Halogen 12-Volt DC Lighting

[Ravenvalor]

Hello,

Does anyone know of a source of high quality halogen 12-volt DC lighting?
I have been looking at the various lighting sources: Amazon, Kichler, Platt, but cannot seem to be able to locate DC. The reason that I am looking is because I would like to try some halogen DC lighting in my home just for curiosity purposes.

Thanks for the help.

 

[gar]

211106-0854 EDT

Why DC and not AC?

,

 

[Ravenvalor]

211106-0854 EDT

Why DC and not AC?

,

Thanks for the help.

DC has no flicker.

 

[Besoeker3]

Thanks for the help.

DC has no flicker.

We have 12V 50W GU10 halogen lights in our bathroom. I don't notice any flicker with 50Hz ac. Or with 60Hz.

 

[ActionDave]

It would be easy to install a bridge rectifier on the 12V side of a transformer and make your own DC.

 

[synchro]

It would be easy to install a bridge rectifier on the 12V side of a transformer and make your own DC.

I think you'd also have to add a filter capacitor to reduce the ripple and hence any flicker it may cause. Otherwise the instantaneous power drawn by a lamp filament from rectified AC would be the same as that using AC directly from the transformer (ignoring the forward voltage drop across the diodes).

 

[gar]

211106-2047 EDT

Ravenvalor:

If you consider an ordinary tungsten filament bulb, and excite with the same power input ( meaning same filament temperature and light output ),
then compare lamp life between DC power and AC 60 Hz you will likely find life at DC to be possible 1/10 that at 60 Hz.

Now change to a halogen bulb that will run at a higher filament temperature, has a brighter output, when operating at its nominal voltage, and compare its life with an ordinary filament and ordinary gas ( likely nitrogen ) in the bulb, and you may find a longer life even though brighter. Reduce the input voltage so the bulb runs cooler, and you will loose that increased life. The reason is that the internal temperature is not high enough to cause redistribution of tungsten back on the filament. I can not tell you how much difference there is in life of a halogen bulb between AC and DC when operated at is nominal voltage.

If you take an incandescent and operate at 60 Hz, and look at its output with a fast enough photo detector, then you will see a small 120 Hz modulation of the light intensity. Not a hard experiment to run.

.

 

[Ravenvalor]

211106-2047 EDT

Ravenvalor:

If you consider an ordinary tungsten filament bulb, and excite with the same power input ( meaning same filament temperature and light output ),
then compare lamp life between DC power and AC 60 Hz you will likely find life at DC to be possible 1/10 that at 60 Hz.

Now change to a halogen bulb that will run at a higher filament temperature, has a brighter output, when operating at its nominal voltage, and compare its life with an ordinary filament and ordinary gas ( likely nitrogen ) in the bulb, and you may find a longer life even though brighter. Reduce the input voltage so the bulb runs cooler, and you will loose that increased life. The reason is that the internal temperature is not high enough to cause redistribution of tungsten back on the filament. I can not tell you how much difference there is in life of a halogen bulb between AC and DC when operated at is nominal voltage.

If you take an incandescent and operate at 60 Hz, and look at its output with a fast enough photo detector, then you will see a small 120 Hz modulation of the light intensity. Not a hard experiment to run.

.

Yes, A lot of design goes into that lamp shape in order to keep the filament nice and hot

About the 120Hz modulation, does it drop all the way down to zero light intensity or close to zero?

 

[AdrianWint]

About the 120Hz modulation, does it drop all the way down to zero light intensity or close to zero?

The current drops to zero but the light intensity will not. The filament can't cool down fast enough before it gets re-heated on the next half cycle. As Gar said, it you looked at it with a fast enough camera, would see it 'dip' but not completely go out.

Contrast this with, say, a fluorescent lamp which completely extinguishes 120 times a second.

 

[GoldDigger]

The current drops to zero but the light intensity will not. The filament can't cool down fast enough before it gets re-heated on the next half cycle. As Gar said, it you looked at it with a fast enough camera, would see it 'dip' but not completely go out.
istence
Contrast this with, say, a fluorescent lamp which completely extinguishes 120 times a second.

Actually how low the light goes from a fluorescent depends on the persistence of the phosphors. The same for "white: LEDs,
I have some LED bulbs that glow visibly for as much as 5 seconds after they are turned off, and I do not think DC filtering is responsible.
The traditional cheap strobe (like for adjustible speed phonographs) is a neon bulb where the light output does go to zero for a substantial part of each half cycle.

 

[Besoeker3]

Contrast this with, say, a fluorescent lamp which completely extinguishes 120 times a second.

Don't think so.
"However, since ultraviolet rays are not visible to the human eyes, the inside of the glass tube is coated with a fluorescent material that converts ultraviolet rays to visible light. It is this coating that causes fluorescent lamps to glow white."

 

[AdrianWint]

Don't think so.
"However, since ultraviolet rays are not visible to the human eyes, the inside of the glass tube is coated with a fluorescent material that converts ultraviolet rays to visible light. It is this coating that causes fluorescent lamps to glow white."

I don't dispute the mechanism that is used to create the light. The fluorescent lamp is a discharge lamp, it is the arc that creates the UV.

So, if a fluorescent lamp isn't 'flashing' at twice the mains frequency then how & why does it create the stroboscopic effect with moving machinery?

