Continued from 2016-09-03 post.
Back to the light bulb. To clarify, we are only discussing the original incandescent light bulbs, not the newer ones. This also applies to the 115 volt AC light bulbs. Other voltage lights would have to use different values.
Warning! Also you indemnify (hold me harmless), me, the author, against any claims for any harm. I can’t prevent you from doing something stupid like electrocuting yourself.
I want to tell you a secret. There must be a conspiracy among light bulb makers to have kept this secret for so long, that almost no one knows about it. And the light bulb makers have prevented the US consumers from taking advantage of it by conspiring to prevent consumers from obtaining them. Why? Because if they could, any consumer in the U.S. could buy a light bulb made for 230 Volts AC and put it into a light socket that has 115 volts AC, and it would last for many, many thousands of hours! Maybe it would work for decades! There must be a conspiracy! :-O
I have never seen a 230 volt light bulb sold in any store here in the U.S. Of course, the light from this bulb might not be acceptable to consumers because it would be dimmer than a regular 115 volt light bulb. But there is another way to get longer life out of a light bulb. All you have to do is lower the voltage. There are several ways to do this, but I’ll discuss one simple way. You can put a resistor in series with the light bulb. I calculated that by adding a 15 ohm, 10 watt resistor in series with a 75 watt light bulb, it would lower the voltage by about 10 volts. The light should have about 105 volts AC across it. You could increase the resistance a few ohms to reduce the voltage a bit more. This should extend the life of the light bulb to about double its rating. This also has another small advantage. The added resistor reduces the surge current when the light is first turned on, so there is not as much stress on the filament. This may help extend the life somewhat.
You could get 10 watt power resistors online, but they aren’t easy to find in stores, so another way could be to use another light bulb in place of the resistor. It would have to light up at 12 volts, and draw about 2/3 of an amp. A car light can be used. The lower power (tail light) filament of the 1157 stop and tail light uses 14 volts at about 8.3 watts, which calculates to about 0.6 amps. But because tungsten changes resistance depending on the temperature, it is hard to say what the current will be when it’s in series with a 115 volt light. Also the 12 volt car bulbs have a thicker filament which takes longer to heat up, so the full 115 volts may be across the 115 volt light when it’s first turned on, and that is the time when a filament has the most stress and usually burns out. So this may not be as effective as a resistor. Also, the 1157 filament will eventually burn out, but it’s hard to predict how many hours it will last.
However, you could also get extended life from your lights by using a transformer. Let’s say I have a transformer that has a primary that takes in 115 VAC and a secondary that puts out 12 VAC at 1 amp. I connect the primary to 115 VAC, and the I connect the secondary in series with the ‘hot’ or line side of the 115 VAC. There are two ways to connect the secondary, series aiding, so the voltage is 115 plus 12 volts AC or 127 volts AC, and series opposing so the voltage is 115 minus 12 volts AC or 103 volts AC. Bingo. You can connect the light to 103 volts AC and the light will last many times longer than at full voltage. However it would cost much more than the resistor and more than the cost of many light bulbs, so it would probably not be cost effective. It does have one good use. If you have Japanese appliances that use 100 volts AC, this is a good way to make them run properly on 115 VAC.
I might add that this does not work with the newer CFL and LED lights because they have a power supply that may work all the way down to 85 volts AC, so the light will just take more current at a lower voltage and stay the same brightness. Or if they are really cheaply made, the light may not work at all.
I continue this on my next blog.
Are you aware of any countries that run MORE than 115 VAC?
What i meant to say is: Any country running a little more than 115 VAC, but less than 230 VAC ?
TY Tom H
Well, that depends on whether or not you consider it purposely or not. In India, some power grids are so severely overloaded that the ‘mains’ voltage is down to 190 volts AC. That’s not temporarily, that’s chronically, due to power thieves. Local ‘pirates’ have a tall ladder, and for a price, will climb up and connect your home up to the grid. Of course it’s hot and humid, so everyone has air conditioning, and that just overloads the electrical system, no matter what time of day. The power company comes around and disconnects them but the pirate just hooks them up again.
I was watching a program about this on TV. They showed a guy standing on top of a huge oil filled transformer, which was smoking and the leaking oil was burning. He was pouring water on it! That’s NUTS!
Another simple way to dim an incandescent light bulb is to half wave rectify the AC power to it using a cheap diode, (1N4003). Works great and is more economical as it doesn’t dissipate power like a dropping resistor or transformer does. Sorry for the late post!
Thanks for the comment. One source of information that I read described a problem with DC and incandescent filaments. The DC is positive on one filament end and negative on the other. There can be a greater loss of tungsten from one end, compared to the other, over its lifespan. The filament on one end then gets thinner and fails earlier. I don’t know how important that is because auto lights don’t seem to have a problem. But then they have only 12 volts, not 120 volts, and their filament is much thicker.
For years I used a soldering iron with a switch and a diode for half power. Worked just fine, and made the tip last longer.
Now incandescent lights are a dying species. Soon most all lights will be LEDs. But fridges, dryers and ovens will have to wait. I think someday they will use optical fibers to get light to very hot and cold places. Or maybe mirrors.
I don’t believe the diode will work with the converters in LED or CFL light bulbs. The converter will just suck twice as much current during the conducting half cycle.
Someday perhaps they will figure out how to gather sunlight during the day and then release it at night. 😉