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Less Voltage when Dimming

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SNG

New Member
Hi... I am busy with renovating my bathroom. Did read a few times when you dim the lights with 10-20%, you can save some energy. I do have halogen lights above my mirror, my bath tube and a third unit is mounted above the shower head (all waterproof of course).

Do I save more energy when I put a dimmer between the main power line and the trafo of the halogen lighting or is it better to do between the trafo and the halogen bulb? The main reason to use a dimmer is to save some energy without losing in comfort... (don't want use CFL bulbs, love the halogen lighting effect).
 

SNG

New Member
Start here
The Great Internet Light Bulb Book, Part I
Search for Use of Halogen Bulbs with Dimmers
Nice article to read but can't find anything what explains which dimming is the best way, before or after the trafo. Can understand that dimming is not so good for a halogen but in my other bathroom I have 3 sets of halogen running for 4 years now without one bulb broke. I dim these lights on the socket.

When I dim the halogen on the 12V line, will have that infect on the trafo and the main power line? Will it use then less voltage? Or is it better to dim from the socket as I do in my other bathroom? Low voltage dimming is much easier and when I dim on the socket, I have to use a triac.

Question is also for when using LED lighting. That will save energy too and they lost a long time. You have 2 types of LED bulbs, 240V screw in and 12V. If I want dim these LED lights, where can I best do my dimming to save most of the energy.....at 220V or 12V ?
 
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Hero999

Banned
You're better off turning some lighs off than dimming them.

The cooler the filament is the less efficient it is so it makes sense to operate it at as higher temperature as possible.

Also dimming isn't good for halogens as it can actually shorten their life.
 

dknguyen

Well-Known Member
Most Helpful Member
We use halogens everywhere in the house...except the bathrooms. We used to use them, but they kept dying. I suspect it's because the water vapour was having a cooling effect on the bulbs shortening their lifespan (I think halogens depend on some redeposition of vapourized filament metal back onto the filament which requires high temperatures).
 
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SNG

New Member
@dknguyen - We use for that reason halogen lighting in a waterproof housing.... It runs for 4 years in one of our bathrooms and not one single bulb has been broke since... We use halogen lighting everywhere in my house and in the kitchen where we in the beginning didn't use any dimmer, I needed to replace the bulbs each couple of months. After we started to use a dimmer in the kitchen too, not one bulb has been changed anymore....

@Hero999 - You can also better turn your computer right now off to save more energy :)

Only what I like to know what is best way to dim low voltage lighting.
 
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Hero999

Banned

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Hero999

Banned
I was 99.99% sure it was you and going by the way you've responded I'm 100% sure.

It should have been obvious that I was trying to help you.

Please ask yourself this question before giving out negative reputation: "Is this person really being nasty?" If the answer is no then do not click on the negative reputation button!

I shall try to resolve this over PM.
 

Sceadwian

Banned
SNG already got bad rep from me for their posts so far. There's no reason to ever respond in the manner he has so far.
 

SNG

New Member
Come on, stop talking about it and go on with posting about electronics.
Who cares about these reputation points... your knowledge and kindness is what counts and not some stupid reputation game... as a new poster to this forum I even don't know what that reputation thing does... and I even didn't know that clicking by that function it will cost Hero999 points....

if anyone has comments about this, please contact me in private, this kind of discussions don't belong in public... very simple forum ethics.... this is also what I wrote in a posting before but deleted by myself to get this absurd discussion stopped!!

so does anyone know what is the best way to dim a halogen or LED lighting... at the socket or at low voltage... :rolleyes:
 

Sceadwian

Banned
I don't know much about the conversion process for low voltage lightning but I'm assuming it's just a transformer and a bridge rectifier, in which case the simplest way would be at the socket. You could also PWM the low voltage side with a mosfet as well, either way works, efficiency is going to be up to the circuit your build not either method being more efficient.
 

SNG

New Member
yeh was expecting that the socket will be easier too... my current setup is a dimmer between the main lines and the socket... the main reason was when I turned the dimmer on the off position, the trafo will not get any power anymore... when I dim on the low voltage it will still require power to run the trafo... asked my contractor too what is the best solution and he said on the low voltage line as most lightning is created on that way... don't believe that because the trafo is then still running and consuming electricity...

gonna make a test setup to test out both setups and measure which solution saves the most energy and let it run for a couple of weeks...
 

Sceadwian

Banned
I'm assuming by trafo you mean transformer? Don't suppose you could use slightly less confusing words =)
I think you're massively over analyzing it. If you're really worried about efficient lightning you should be using fluorescent lightning, they do make ballasts that can dim now.
 

SNG

New Member
yeh it is indeed a transformer... different parts of the world using different words :)

Reason to be more efficient is that we're getting of the grid and installing some solar panels on our roof... each watt then counts.