 

[Besoeker3]

I don't dispute the mechanism that is used to create the light. The fluorescent lamp is a discharge lamp, it is the arc that creates the UV.

So, if a fluorescent lamp isn't 'flashing' at twice the mains frequency then how & why does it create the stroboscopic effect with moving machinery?

Good point.

 

[Besoeker3]

Good point.

But found this:
"If the ballasts are electronic, then no problem as the flicker frequency is too high to be a problem.

If the ballasts are copper/iron, but spread over 3 phases in such a way that the moving are parts are lit by lamps on at least two phases, then no problem.

If the ballasts are lead/lag pairs in twin fittings or adjacent fittings, then no problem."

 

[Ravenvalor]

Perhaps what we are seeing with fluorescent is harmonics?

 

[GoldDigger]

I don't dispute the mechanism that is used to create the light. The fluorescent lamp is a discharge lamp, it is the arc that creates the UV.

So, if a fluorescent lamp isn't 'flashing' at twice the mains frequency then how & why does it create the stroboscopic effect with moving machinery?

Fairly simple, as applies to a single tube lumenaire or a two tube luminaire fed from single phase and without phase shifting in the ballast:
The UV arc has a fairly pronounced flashing effect, with the arc extinguishing completely for a large portion around each zero crossing based on the lowest sustained discharge voltage. The phosphors, particularly those with a short relaxation time, will smooth this out considerably but will not completely remove the strobe effect. It is a continuum:
A xenon flash lamp with a very fast capacitor discharge arc will provide the most pronouced strobe effect.
A neon bulb provides a distinct pattern with a high contrast ratio between peak and average.
A single phase line frequency fluorescent will have a less pronounced strobe effect, but still detectable, particularly with a moving machine part as the target.
Even an incandescent bulb will still have some strobe effect as the filament temperature changes. You just have to have a clear high contrast target and look carefully to see the effect.

 

[winnie]

With an AC powered light source you will have some flicker.

Incandescent sources have their thermal mass to reduce this flicker.

Florescent sources (including phosphor based LED sources) have the persistence of the phosphor.

The life reduction that gar described for DC operation of halogen lamps is generally not an issue for low voltage or high wattage lamps, but can be large for low wattage high voltage lamps. You don't want to run a 50W halogen at 240V DC. But a 20W 12V lamp should be just fine.

Back to the OP: you might try companies selling yo the boating market, or you might buy lightning made for 12V AC and substitute a DC power supply.

Jon
Jon

 

[Flicker Index]

211106-2047 EDT

Ravenvalor:

If you consider an ordinary tungsten filament bulb, and excite with the same power input ( meaning same filament temperature and light output ),
then compare lamp life between DC power and AC 60 Hz you will likely find life at DC to be possible 1/10 that at 60 Hz.

Now change to a halogen bulb that will run at a higher filament temperature, has a brighter output, when operating at its nominal voltage, and compare its life with an ordinary filament and ordinary gas ( likely nitrogen ) in the bulb, and you may find a longer life even though brighter. Reduce the input voltage so the bulb runs cooler, and you will loose that increased life. The reason is that the internal temperature is not high enough to cause redistribution of tungsten back on the filament. I can not tell you how much difference there is in life of a halogen bulb between AC and DC when operated at is nominal voltage.

If you take an incandescent and operate at 60 Hz, and look at its output with a fast enough photo detector, then you will see a small 120 Hz modulation of the light intensity. Not a hard experiment to run.

.

Actually 40W incandescent lamps contain enough flicker to cause banding on camera phones depending on electronic shutter speed used by the exposure control. T8 lamps ballasted with high quality electronic ballasts (whose costs were in excess of $20) have less flicker than just anything else out there other than special theatrical lamps or battery operated lights that do not use PWM.

These days, a lot of LED lamps employ LED ballasts with topology designed to be cheap and small enough that let through a lot of flicker and contain as much, or more flicker than metal halide lamps. Lumen-for-lumen, LED elements have always been more expensive than gas fluorescent (mass made spirals and GSFL linear) that designers have taken a lot of compromise on the LED ballast to remain cost competitive. So, actually LED contains a lot of flicker that marketeers like pre-Ideal Industries Cree's commercial lighting division criticized "fluorescent lights" about.

Also, if you take high speed photos of LEDs and fluorescent lamps that contain flicker, there's not only output level modulation, but color modulation as well. When the arc shuts off in a fluorescent lamp, there's some persistence. This color persistence has different spectrum output than when arc is powered. When you're viewing videos on YouTube, I think we've all seen people's faces that slowly fade back and forth between green and pink tint. This is caused by color flicker as well as flicker content causing auto white balance to get confused.

 

[Ravenvalor]

Thank you for taking the time to share with me this interesting info.
Do you think that a company like Phillips is producing high quality, flicker free, correct color (as advertised), LED lamps for the mass market?
I heard that the latest Amazon Kindle Oasis 2019 edition has gotten the flicker under control.
As far as the 12v DC halogen is concerned I will look into it and let you know what I find.
120v AC halogen is still a big hit with customers who want a high quality light in their chandeliers, pendant lights, and some table lamps.
We use about 90% regular incandescent and halogen in our home.

Thanks again.