Resistor for cutting 12v in half

[Shasta1]

Is there a resistor that can be used to cut 12v in half?

I'm wanting to dim a couple of bulbs to half brightness.... is there a simple and inexpensive solution to this? The bulb is the 1141 size base.

[scubieman]

Do a search for a 12v dimmable switch in google . Lots of options.

[Shasta1]

Yes, did that before I posted the original question.
I don't find $30+ inexpensive for the ability to dim a bulb.

[BigDTx]

i would check Radio Shack they should be able to guide you in the right direction. Can't you just put a variable resistor in line like a dimmer knob in your house? they are cheap!

[scubieman]

Not sexy but works.

LED Light Dimming Switch Box 12V | Virtual Village - US

[BigDTx]

Originally Posted by scubieman

Not sexy but works.

LED Light Dimming Switch Box 12V | Virtual Village - US

that is what I was talking about, something along those lines.

[Shasta1]

My previous searches turned up that box on ebay for around $3-4. Certainly an option, but a little bulky and exposed wires.

I'm looking to dim a living room light that we like to have on when watching tv. It's just too bright and distracting. I didn't know if lower wattage bulbs were available, or if adding a resistor (value??) would work. I'm looking for about half the light output.

[kz08h5]

A 1141 bulb appears to be a 18.5 watt bulb. You could put a resistor in series to cut the light out put but it would have to be at least a 10 ohm 10 watt resistor and you will need one for each bulb you want to dim. And you won't be able to dim them. If you want the light output decreased without the ability to dim I would call a place like Easternlightbulbs.com (I have nothing to do with them). They should be able to tell you what bulb you could use to replace your current ones.

[Shasta1]

Thanks kz08h5!

That's what I was looking for.

Actually, what I found out today is that a 5 ohm to 6 ohm, 10watt should approximately reduce the brightness by 1/2.

I'm going to assemble a small rotary switch and use three taps; full, 1/2, and 3/4 brightness. I think I found one that will mount right in the fixture.

I'm planning on using this on two light fixtures; one in the tv area, and one over the headboard of the bed. My fixtures are the typical 2 bulb/two position switch, so the second position on the fixture will always be full glitter.

I've happily replaced the first position bulbs with the 32 led boards in all the other fixtures in my rig, and very pleased with the results! I found that info in this thread: http://www.forestriverforums.com/for...ults-9233.html

Thanks for the link to Eastern light bulbs. Eventually I'm going to get up to speed on LED's and make my 1/2 & 3/4 brightness bulbs using them.

Thanks again to all for your replies. This is a great forum.

[LadyWindrider]

You can't reduce the brightness on LED bulbs by using a resistor. Also, those 10 watt resistors you have found will put out a lot of heat, so make sure you allow for that if you put them in the existing fixtures. Also at 5 ohms, you will only be putting about 4 volts to the bulb, probably won't even come on. I would look at a 2 ohm resistor, or make a reflector, or switch it for an led bulb with less lumen s.

[Shasta1]

This post is in reference to an 1141 bulb.

At 5 ohms I'm measuring 6.8volts.....approximately 1/2 the voltage, and approximately 1/2 the brightness. I'll use a 7 or 8 ohm resistor for the 3/4 brightness position.

Heat is a concern. After several minutes under power, I have no difficulty holding the resistor in my hand, the bulb is noticeably hotter.

I'll double check the entire assembly at length for heat before I enclose it in the fixture.

Didn't mean to give the impression that this will work with an LED. Eventually I'll find a small array of LED's that will give me the half brightness I'm looking for. When I learn more about LED's, I'll probably build my own boards, which will also greatly reduce the energy draw, as opposed to the incandescent bulb/resistor.

[edman87k5]

What about painting the inside of the lens white? I am thinking of doing this to the light over the head of my bed.

[F and E Damp]

The "dimmer knob in your house" is actually a thyristor which only works on AC. It wouldn't work on 12VDC.

[DAISY BOYKIN]

Windrider is 100% correct about the resistor getting hot. Better make sure the resistor is not touching anything that is combustible . Why not just use a lower wattage bulb?

[Shasta1]

Well, the answer to my situation was found at Walmart....

"ritelite" wireless led puck. 2 brightness settings, auto-on for use in cabinets or closets, and selectable direction of light.

Who'd thunk????

$6.97

Don't particularly care for battery operated (3 AAA), but this just might do what I need in both tv and bedroom locations.

[ohcnda]

Originally Posted by Shasta1

Is there a resistor that can be used to cut 12v in half?

I'm wanting to dim a couple of bulbs to half brightness.... is there a simple and inexpensive solution to this? The bulb is the 1141 size base.

use a lo93 bulb instead, it is 9.3 watts, much dimmer

[Shasta1]

Thanks ohcnda!

Excellent suggestion. Where do I find these?

I did a search and it seems that this bulb is used in landscaping lighting and pools. I'll check the Home Depot, Lowes, and Ace type stores.

Thanks!

[kalik282]

Here's a chart showing most DC incandescent bulbs and their voltage/wattage (CP)...

Bright Future International Ltd-Auto bulbs, Halogen bulbs, Incandescent bulbs, Miniature bulbs, Indicator bulbs, Night bulbs, Neon bulbs, Telephone bulbs LED bulbs.

Enjoy.

John

[Shasta1]

That lo 93 bulb is rather elusive.....haven't found one yet.

[fbroussard]

I found some lower wattage bulbs at automotive store, drastically reduced the amount of heat and still has plenty of light, original bulbs deformed the lens when child placed blanket over fixture in bunk. very happy with the lower wattage bulbs.