adjusted between 1 and 15 minutes per time. Great with an LED as it gives a good amount of controlled light for the area.
Here's the big catch: the light supplied is rated 23W, so obviously isn't LED. The page doesn't suggest LED in any way, but it does say "energy saving". Therefore, with the wattage and info supplied, it has to be CFL - i.e. the weird looking twisty bulbs that were used before LEDs made it big.
CFL bulbs have a rated lifespan of 10,000 hours - about 1/3rd of the lifespan of LEDs. But, and this is a big but, the lifespan of CFLs (and any fluorescent light come to that) is heavily dependent on the amount of on/off cycles that the bulb experiences. On average, CFs (and other fluoros) tend to conk out around the 3,000-3,500 on/off cycles. This gives them their 10000 hour rating (based on 3 hours a day).
Even if the above explanation was your first insight into how CFLs/Fluoro's work (you can read more about their working, and EOL signs on Wikipedia) then you'll realize that pairing a CF with a PIR motion sensor is just about the worst thing you can do. CFs like to be left on, yet PIRs switch the light on and off every time there is movement.
To give you an idea on how bad this is in reality, here's a best case, and worst case scenario. Remember, CF's are supposed to last 10,000 hours - for comparison sake, an LED will last 30,000 hours (regardless of switching cycles) and incandescent/halogen lights are rated 1,000-2,000 hours (regardless of switching cycles).
Best Case (based on switching frequency of 15 minutes with 3,500 on/off cycles):
15 minutes per cycle / 60 minutes per hour = 0.25 hours per switching cycle
0.25h * 3500 on/off starts = 875 hour bulb lifespan (in real world scenario, will be closer to 800 hours)
Worst Case (based on switching frequency of 1 minute, at 3,000 on/off cycles):
1 minutes per cycle / 60 minutes per hour = 0.016666 hours per switching cycle
Multiplying this recurring decimal by 3000 cycles gives you.... drum roll please.... 50 hours bulb lifespan.
What an absolute disaster that is...
In fact, to see why it is a disaster, let's compare those calculations with the rated lifespan at 3hrs/cycle (10,000 hours).
At 800 hours (best case scenario), the light bulb is being used for 8% of what it was designed for.
However...
At 50 hours (worst case scenario), the light bulb is being used for just 0.5% of what it was designed to be.
That means that 99.5% of the working hours of the bulb were lost by the high frequency of on/off cycles.
And that's how switching on/off a CFL, or fluorescent bulb, will dramatically affect its operating hours.
This is why you should NOT pair a CFL bulb (or any bulb whose lifespan is dependent on switching cycles) with a PIR senor (or any other sensor that switches on/off rapidly).
A photocell, like what is found on streetlights, would be way better as it would keep the area illuminated for a long time and therefore keep the integrity of the bulb for way longer (and possibly even more than its 10,000 hour rating).
Apart from that inherent design flaw, though, they look like good fittings - therefore, if I was going to buy one of those, I'd be very tempted to either take the CFL out, and put in an LED (or even an incandescent or halogen, as they'd both fare up better than the CF, see calculations above) - or otherwise, disconnect the PIR sensor so that the CFL was permanently illuminated whenever power was applied to the fitting.
Note: those lights also come with a 3 year warranty... I'd be tempted to use one, then take it back after 50 hours of use and complain that the bulb crapped out on me - which, if used on the lowest setting, at 1 minute intervals, would actually happen.
These type of lights are ideal for front gardens, rear gardens, outside garages, for use as security lights, or any large area that needs illumination.
This is the light here: https://www.lidl.co.uk/en/Non-Food-Offe ... cleId=6102
It is only £11.99, which is not that bad, but there's a bit of a catch.
These lights have PIR motion detectors, which are great for short, controlled bursts of light with an appropriate type of bulb. It means that, as soon as motion is detected (for example, people walking into the area), the light is switched on to provide the correct illumination. The amount of time the light remains on for, is controlled by the settings on the light, and can be adjusted between 1 and 15 minutes per time. Great with an LED as it gives a good amount of controlled light for the area.
Here's the big catch: the light supplied is rated 23W, so obviously isn't LED. The page doesn't suggest LED in any way, but it does say "energy saving". Therefore, with the wattage and info supplied, it has to be CFL - i.e. the weird looking twisty bulbs that were used before LEDs made it big.
CFL bulbs have a rated lifespan of 10,000 hours - about 1/3rd of the lifespan of LEDs. But, and this is a big but, the lifespan of CFLs (and any fluorescent light come to that) is heavily dependent on the amount of on/off cycles that the bulb experiences. On average, CFs (and other fluoros) tend to conk out around the 3,000-3,500 on/off cycles. This gives them their 10000 hour rating (based on 3 hours a day).
Even if the above explanation was your first insight into how CFLs/Fluoro's work (you can read more about their working, and EOL signs on Wikipedia) then you'll realize that pairing a CF with a PIR motion sensor is just about the worst thing you can do. CFs like to be left on, yet PIRs switch the light on and off every time there is movement.
To give you an idea on how bad this is in reality, here's a best case, and worst case scenario. Remember, CF's are supposed to last 10,000 hours - for comparison sake, an LED will last 30,000 hours (regardless of switching cycles) and incandescent/halogen lights are rated 1,000-2,000 hours (regardless of switching cycles).
Best Case (based on switching frequency of 15 minutes with 3,500 on/off cycles):
15 minutes per cycle / 60 minutes per hour = 0.25 hours per switching cycle
0.25h * 3500 on/off starts = 875 hour bulb lifespan (in real world scenario, will be closer to 800 hours)
Worst Case (based on switching frequency of 1 minute, at 3,000 on/off cycles):
1 minutes per cycle / 60 minutes per hour = 0.016666 hours per switching cycle
Multiplying this recurring decimal by 3000 cycles gives you.... drum roll please.... 50 hours bulb lifespan.
What an absolute disaster that is...
In fact, to see why it is a disaster, let's compare those calculations with the rated lifespan at 3hrs/cycle (10,000 hours).
At 800 hours (best case scenario), the light bulb is being used for 8% of what it was designed for.
However...
At 50 hours (worst case scenario), the light bulb is being used for just 0.5% of what it was designed to be.
That means that 99.5% of the working hours of the bulb were lost by the high frequency of on/off cycles.
And that's how switching on/off a CFL, or fluorescent bulb, will dramatically affect its operating hours.
This is why you should NOT pair a CFL bulb (or any bulb whose lifespan is dependent on switching cycles) with a PIR senor (or any other sensor that switches on/off rapidly).
A photocell, like what is found on streetlights, would be way better as it would keep the area illuminated for a long time and therefore keep the integrity of the bulb for way longer (and possibly even more than its 10,000 hour rating).
Apart from that inherent design flaw, though, they look like good fittings - therefore, if I was going to buy one of those, I'd be very tempted to either take the CFL out, and put in an LED (or even an incandescent or halogen, as they'd both fare up better than the CF, see calculations above) - or otherwise, disconnect the PIR sensor so that the CFL was permanently illuminated whenever power was applied to the fitting.
Note: those lights also come with a 3 year warranty... I'd be tempted to use one, then take it back after 50 hours of use and complain that the bulb crapped out on me - which, if used on the lowest setting, at 1 minute intervals, would actually happen.