Where do you get your LED lightbulbs from?

[scaryjim]

... First the voltage must be rectified from AC to DC. Now we need to step that voltage down. ...

Apologies for the pedantry, but you'll usually find the voltage is transformed down before rectification: it's far easier to step-down an AC supply than a DC supply

That said, I suspect you're right that it's the transformer that makes up the bulk of the extra cost: for LEDs I doubt you need a huge amount of smoothing of the supply, which means the recitfier is 4 diodes and a capacitor.

[Phage]

I've never tried LED bulbs before, what are they like? Do you notice any difference in the light quality?

Yes there is. The ones I bought are GU10 SMD replacements and tend to be bluer than the incandescents, even the ones marketed as 'warm'. However they would be perfect for the kitchen or bathroom, or places with hard to reach fittings like double-height ceilings where changing bulbs would be a real pain.

Oddly the bulb itself appears much brighter to actually look at, but the room seems slightly darker...I'm not sure why. I do get a buzz that I'm saving >45w on every one I replace !

[Zhaoman]

Yeah my main worry is LED bulbs not producing a full spectrum of colour so some colours may appear 'black' when being lit by them. I believe they have various techniques to boost the colours produced but I haven't really got a clue what the most of them are like. Once our flourescent lights go I'll be looking into getting them so hopefully they can produce a nice natural range of colours and be the standard bulbs by then! Nothing beats hands on experience of course so that's some really interesting insight Phage!

[davig019]

Apologies for the pedantry, but you'll usually find the voltage is transformed down before rectification: it's far easier to step-down an AC supply than a DC

Your quite right, considering a transformer uses magnetic fields generated by AC current in the primary coil I don't even know how that would work on DC apart from making heat :l For DC just use a voltage divider but much less efficient than AC as you said. And I'm supposed to have got an A* in electronics and an A in physics...

[BerZerk]

You can find plenty of LED bulbs from dealextreme.com. They send it from China/HK. But I don't really have any problem with them.

ps. Switch mode psu (I'm suspected they used this in the LED bulbs) is getting more advance now. Anyone seen the size of a small cube 5V 1A USB charger for the Apple?!.

hxxp://www.dealextreme.com/p/usb-power-adapter-charger-orange-us-plug-100-240v-129498

[Sputnik]

Apologies for the pedantry, but you'll usually find the voltage is transformed down before rectification: it's far easier to step-down an AC supply than a DC supply

That was the norm for a long time, Using big 50Hz capable transformers made of lots of copper, Then sticking the reduced AC through a bridge rectifier and adding a bit of smoothing via some large electrolytic caps.

But, With switched mode power supplies the mains goes through a bridge rectifier first and then a high frequency waveform is created which is fed into a tiny little transformer.

[peterb]

That was the norm for a long time, Using big 50Hz capable transformers made of lots of copper, Then sticking the reduced AC through a bridge rectifier and adding a bit of smoothing via some large electrolytic caps.

But, With switched mode power supplies the mains goes through a bridge rectifier first and then a high frequency waveform is created which is fed into a tiny little transformer.

As he says - and the other advantage is that the output filter ('smoothing' capacitors) can be much smaller as lower value capacitors are needs because the residual ripple is much lower. Voltage regulation is also easier, and usually achieved by controlling the duty cycle of the mains inverter on the input side of the step down transformer - again more efficient.

[scaryjim]

Ah, learn something new every day Been a long time since I did any physics.

I've just got a new CPC (http://cpc.farnell.com) catalogue through and they look to have some decent prices on LED bulbs at the minute, including some good savings for bulk purchases as low as 5 items (which is obviously great if you've got multiple 4-bulb fittings to replace, like I have ).