low voltage light dimmers.

[Bleedin Thumb]

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

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.:o :doh:

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?

[silentC]

It's a good question. My sparky says yes. I have a meter here, I'll hook it up over the weekend and see what happens.

I also watched Carbon Cops on the ABC the other night and they had these low energy fluro globes for downlights. Supposed to use a bit over half the power of a 50w halogen. Not sure of the cost or if they're available for 12v.

[Bleedin Thumb]

Hi Silent,
The trouble with the compact flouros is that you can't dim them and its hard to get funky under the white glare that flouros give off.

The low energy flouros that you mentioned may be different from the compacts but I don't think that they could be dimmed as they don't have a filement.

Any how it will be interesting to so what results the meter gives.
Cheers.

[maxdangerous]

Stay away from the cheaper units as well as the transformers they use to step down the voltage tend to humm... I'm guessing this would mess with the serenity of the moment too.
Cheers
Max

[silentC]

The trouble with the compact flouros is that you can't dim them
Good point. I was thinking of getting a few more dimmers in, as we have 6 banks of 4 downlights in the place but only two have dimmers, so when they're on, they're on and it's 200 watt hours every hour (quick calculation: 3 cents per hour per bank of 4).

So if dimmers are about $20 each and I dim all the lights 50%, then it will take about 1300 hours to pay them off. Now that's a lot of getting funky!

[Bleedin Thumb]

I have been giving this subject a bit of thought lately .... senility perhaps.. but I recon that I usually have the lounge room lights set at below 25% of their brightness... I don't know if that equates to less than 25% of their power consumption.

When you conect your meter up Silent make some incremental adjustments and see what results you get.

If it is the case you may be able to justify their existence if you have them dimmed low, or is it the transformer that chewing the juice?

Questions, questions, questions....

[silentC]

I usually have the lounge room lights set at below 25% of their brightness
Ditto

I don't know if that equates to less than 25% of their power consumption.
I think that the transformer loses a bit of energy in the form of heat. Not sure about the dimmers. My sparky reckons the lights use less power when dimmed (that seems logical) but couldn't say whether it was proportional to the amount of light being emitted.

The meter I have is an old analogue meter and I time the rotor with the stopwatch then extrapolate out to kWh. It's a bit rudimentary but I should be able to spot a difference if there is one.

The biggest hassle is getting up in the ceiling and hooking the lights up to a powerboard so I can insert the meter.

[Bleedin Thumb]

Sorry Silent that does sound like a big hassle...so just think of it as an advancement of science. Increasing our awareness and understanding of global warming issues.

There probably isn't a Nobel prize in this one but you may get a warm fuzzy feeling somewhere.:D ..Also as you have done a lot of your own wiring I hope that is the only feeling you get crawling around in your ceiling!!!

Cheers:2tsup:

[silentC]

When I finished installing the flue for the fire I said "right, that's the last time I'm getting up there for a while".

Bloody science... :~

[craigb]

Well it's a compromise for sure. In our recent reno we put compact fluro's in the kitchen where the lights are on a lot and dimmable low voltage lights in the dining room.

Also made a point of buying the top of the line electronic transformer. So hopefully the combo of a good transformer and the dimmed lights helps.

The trouble is the quality of fluro light is not the greatest. The light people we spoke to said that dimmable compact fluro's should be on the market "soon". :wink:

I'll be intersted to see your test results too.

[witch1]

i have not done any scientific stuff to prove this but from my observations on my home downlights they do not make much improvement in the power bill.
i think you will find that the heat generated by these lamps and dissipated to ambient atmosphere would account for a lot of the wasted power, compared to the fluoro type lamps.
further, i am sure i have seen dimmable fluoro's somewhere in my travels around the hardware departments
i have found a considerable saving in power bills since converting to fluoro lamps, (not dimmable) difficult to quantify in figures as we have had a lot of variables in the equation over the years, but certainly the bills are now lower.
hope this helps.
joe

[OBBob]

Hi There

My father is an electronics engineer and says the answer is yes. He has just replaced all his down lights with 25w globes instead of the 50s ... there were tooo many installed as it was. By doing this and replacing all teh normal globes with CFs he calculates hge has reduced the consumption to 25% of what it was. Of course there are some losses and your lights are probably negligable compared to some other appliances ... every bit helps though!!

[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:doh:

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

[silentC]

Not an expert but doesn't Ohm's law state that current = volts / resistance, so if resistance increases and volts remains constant, current will decrease?

http://en.wikipedia.org/wiki/Electrical_resistance

[silentC]

But I've just found out that they don't work by adjusting the resistive load, they work by switching off and on:


Solid-state light dimmers work by varying the "duty cycle" (on/off time) of the full AC voltage that is applied to the lights being controlled. For example, if the voltage is applied for only half of each AC cycle, the light bulb will appear to be much less bright than when it get the full AC voltage, because it get's less power to heat the filament. Solid-state dimmers use the brightness knob setting to determine at what point in each voltage cycle to switch the light on and off.

Typical light dimmers are built using thyristors and the exact time when the thyristor is triggered relative to the zero crossings of the AC power is used to determine the power level. When the the thyristor is triggered it keeps conducting until the current passing though it goes to zero (exactly at the next zero crossing if the load is purely resistive, like light bulb). By changing the phase at which you trigger the triac you change the duty cycle and therefore the brightness of the light.

