led lamps

[rumplestiltskin]

There are plenty of lamps around to replace 240v halogen recessed type lamps, and I see some to replace 12v halogen lamps. I was wondering if these led lamps work ok with a typical supply off a single transformer as I know sometimes a lighting transformer needs a minimum load. Especially when there is a transformer powering three 12 lamps, and if two lamps go dud, the third one sometimes is not enough to provide a suitable load for the transformer, so the third one goes out too. Just wondered if this is still how it goes and 12v led lamps are prone to problems like this? I am a bit behind the times with this so feel free to torpedo anything I've misunderstood.

 

[PrenticeBoyofDerry]

You fit LED drivers rather than transformers, they usually have minimum rating of zero to the maximum rating specified on the driver, which does vary.

 

[flameport]

For 12V halogens, it's usually easier and cheaper to remove the old transformers and fit GU10 lampholders instead.
Far more choice in GU10 LEDs.

 

[rumplestiltskin]

Aha! yeah that makes sense....there must be a lot of people getting home from the shop with their new 12 led lamps and they end up in a drawer

 

[eveares]

On a side note, how long have LED lamps been around that are on par with CFL's and Incandescents. I.E what was the development state of mains LED Lamps 7 Years ago.

 

[PrenticeBoyofDerry]

In the last seven years technology has moved on greatly, as have the specification regarding LED lighting and still continuing.
7 years nowhere near the standards they are now, in regards to efficiency to light output.

 

[ericmark]

We have a number of phrases used in the lighting industry which seem to be designed to confuse the public.

Toroidal transformer well does not need to be toroidal provides a percentage on input voltage, often these will work OK with LED lamps, but since the peak to peak voltage is higher than the RMS voltage it depends on what current limiting device is used inside the LED package.

Electronic transformer not really a transformer at all although they likely contain one, these regulate the RMS output far better than the toroidal transformer, but often have a lower limit, some will go down to zero, but because of the switch mode nature of the device the peak to peak voltage can be higher than the toroidal transformer.

Driver again confusing, it should refer to a current limiting device used to directly power a LED. However manufacturers seem to use the phrase to also describe a DC power supply, which is really not a driver but a smooth DC power supply. One has to read the description carefully.

Most LED bulbs have a driver of some type built into the bulb, this could be a simple resistor, or capacitor or a chip with a switch mode regulator. The latter often has a huge voltage range i.e. 10 ~ 36 volt or 150 ~ 250 volt, but the former is often very limited as to range. When I buy an LED bulb I really have not a clue if regulator is switch mode or simple capacitor or resistor and at 230 volt it is not really a problem. Yes the switch mode device uses less watts per lumen but they are all low power anyway.

I have 4 x 12 volt RMS lamps powered by a toroidal transformer the LED lamps worked for about 3 months then LED by LED failed. Had they blown in a week I would be sure it was the toroidal transformer but after 3 months hard to be sure. However not a single 230 volt LED has failed as yet so I would say convert 12 volt lamps to 230 volt.

 

[eveares]

but since the peak to peak voltage is higher than the RMS voltage

Well of course it is ; Vpp = (Vrsm x √2) * 2 right?

but because of the switch mode nature of the device the peak to peak voltage can be higher than the toroidal transformer.

So will I have trouble with this and this together?

 

[ban-all-sheds]

For 12V halogens, it's usually easier and cheaper to remove the old transformers and fit GU10 lampholders instead.

Always assuming that the luminaire is safe at that voltage, and has been tested by the manufacturer to prove that it is.

If you couldn't buy them, modify them and sell them as 230V items then you cannot tell people to modify them themselves.