I have about two dozen 12 volt Incandescent lights (ho scale) and a 300 volt (0 to 130 volt) 3 amp variac transformer. Most of these lights are in flood light towers and railroad signels. I would like to run them at 8 volts max so they will last longer. So can I use the variac for this?
Best to start with a 12 volt transformer. Then use the Variac on the primary of the transformer to reduce the transformer output to 8 volts. This would put the Variac output at abpout 80 volts; a very comfortable value. Setting the Variac output directly at 8 volts is not practical.
BTW, incandecent lamp life varies approximately as the fourth power of applied voltage. A little reduction goes a long way to extend life.
Charlie - Northern Colorado
presumably you have a 12V power supply and want to use the Variac to reduce the 110VAC to the 12V supply to reduce it’s output. is this what you’re suggesting?
or could you possibly be suggesting to drive the lamps from the Variac, reducing the 110VAC to 8VAC??
there are inexpensive adjustable step down converters from ebay that can be used with a 12V wall wart or any other DC wall wart > 8V lying around that can safely be used to adjust the lamp voltage
And then I run the 80 volts to the lights???
“And then I run the 80 volts to the lights???”
NO!
The Variac output must be connected to the primary of a 120V to 12V stepdown transformer! Then the transformer secondary is connected to the lamps. Greg’s approach will also work but it must be used with DC supplies only. The Variac will only work with a true transformer, preferably a 12V transformer. The Variac cannot be used with DC supplies.
Charlie - Northern Colorado
Yikes!
That guy better hire an electrician before he kills himself.
Rich
I would never do this. 8 volt power supplies that are modern and safe are not expensive.
Yes, I am the guy that prefers 40 year old Troller power packs.
-Kevin
I agree with Kevin. KISS Keep It Simple, See?
You can get an 8 volt supply for a few dollars off eBay. Add a fuse holder and a small fuse for a dollar or so, and you have a simple, robust and pretty much failproof system. I run all my incandescents off 12 volt supplies. The 16 volt bulbs I use glow happily and will last forever with the lower voltage.
So this 8 volt supply will have enought juice to push my 2 dozen lights? Look I am asking these questions first so I don’t kill myself. It’s those who don’t ask that are looking up at dirt. Cut me some slack.
don’t know how much current the lamps require without knowing the type. this T-3 type draws 0.33 A at 13V
don’t know what power supply you have and how much current it can supply
these step down converters can handle 3A
2 dozen lamps drawing 0.33 A requires ~8A