[maxdangerous]

Told you it had been a long time... now I'm trying to remember how total impedence comes into it... loads connected as rheostats, inductive and capacitve reactance aagggggggggghhhhhhhh:o :o :o

[maxdangerous]

Now I feel like I'm back at work, someone has just started talking all dirty about sine waves and thyristor trigger points.......:o
I'm gunna go and find some nice friendly splinters to play with

[SilentButDeadly]

I changed out the 12V downlights when we moved into our house. Four in the bedroom, four in the kitchen, all had 50 watt globes.......changed them all to 240V GU10 downlights (exactly the same size as the 12V). They look like this
http://www.cromptonlighting.com/catb/products/8cfannx9v.jpg

Used four warm white 7 watt Megaman compact flurescent downlight globes in the bedroom. Slowish to come to full brightness but fine for this room - saved about 220 watts I reckon.
They look like this
http://www.megaman.cc/var/images/global/products/products/c1/s4/br0407.jpg

In the kitchen, we are using two 11watt Megaman CF lights and two 35 watt halogen globes that have the same output as a 50watt. The halogens go over the critical work areas while the CF's are more general because they are slower to light and have a much wider light beam. Although you can get reflectors (different light fitting) that help focus that broad CFL beam down tight to 50 degrees (same as the halogen).

And there are dimmable CFL downlights these days. However, they are expensive and the dimming action is step-wise. I think there are four steps between zero and flat out.

If I were building/renovating (which I am) then I'd switch to the PL/PLC form of compact fluro light in the work areas http://www.cromptonlighting.com/cat/show_fittings.php?subcat=6&id=1# the fitting are more expensive but the light is good (just like normal fluro) and the globes are cheap.

[OBBob]

Yep ... depends on if you use the old style transformers or the new mini switchmode tx's.

[Bleedin Thumb]

Hi SBD thanks for all the info, those 240V GU10's what wattage are they?

[SilentButDeadly]

Typically, the 240V halogens can be had in 35W and 50W.....there are typically two versions of the 50W - one which has the same light output as the 35W and another with high light output. http://www.cromptonlighting.com/catb/show_lamps.php?subcat=31&rowstart=6&page=2&id=#

The Megaman CFLs can be had in 7W, 9W and 11W, each with three different colour temperatures (coolwhite, daylight and warmwhite)....no idea what the lumen output is!

[silentC]

So all the new gear is 240v? You'd need new fittings as well then, obviously not just a matter of switching globes. 12v Halogens are about $20 ea. with the transformer. How does that compare to what you put in?

[SilentButDeadly]

So all the new gear is 240v? You'd need new fittings as well then, obviously not just a matter of switching globes. 12v Halogens are about $20 ea. with the transformer. How does that compare to what you put in?

$9 for the 240V fitting http://www.neco.com.au/product.asp?pID=94&cID=10, $23 for the Megaman GU10 CFL globe http://www.neco.com.au/product.asp?pID=168&cID=47 or $4 for the GU10 halogen globe http://lightingpro.com.au/catalog/product_info.php?products_id=38&osCsid=d9853e5041e036a2527cec3432f97d4d

There is a really good article about this very topic in the latest Jul-Sep 2007 issue of ReNew Magazine pp20-23 www.ata.org.au (http://www.ata.org.au)

[silentC]

Thanks. Looks like you can just buy the adapter as well, it will probably work with the existing housing that I've got. http://www.neco.com.au/product.asp?pID=139

Might get a couple and try them out.

[Dan]

I've heard that Halogen lamps don't like running at less than full brightness. This bloke offers a fairly good explanation as to why.
http://members.misty.com/don/bulb1.html

[Dan]

Another way to get the "mood" right could be to use a couple of floor standing "up" lights. Just the basic model without an inbuilt dimmer, chuck in a 5w warm white CFL's and you're done (works for me anyway).

[SilentButDeadly]

Thanks. Looks like you can just buy the adapter as well, it will probably work with the existing housing that I've got. http://www.neco.com.au/product.asp?pID=139

Might get a couple and try them out.

Yeah you can.....but the adapter costs more than the entire fitting. And it is the same thing that's in the new fitting:doh: So you're better off buying the entire fitting, removing the wiring bit and tossing the alloy in the recycling if all you want is the wiring :o

The 12V and the 240V fittings themselves are EXACTLY the same. The alloy bits I mean.

And your local lighting shop will have them so you don't have to buy over the internet if don't want to.

If you have a fixed 12V downlight then just grab a fixed 240V downlight, same goes for the gimbal version.

Just make sure you don't have a gimbal version and try and replace it with a fixed version. The holes in your ceiling will be a different size. I know this from experience..:C ...however, I managed to make a series of bastard versions (based on old and new) that looks just fine

[silentC]

They show the prices as $8.95 for the whole thing and $7.95 for the adaptor, unless I'm missing something.

But for $1 difference, I might as well buy the whole thing and sell the 12v ones with the transformers at a garage sale.

[Ruddigar]

But for $1 difference, I might as well buy the whole thing and sell the 12v ones with the transformers at a garage sale.

I'll give you 50c each for the lot. :p

[silentC]

Yeah OK but there's a 4000% buyer's premium attached to this sale :p

[Ruddigar]

I fold. :(

[chrisp]

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

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.

[ptrott]

REWARD OFFERED!!!! For the capture of Hopalong Capacity. He escaped from a secondary cell early yesterday and has been at charge for about 24 amp hours.
He is wanted in connection to the induction of a 14 year old coil who was found
2 days ago, burnt out and as crisp as a microchip.
Hopalong was last seen riding a kilocycle around an oscilliatory circuit and is believed to be armed with an electron gun. Do not aproach as he is likely to discharge violently.
The charges were laid under OHMS LAW.

[patty]

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

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.:o :doh:

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?

[patty]

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

[patty]

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

[Bleedin Thumb]

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....

[silentC]

And I forgot to set that ruddy meter up. :~

[Bleedin Thumb]

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!

[TheDocta]

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.

[Bloss]

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:doh:

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.