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Old 02-21-2008, 05:15 PM   #1
twelvenine
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Default dc current in 60W light bulb?

kind of a dumb question, but would it be possible to power a regular light bulb(like 60W from a light fixture) using dc current(batteries)? i always figured that it wouldn't really matter as long as there was some kind of current dissipating in the filament. the bulb didn't say AC specifically. i tried this out yesterday when my power went out: two 9V batteries in series connected to a 60W bulb. i figured it would at least look kinda dim, but nothing happened. i'm pretty sure the wires were connected right, so either there wasn't enough power, or dc doesn't work?
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Old 02-22-2008, 07:25 AM   #2
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To be honest, I'm not sure. I know light bulbs can be DC, but is there a difference between those and normal household bulbs?

I was fiddling with some wires recently, trying to get little fans to work using batteries and testing out small transformers, but I was having a few issues. It seems to me that things can work with less current, but not a whole lot less.

What I would try is getting a nice, dim bulb, say 20 watts. If that doesn't light up with two 9v batteries, your question may be answered.

- - - - -

Here is another thing to think about: you're trying to match 9 volt batteries with a 60 watt bulb, when watts and volts aren't the same thing. We need to define the terms.

This is a very basic analogy with a lot of holes, but compare electricity to moving water. Your backyard hose has fairly low pressure or force. If you put your thumb over the end of it, the same amount of water comes out with a lot more force. This is voltage, the force of the electricity? Now think of the Nile or the Amazon, incredibly huge rivers. For the most part, they move rather sluggish, but the volume of water is just massive. This is like amperage, the sheer number of electrons moving through the circuit. I'm probably butchering this, but one volt and one amp of current in a circuit means that the circuit is one watt.

I hope this helps.
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Old 03-06-2008, 06:21 AM   #3
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As long as your light bulb is a filament kind, no problem!

You will need a bit more 'power' though, as in more Volts.

Although I at the moment cannot remember the formula out of my head, you can calculate the continous voltage over the bulb when the normal AC outlet is used. Lets say that with 120 Volt 60 Hz the continuous voltage is something like 120 Volt to make the calculation easier (the AC is of course a sine wave, and not DC), so in that case your current will be:
Power (Watts) = Voltage (volts) * Current (amps)
P = V * I >> I = P / V = 60W / 120V = 0.5 Amps

In your batteries case the current would be:
I = 60W / 18V = 3.33 Amps, a bit too much out of ordinary batteries! Plus of course in order to make your bulb glow a while you need a bit more power in your batteries: for 1 hour you need 60 Watt/hour, the average 9V battery has a capacity of about 0.15 Amp/hour. You also need of course enough Volts to make the filament glow anyway.

But, a few more batteries of a larger size will do the trick.

By the way, having said that you will need a bulb with a filament, I did run into an energy savings bulb the other day that runs on 12V DC (for campers etc.)! This was at the site of Conrad (Dutch), but surfing will probably bring you the same. Of course a filament bulb is not very energy saving, since very much of the energy is wasted into heat.

Last edited by luigi01; 03-06-2008 at 06:26 AM.
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Old 03-06-2008, 11:34 AM   #4
Gabriel Torres
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Hi there,

Light bulbs can be connected to either AC or DC sources. They work just fine. The problem is if you use a 60 W x 120 V light bulb connected to a 9 V battery it won't produce enough light. If you want to play with this, consider buying a light bulb compatible with the DC voltage you are willing to use (6 V, 9 V, 12 V, for example).

Cheers,
Gabriel.
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Old 06-23-2008, 05:13 PM   #5
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edison base bulbs are meant to run on line voltage (120 in north america and around 220-240 i think is european standard)

try using a low voltage bulb (12v) or an LED (with a resistor) or take a bulb out of a battery powered flash light.


Oh and don't bother testing batteries on compact fluorescents bulbs, those low wattage bulbs contain mercury and if you don't provide enough power the ballists fail and melt themselves. People have actually burned their house down using compact fluorescents. Plus the energy savings is very very negligible.

oh the fun of working in a lighting store
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Old 07-05-2008, 08:34 AM   #6
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Default dc -- light bulbs

yes. but it takes a lot of batteries to get to 120 volts. don't expect much light from 2 nine volt batteries in series.
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Old 11-22-2008, 06:23 PM   #7
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Default it works!

so i rigged up 12 9v batteries together.... they were only putting out about 108v according to my multimeter... however i was able to light up the bulb!

the DC works even though they tipically use AC

use a 60 watt bulb!
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Old 01-23-2010, 01:17 PM   #8
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Default Interesting

I got some 'things' from someone in 1986. They are round like a button and have a sticky sponge material which allows you to stick one on a incandescent light bulb.

These buttons convert A/C to D/C so your bulb runs on DC current. The only drawback is that the bulb is less bright than it would normally be.

I have a light fixture that is above my sink in my bedroom with 5 designer bulbs in them. I stuck these buttons on all 5 in 1986ish. four of them are still burning just fine in 1010. One bulb did burn out last year.

I just put that button on a bulb in my kitchen which burns out very often.

Wish I could find some more of these things.

Anyone else ever hear of them?
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Old 01-24-2010, 10:31 PM   #9
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Quote:
Originally Posted by Mpilchuk View Post
These buttons convert A/C to D/C so your bulb runs on DC current.
So it's a simple diode then, acting like a half wave rectifier?

While it might be good for the bulbs I don't think it's good for your local power grid. If my assumption is correct each of these devices will cause fluctuations in the power draw during each 60Hz cycle, resulting in anything but a nice sine wave curve. (Can be controlled using a basic oscilloscope.)

When bulbs blow too often it's usually because the cooling is insufficient with that mount. The obvious solution is to use lower wattage light sources.
As an example I have a ceiling lamp rated for max 2x 60W bulbs. I immediately realised that the cooling was very low, so I tried 40W bulbs. Those died in three months or so. Replacing them with 25W bulbs was good enough to keep them alive for about a year, which is still way below rating. Now I use 7W energy savers, and these really do survive!

Cheers
Olle
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Old 01-31-2010, 02:32 AM   #10
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Quote:
Originally Posted by Mpilchuk View Post
I got some 'things' from someone in 1986. They are round like a button and have a sticky sponge material which allows you to stick one on a incandescent light bulb.

These buttons convert A/C to D/C so your bulb runs on DC current. The only drawback is that the bulb is less bright than it would normally be.

I have a light fixture that is above my sink in my bedroom with 5 designer bulbs in them. I stuck these buttons on all 5 in 1986ish. four of them are still burning just fine in 1010. One bulb did burn out last year.

I just put that button on a bulb in my kitchen which burns out very often.

Wish I could find some more of these things.

Anyone else ever hear of them?
any chance you could provide an image of these "buttons"?

I am somewhat confused, you have a sink in your bedroom or a bathroom?

If a bulb is readily burning out in the same location, you may have a problem with that specific fixture. Not all bulbs are made to the same quality control and some better quality bulbs will have a larger percentage of tungsten than other, ensuring a longer life. As Olle has already eluded, the temperature is also a big factor, but with lower wattage comes lower luminosity.
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