Led house lights

[Sam Vimes]

I had reason today to look over the specification we wrote when planning to build our own house in 2009/10

We wanted LED lights throughout. GU10 7W -some dimmable, some not. At that time there wasn't much choice and the only option we came up with was from Philips. Each bulb cost £28 and some pennies. In the 15/16 years we have only had one bulb die and that was early in its life.

By comparison, today you can get a pack of 5 for less than half that price. The march of progress is quite illuminating at times.

 

[JTQ]

Much of technology has become relatively cheaper, more basic stuff like a beer or a decent meal out have gone completely the opposite way.

I also purchased additional LED bulbs this weekend. Here where and what you buy, major brand vs unknown affect what you pay though as you found, much cheaper than they were.

Have others noticed the massive drop in camping targeted solar panels compared to 2006?

 

[Woodentop]

For a start, LED bulbs are often quote as 25000 hours life. Indeed the LEDs will last that long or even much longer, but the electronics that drive the LEDs my expire in a very very much shorter time. If you want to see why, look at one of your bulbs that is switched on through the viewfinder of a digital camera (it usually doesn't show up on a mobile phone camera) and you will see that the LEDs are either flashing on and off sequentially (the LEDs in the bulb housing are mounted in a ring) or they all go on and off simultaneously.

As for dimming, don't go and pay stupid prices for 'dimmable' bulbs - you can do it much more easily.

Mains electricity actually is a sinusoidal waveform so it passes through zero twice for each cycle, so 100 times a second. The bulb filament however has a significantly long thermal lag so the element will glow for much longer than the waveform takes to do a cycle and thus to the human eye looks continuous. (The latency of the human eye will cause any continuously flashing light source shorter than about 1/12sec as continuous. This is why a TV screen looks like a steady picture when in fact the whole picture is being rebuilt once every 1/25th of a second.)

Thinking of dimmers driving such lamps, in the first half of the waveform if the electronic switch is switched on almost as soon as the waveform starts rising the filament will start to glow and eventually reach peak light output. However if the point at which the electronic switch turns on is delayed by a short time the amount of power getting to the filament in that first half cycle will be reduced (it will be on for less time) and the bulb will appear to be radiating less light, i.e. it is dimmed. Filament bulbs often used to pop off with such dimmers* as at the point that the electronic switch turns on the voltage supplied (instead of being a gentle rise from near zero) will go from 0V to say 100V or more in around 2uS generating a huge surge shock to the filament which fails. The electronics inside LED lamps don't like it up 'em either. (*Unless the dimmer always switches on at full and has to be turned down.)

The simple solution is to use a 'trailing edge' dimmer. This type of electronic switch is always on at the start of a half cycle but is switched off before the half cycle ends. The average power supplied to the lamp is thus reduced and it dims, but there is no possibility of a thermal shock. As an aside it also means that the dimmer radiates less electrical interference. Trailing edge dimmers are nowadays often the same price as a leading edge dimmer and are readily available from such as Toolstation and Screwfix.

Because the electricity supply is being switched off by the dimmer it will work with any type of lamp, LED or filament.

HTH