Thread: low voltage light dimmers.

I've completely missed this thread as I often don't read electrical threads

The thread seems to be on the right track. Dimmed lights do use less power, but the perceived light output isn't directly proportional to the power used. The visible light output from a light globe isn't a linear relationship to power input. Also, I suspect our eyes don't have a linear relationship between perceived intensity and the actual light intensity (does this make any sense?).

What I'm trying to say is that halving the power to the light globe will probably make it look somewhat less than half intensity. And a light dimmed to half (perceived) intensity will probably use somewhat more than half power.

As an aside: There is a technique of manually synchronising generators before connecting them to the mains that use light bulbs (such as the "two-bright" and the "three-bright" techniques). they rely on the user determining the bulbs are the same brightness before closing a switch. Human eyes are very good at sensing small differences in brightness - and this difference often only corresponded to a couple of volts difference across the light bulbs. This is also possibly the reason why identical models of TVs in stores often look different.

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Originally Posted by Bleedin Thumb

Don't know if this is in the right section, couldn't find the DIY electrical section

Now that I have renovated several rooms of my modest abode I find that those trendy little low voltage downlights are actually naughty little energy suckers.

When I'm sitting in the lounge listening to some sweet soul music I like to have the lights turned lowwww just to get the mood happenin baby...

So the question on my lips is .......when you dim the lights are you using less power?
Is occasionally stumbling over the dog or yound child the cost of avoiding a guilt trip about destroying the planet?

mate dimmers definitley cut the power down on downlights but you have to make sure you use the right dimmers for the right tranformers 2 types leading edge and trailing edge dimmers for electronic and iron core trannys the dimmers also come in different va ratings also and some are very sensitive as to loading example 6 x 50w =300w or 300 va dimmer but i would suggest to use a 450 va dimmer as you are right on the borderline and will cook the dimmer in no time

mate there are a heap of different types on the market and from memory they are expensive! the brand i use to install was megaman seriously i think you should consider going for Led downlights for halogen relacements they only use 3 watts of power!.. ok they dont have the beam spread you get by using standars 50 w and the light output is not near the halogens but using 3 watts is better than 50 watts also example 1 x 50 w downlight uses 1x 50 watt tranny you can run 15 led lamps off the one transformer when purchasing beware there is some crap out on the market and yes they are as dear as poison also check some will operate on dc only some will operate on both ac/dc and most are not dimmable

I don't really care much about spread. I usually use the 28Deg bulbs as I like the spot effect of downlights so LED may be OK... except if you need to read a paper or a book.
Well that may be a bit of an exageration because I have never been in a house that is lit with LED's. I do have some of those OSRAM stick on LED lights that I use inside the pantry and even at less than 300mm above my spice jars I can hardly read a label.
I guess you can always keep the trusty Dolphin handy or a miners light strapped to your head....

And I forgot to set that ruddy meter up.

Don't worry Silent, these things take time... just like the renovations 7 years and only 3 rooms done, and none of them are completely finished!

Barchrist I sounded like my wife then!

I have always subscribed to the theory that less output means less current anyway, there are dimmable compact fluoros available Phillips distribute them I think and they come in a range of colour temps down to 2700k which is the same as an incandescent bulb. The are dimmable via a standard leading edge dimmer. The other methods of dimming fluoros requires some form of electronic lighting control system (LCS) like C-Bus for instance. The old way was using electronic dimmable ballasts capable of receiving a 1-10v signal from a LCS module. Newer protocols are probably becoming more popular like DSI (Digital Serial Interface) or DALI (Digital Addressable Lighting Interface) which also require specific ballasts.

Originally Posted by maxdangerous

If memory serves me right. The power consumption of your light circuits remain the same when you have them dimmed. A dimmer is just a resistive load placed in series with the lamp and as its resistance is increased so is the voltage drop across the dimmer and hence also across the lamp. Less voltage across the lamp equals less brightness but the current consumption is the same in all parts of the circuit...
It's been way too long since I went to bloody trade school

By the way, you can get flouro dimmers but they are a special type, some people have them fitted into the pelmets above curtains etc but I haven't seen anything like this for the compact flouro's

Nope - modern solid state dimmers are in fact small fast switches using thyristors and other clever bits to cut the current flow to the lights - so you do use less electricity. I have seen some figures on how much, but couldn't find them again when I went looking. The reduction is not linear so 25% dimmed does not give 25% saving.

You can get dimmable low energy (not low-voltage) CFs too, but they are costly.

New technology LED lights are the likely next low energy lights that will be dimmable, but they too are costly so a couple of years away.

I have replaced many 50w halogen downlights with 15w (60w equivalent) CF downlights and added additional switches to give better control - usually means running just one new wire to each new set to be switched.