Powering my 40 watt light bulb

[rbewley]

Hi,

 

I'm trying to power my 40 watt lightbulb, and I've been at this for a bit, and was told this morning I would need 22,000 "C" batteries, which seems like it would make my lightbulb explode...

 

Anyway, my standard C battery I am using has 1.5 volts and 7.5 amps when I tested it. Now, my first possible pitful of not being sure is, if I stack these batteries together, I know the volts will just add, but will the amperage stay constant?

 

Now, assuming the amps did stay relatively constant, I figure it would take 5.3 volts to power my 40 watt lightbulb. This is using the following equation:

 

P = iv

40 = 7.5x

x = ~5.3

 

Now, assuming 1.5 volts per battery, i figure that 4 C batteries should more than do the job.

 

So, with my 4 C batteries hooked up, I test again the current and voltage. I am now getting 6.1 volts (About what I expected to see) and also 9.5 amps. This is about 58.0 watts, which I figure should power my 40 watt lightbulb.

 

But, now that I have my lightbulb hooked in, it doesn't even glow. And, when I re-measure everything, I find that I get 104 mA and 5.9 Volts, which of course is only 0.6 Watts, not nearly enough to power my lightbulb.

 

My question is, how can this be? Is it the extra ohms of resistance in my lightbulb? Does my lightbulb really pull only 40 watts of power? If so, how come it takes that much...

 

 

Thank you,

Richard Bewley

[Cap'n Refsmmat]

Hook them in series or parrallel?

[rbewley]

Oh sorry, series.

[TheProphet]

The 40W bolb.. is it a 110-130V or 220-240 V bulb?? Probably somone of these. Hence if it was a 12V ud have some light atleast... and the same at 24V!

 

Let's start with saying this.. as im swedish and we use 230V the bulb's resistance is calculated on 230V so it will be consuming around ~0,17A..(inner resistance ~1k35) So in order for u to get this particulary bulb litt u will need atleast a 1/4 of these 230V to get it running at 10W! To do this u need 57,5V which in turn means that u need 38 of those 1,5V batteries or just 6 of 9V, in series of course! I guees u get me now!

[drz]

Yep, I think your problem is that you are trying to power an AC device with DC power.

 

Likewise, a single 9 volt battery hooked to a proper invertor would easily light your bulb.

[TheProphet]

Yep' date=' I think your problem is that you are trying to power an AC device with DC power.

 

Likewise, a single 9 volt battery hooked to a proper invertor would easily light your bulb.[/quote']

 

Even bether explained (and how the heck didn't i think of that.. well it's 03:20 here in sweden.. bet my brain is in away mode )

[rbewley]

Hi,

 

Thanks for the information, it was very helpful. So, are you saying my lightbulb will only pull 170mA no matter how much is available?

[drz]

I'm saying that if you are using a typical light bulb (such as the kind you screw in) then it will not work with DC power. go to wal mart (or your equivalent) and get a headlight bulb for an car. You should be able to power this with pretty much any size battery, however the closer you get to operation voltage the brighter it will get.

 

Can I inquire as to your purpose for lighting a bulb via battery? Why not get a flashlight?

[rbewley]

I have no actual reason to power the bulb, and I disassembled my flashlight. What makes a bulb "AC", and will any amount of DC power work to power the thing?

 

Thanks,

Richard

[drz]

As I mentioned earlier, a 9v Battery through the proper invertor will power the bulb.

 

I don't think you can power an AC bulb with DC power, simply due to the differences in design. You might try checking http://www.howstuffworks.com to see if they can help shed some light.

[Lance]

24VDC though a 120VAC bulb will still make the filament glow and create lots of heat.

 

12VDC makes the filament glow very faintly. I doubt 12VAC would make much of a difference. At lower voltages it’s just not drawing enough current to really do anything. You need to buy a bulb rated at the voltage you plan on using.

[rbewley]

Well, the whole idea behind a filament is, since it just gets hot from the current going through and creates light and heat, I don't see how AC or DC would make a difference. Let me just try pumping up the DC juice a bit and see if I can get the thing to light...

 

Richard

[YT2095]

about 90 "c" batteries is what you`ll need to make your 120v.

 

divide your 120 into 40 and that`ll give your curent usage in Amps. it`s .33 Amps.

 

the bulb is of a fixed resistance, and so no other combination of 40W will make it work.

 

as for this comment "Yep, I think your problem is that you are trying to power an AC device with DC power." LOL, a bulb is neither an AC or DC device, the power source is irrelevent, a bulb is only a resistor in effect.