Problem is that I can't use fluorescent lighting. My wife is very sensitive to fluorescent lighting and she get immediately a headache of it. In our offices and houses you will find not one fluorescent bulb anymore. Lot of people have the same kind of problems and even don't realize that it can be the source of their migraines. Since we have ban the fluorescent out, her migraines are much less :)

I also don't like the effect of it, you can't have a nice strong beam with it. One serious alternative I am serious considering is LED lighting. More efficient then halogen or fluorescent and still a nice nice beam of light.
 

Hero999

Banned
Seriously, I know I've said this before but don't dim the halogens if you can avoid it. If you want to reduce the light intensity then have several banks of lower wattage bulbs and switch some of them off if it's too bright.

As far as I'm aware, fluorescent lighting is only a problem if low frequency magnetic ballasts are used. Some people are susceptible to the 100/120Hz flicker. High frequency switched mode ballasts use a frequency of 20kHz to 200kHz which is far too high to give anybody any problems.

LEDs are not more efficient than halogens, it's a myth. At best LEDs offer similar efficiencies to fluorescents, under most conditions they're slightly worse. The only time LEDs are actually better is when you want a direct light source and a fluorescents would require a lossy reflector to be fitted.

Having said this, LEDs are an excellent choice for your application. Going from what you've said, you want a direct light source which already rules out fluorescents so LEDs are the perfect choice and are easily dimmed.

Going back to the original question: how ydo you dim low voltage lighting?

Most mains dimmers, you buy off the shelf, will only work from 240/120V AC 50/60Hz. They will not work from 12VAC and most also have some sort of minimum wattage requirement. Lots of them will also not dim halogen lighting. Given this, you need to put the dimmer before the transformer, not after it, unless you want to build your own special dimmer circuit that will work from 12VAC.

If you're going to power this from a solar panel and not have it connected to the grid at all then I'd recommend switching to DC for all the lighting. This means that you won't have any lossy inverters to worry about.

If you go for LEDs then you can buy dimmer modules for them, the disadvantage is that LED lighting in general is a lot more expensive than incandescent and the dimmers tend to be proprietary and only compatible with the products from the same manufacturer. If you're knowledgeable enough then you can build your own LED lighting fixtures and dimmer which might save you a bit but not much.
 
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SNG

New Member
Thanks for your deeper explanation, really appreciate it :)

Have created a few test setups in my companies lab and let run it for a couple of weeks. Use a normal incandescent bulb, halogen, fluoroscent and led lighting. All with an automatic dimmers which turns each device on and off, dimmed and so on. With this program we can simulate 6 months use within 1 month. Each light source has an independent energy meter so after a month we can pretty say which one is the best one to use for us. The second setup has a led and halogen light and connected each to a small solar panel, also again connected to the computer to simulate heavy usage and an energy meter...

will post the results here when we have conclude the data...
 

tcmtech

Banned
Most Helpful Member
As far as I know Halogens are simply brighter because of the halogen gasses used in the light. They allow the filament to be ran hotter. Dimming a halogen even slightly drops the filament temperature back to the level of a common incandescent bulb.

Buy an incandescent bulb and use that. Just think of it as a factory made pre dimmed halogen! ;)
Dim is simply less lumen's output. Less lumen's comes from less power input. Why dim a 100 watt halogen down to the output of a 60 watt bulb when you can just by a 60 watt bulb and save yourself a load of time effort and money?
Get a light meter and do an honest test of brightness. I bet the smaller bulb at normal power puts out the same light as the bigger light that is dimmed to its same level of brightness.
;)
I go through energy savings arguments about every two weeks with someone who read something on the Internet and either believed it was true or simply misread the information or most often flat out did not understand it! :mad:

I have an associate that I did a home energy use audit for. I had him change out all of the lights he had from standard to CFL's.
It cut his KWh usage by around 25% in the first month. :)
I was at his place some months later to do another one. His bill doubled for unknown reasons.
He read or heard some place halogens were more efficient than CFL's So he switched his whole house over to them.
I asked him why. He said they give off more light and are more efficient than regular bulbs.
I told him yes they are more efficient than regular bulbs but going by lumen's per watt they are about 4 times less efficient than CFL's. I showed him the numbers on the boxes.
He said but the lumen output ratings are higher than the CFL's!
Well of course they are! They use far more wattage than the CFL's do.

The watt meter just measures wattage and could care less about what type of load you have.
Now he is back to CFL's again.
 

Hero999

Banned

Sceadwian

Banned
Hero, maybe older white LED's no modern ones.
According to Wikipedia Halogens give 10-30 lumens per watt.
Fluorescents are 60-70 lumens per watt
Philips and Cree both have LED's out that are supposed to be over 100 lumens per watt. It's just a matter of time for the factors that produce them to make them in large enough numbers and cheap enough to take over.
 

Hero999

Banned
Yes, LEDs have been more efficient than halogens for years.

Was the LED white or was it green?

It wouldn't surprise me if it was green because the eye is more responsive to green so it's easier to achieve a higher lum/W. I hope it was white because if it was green it wouldn't be a fair comparason.

You're probably right that they will soon me more efficient than fluorescents. I can't wait until they are. I don't like fluorescents because of their poor light quality.
 
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