AC or DC power for lighting, any difference?

Works for me. You can even use the same ground. 

I decided to use DC.  You can find inexpensive, UL certified, fixed voltage (12 VDC) power supplies that will do the trick.  If you use LEDs, 1 supply can go a long way.

George

Lionel Trains run on AC. They only offer AC transformers. Everything about Lionel is AC so why would they recommend powering anything with DC. 

I've read arguments that DC power gives longer bulb life and arguments that AC power gives longer bulb life. (Uberstationmeister mentions filament notching above). I use AC because I have the  variable voltage power supplies on hand.

Bulb life is greatly extended by running the bulbs at voltages that are slightly lower than rated. GE published lots of information on this in their miniature lamp catalogs.

I too have heard that powering lamps with DC will extend their life.  Any electrical engineers out there who can put this to rest ?

In practical reality there is no difference when you are talking an incandescent bulb, they work equally as well with DC or AC, to get the same amount of light out of the bulb you use the same voltage/power. People have theorized that DC will extend the life of the bulb because A/C is constantly changing its direction and that "wears out" the filament (I suspect some of this went back to the DC vs AC wars where Edison was finding any claims he could to denigrate AC), others say AC makes it last because of that and both of them are based in gut feeling rather than science.  I agree with others, Lionel said use AC because that is how they powered their trains, it isn't because the bulb will last longer. Bulb life is determined by how hot it runs in producing the given light and the quality of the filament, one way to extend bulb life is to run it below its rated voltage since it will run cooler (though give less light, obviously). 

At higher voltages, 120 volts, there an arcing problem when the filament breaks when using DC. Many higher voltage DC  bulbs are evacuated to help with arc suppression.  But this results in the lamp darkening in time due to tungsten being deposited on the inside of the glass. The largest use of low voltage lamps must be the automotive industry, which are all DC. Many of the common lamps used by Lionel are number 53 and 363, which are both automatic entry lamps.  In toy train usage, either AC or DC on lamps should work equally well.  Keeping the voltage as low as possible will give the best results. 

Bulbs do last longer on AC. The reason bulbs last slightly longer when powered from AC is on DC more electrons are boiled off the negative end of the filament than the positive end so it wears unevenly and fails a bit sooner.  On AC the wear is shared more even on both sides of the filament.  The difference is fairly small, but it's a measurable effect.

gunrunnerjohn posted:

Bulbs do last longer on AC. The reason bulbs last slightly longer when powered from AC is on DC more electrons are boiled off the negative end of the filament than the positive end so it wears unevenly and fails a bit sooner.  On AC the wear is shared more even on both sides of the filament.  The difference is fairly small, but it's a measurable effect.

You know, that's interesting.  I always thought bulbs running on DC lasted longer.  You learn something new every day...

I run all my 14v lighted accessories off an Astron SL-11A DC power supply.  It has great capacity and I got it real cheap 20 years ago.  I haven't notice any real difference in bulb longevity.  

Tony

We're talking a couple of percentage points I believe, so in real life, it would be hard to tell the difference.

Using AC to run the trains but took out all the old Iron core transformer that used to run my layout lights and put in 3 old computer transformers that run on pure DC with no fluctuation in voltage  They cost me $10. each and have been on the layout for many years.  They also produce 3, 5 and 12 volts and of course that can be varied by putting resistors in line if necessary with the layout lights.  This is one of the best things I did with the layout lights because I found that by using the older Lionel AC iron core transformers the voltage varied just enough to give a small flickering of the lights.  I use both led's and incandescent bulbs for building lights.  I do prefer the incandescent bulbs because they are not a pure white light and resemble the old Edison bulbs.  I don't think I have ever replace a light bulb on the layout in 20+ years and I do run them at a lower voltage than specified.  I guess this is all a matter of what the operator prefers for his layout.

Bulbs do last longer on AC. The reason bulbs last slightly longer when powered from AC is on DC more electrons are boiled off the negative end of the filament than the positive end so it wears unevenly and fails a bit sooner.  On AC the wear is shared more even on both sides of the filament.  The difference is fairly small, but it's a measurable effect.

John's comment matches the last information I found on the web.
I was looking into the pros and cons of AC versus DC when I was lighting original prewar and postwar lamp post bulbs. At the time, I don't think there were any reproductions available for the #64 lamp post bulb and the reproductions for the other lamp posts really didn't have the correct finish.
There are reproduction 64 lamp post bulbs available today, and I think the finishes are getting better, but they still don't match the original finish.

I don't have any lamp posts wired up right now. When I get some hooked up, it will be on AC, with the voltage set somewhat under the rated voltage. I doubt anybody could tell the difference in brightness.

FWIW, you can have LED's in any color temperature, and I've taken to using some LEDs for steamer headlights that have exactly the color temperature of the incandescent bulbs I replace, around 2700K.  The difference with the LED is no heat and a focused headlight that actually looks like the real thing.  Running in the dark with the headlight shining on the rails really does add to the realism, it's a cool effect.  You don't get that with most incandescent headlights as they emit much less light in general and even less out the headlight lens.

gunrunnerjohn posted:

FWIW, you can have LED's in any color temperature, and I've taken to using some LEDs for steamer headlights that have exactly the color temperature of the incandescent bulbs I replace, around 2700K.  The difference with the LED is no heat and a focused headlight that actually looks like the real thing.  Running in the dark with the headlight shining on the rails really does add to the realism, it's a cool effect.  You don't get that with most incandescent headlights as they emit much less light in general and even less out the headlight lens.

Interesting information!

I have an old (circa 1983) Lionel transformer that uses DC for the train (variable) and AC for accessories (fixed at 19 volts). I guess this is opposite of what Lionel typically made? It came in a cheap set made in Mexico, military set with plastic trucks and wheels. It barely lights my street lights (have 12 of them wired in parallel). I like being able to control the dimming with the DC side, but I'll try to find a 2nd hand AC transformer that puts out more power.

That's the HO standard for transformers as a rule.

I guess this is opposite of what Lionel typically made?

Postwar Lionel HO 0100 and 0104 transformers put out DC for the trains and AC for the accessories.
I believe the 0102 transformer did as well.