reducing power to holiday lights

davejames

Hi All, and a very early Merry Christmas!

It's that time of year when I decorate the house and a couple of trees with lights.

Thinking about the increase in my electric bill, I wondered if there was a way to reduce the power to the lights (to save money) and not reduce the brightness too much.

I think there's an easy was to do this (conceptually), but I want to bounce the idea off of you experts in case I'm missing something.

The idea is to run the lights off of 1/2 wave rectified DC by inserting a diode in the hot side of the AC line. The "diode" will probably be multiple diodes in parallel to handle the power. I'll need to do some measurements of the light strings to size the diode array correctly.

Oh yeah - the lights themselves are incandescent, not LED.

I'm thinking the persistence of vision thing will fool my eyes into seeing the lights more on than off.

I'm also thinking that with the lights being incandescent, there won't be a lot of electrical noise being generated due to the inductance of the filaments and inherently slow turn on/turn off action.


Thoughts?

brucee

While diodes would reduce the power for incandescent, putting a number in parallel is not a good idea.

Diodes and transistors have temperature coefficients that when they heat up, the internal resistance decreases. So that they can exhibit thermal run-away, where one device starts conducting more current than the others, which heats up, conducts more, so eventually it tries to take all the current and eventually fails.

I don't know how electric meters work enough to know if they would average the power of a light with a diode, and reduce your bill.

In the long run it would be probably cheaper to just switch to LED strings. I have over 500' of LED lights running and it consumes less than 60 W (measured with a KillAwatt meter). Add that with a timer so they only run from dusk til 11 PM.

Hal Albach

Perhaps an off the shelf light dimmer? Available in ranges from 150 to 1000 watts, most common is 600 Watt. You can then use it for other lighting after Christmas.

erco

One big diode should work fine and it's easy enough to try. Remember the "energy saver buttons" that would stick on the bottom of an ordinary screw in light bulb? Just a diode. Supposedly tripled bulb life, saved half the energy and still gave off 60% of the light. Probably shifted the color spectrum a bit too, I'll wager.

Hal's triac dimmer suggestion is next simplest, if the diode route isn't bright enough.

Edit: Extends bulb life FIFTY times! http://www.ebay.com/itm/New-Lemra-The-Button-50x-Longer-Light-Bulb-Saver-UL-Listed-3-Pack-/200995123138?pt=US_Lighting_Parts_and_Accessories&hash=item2ecc3e2fc2#ht_4302wt_918

erco

davejames wrote: »

I'm thinking the persistence of vision thing will fool my eyes into seeing the lights more on than off.

Glass half empty or half full?

Lights half on or half off?

tonyp12

Of course there is not magic trick to half the electricity and still keep 80-90% of the light
Not talking about going from incandescent to led etc.

What happens if you put two incandescent strings in series at the outlet itself, will 57volt be 60% of the light?
Easy to make a 1-in-2-out-adapter that have been wired up in series and will help with outlet shortage.

skylight

make each string flash on and off, with enough time in between allowing for all the lights you have you could get away with just one string on at any time.....just think of the savings!

Mark_T

If you run high power incandescents at lower average current the filament runs cooler, which
extends life and makes them a little more orange in hue.

If you power low power incandescents this way the filament may have such low thermal mass
that it heats up and cools down enough per cycle to stay properly white half the time, but perhaps
you actually reduce filament life through thermal cycling. I remember from my childhood how
often xmas tree lights failed and that you had multiple spares of different colours in the box!

Changing to LED lights will drop the power consumption dramatically and you get a proper
range of colours (incandescent blue is never very convincing!). Especially as LED light strings
seem to always come with an effects box to pulse and strobe them (again reducing average power
consumption)

A fun way to reduce power consumption for external lights might be to use a movement detector
to control the brightness - someone comes by and you fade them automatically up! Probably more
impressive than just being bright and numerous.

NWCCTV

Paint all the light bulbs using flourescent paint. Turn on one black light and voila!!!! Instant savings!

davejames

All - thank you for the inputs.

I see and understand the uneasiness of some concerning paralleled diodes.

So it looks like the dimmer approach would make the most cents (ha ha - get it? "cents"? ...uh-huh...whatever, Dave).

Erco - the "button"...yup - that's where I got the idea originally.
NWCCTV - you're silly

JonnyMac

You might consider a small VariAC. That will let you dial in the brightness that works.

http://www.allelectronics.com/make-a-store/item/SC-5M/5-AMP-VARIABLE-TRANSFORMER/1.html

davejames

JonnyMac wrote: »

You might consider a small VariAC. That will let you dial in the brightness that works.

http://www.allelectronics.com/make-a-store/item/SC-5M/5-AMP-VARIABLE-TRANSFORMER/1.html

Mr. McPhalen - thank you for the response.

Pray tell, do you have a preference for a variac over a triac-dimmer?