[swansont]

Anyway, my standard C battery I am using has 1.5 volts and 7.5 amps when I tested it.

 

How did you do this test?

[5614]

as this seems to have no purpose [the lighting of your bulb] why dont you build a plug, its quite easy, and plug your bulb into the mains, and see what happens, and if you think it will be too powerful, build a step-down transformer, thats also quite easy, asuming that you have a iron square with a hole in the middle thing, thats needed in a transformer, hope you know how a transformer works, if not, ask! i can tell you!, but remember transformers ONLY work with an AC current! not DC

[drz]

LOL, a bulb is neither an AC or DC device, the power source is irrelevent, a bulb is only a resistor in effect.

 

I must admit my ignorance as I have never had the desire(nor need) to power a 40w bulb via battery. I assumed, much like you can't take the power wire of your boom box and wire it to a car battery and expect it to work, something in the design of a house bulb prevented it from working on dc. My bad.

 

But thanks for the info.

[rbewley]

as this seems to have no purpose [the lighting of your bulb'] why dont you build a plug, its quite easy, and plug your bulb into the mains, and see what happens, and if you think it will be too powerful, build a step-down transformer, thats also quite easy, asuming that you have a iron square with a hole in the middle thing, thats needed in a transformer, hope you know how a transformer works, if not, ask! i can tell you!, but remember transformers ONLY work with an AC current! not DC

 

Hi,

 

I do understand the concept behind building a transformer (more coils on one side than the other), but if you could explain to me an easy way to build one, I'd appreciate it.

 

Thanks,

Richard

[Guest Proxy-Cypher]

Hey people,

I know this Rbewley chap, i work with him. May I recommend not helping him or encouraging him - he's a bit.... well, has a bit of 'disregard' for certain, eh, precautions. If you tell him how to actually make these things work, he's going to kill himself. I told him that he only needed 4 batteries and that it wasn't working because of the way he wired it just so he wouldn't hurt himself.

 

Thanks

 

- pC.

[pulkit]

I do understand the concept behind building a transformer (more coils on one side than the other), but if you could explain to me an easy way to build one, I'd appreciate it

In essence you need to couple two coils. You can do so by taking a metallic loop made of some magnetic material, and then wind wires on any two sides of this loop. Take count of number loops you wind to take care of voltage calculations.

Also take out leads from both loops, one goes into your source and the other powers your bulb.

[5614]

well, has a bit of 'disregard' for certain, eh, precautions. If you tell him how to actually make these things work, [b']he's going to kill himself.[/b]

 

but at the same time:

 

I do understand the concept behind building a transformer (more coils on one side than the other), but if you could explain to me an easy way to build one, I'd appreciate it.

 

is this true; is my first question, to build a transformer you must use AC, the most common way of doing this is to do so via the mains. this is highly dangerous and may i remind you, that if you do this wrong, you are going to kill yourself.

 

back to the transformers, basically, it is as you said, more coils on one side, than the other, to build one, you need an iron shape! lol, hard to explain, like a sqaure with a hole in it.

 

if you dont know the sape, draw a sqare, then draw another square inside it, eqidistant from the edges of the original square. now view the image as one shape, the hole in the middle, is a hole, the rest is solid iron, except the bit in the middle.

 

now obviously, from the mains, you are going to want a step-down transformer.

 

[transformers work in ratios]

 

to if you attach your input [the mains] and have say 10 coils around one side, assuming the mains gives you 240V, if you want, say 24V output, only have 1 coil on the other side.

 

a formula is:

 

(voltage @ one of the sides call it X) divided by (voltage @ at the other side, call it Y)

is equal to

(number of turns @ X) divided by (number of turns @ Y)

 

(X is the input voltage)

 

 

V1/V2 = N1/N2

 

V=voltage

N=number of turns

1=primary [input]

2=secondary [output]

 

is another way of expressing this, well, ok its exactly the same thing!

 

that should help for the number of turns you want.

 

ask before you do, you must understand this fully to do it properly, remember, mistakes will kill you, check everything, insulate everything, remember electricity can jump gaps, [sparks].

[pulkit]

if you dont know the sape, draw a sqare, then draw another square inside it, now view the image as one shape, the hole in the middle, is a hole, the rest is solid iron, except the bit in the middle

Any magnetic metallic loop will do, specific shapes do not matter.

You can very well wind coils one over the other.

[Lance]

as this seems to have no purpose [the lighting of your bulb'] why dont you build a plug, its quite easy, and plug your bulb into the mains, and see what happens, and if you think it will be too powerful, build a step-down transformer, thats also quite easy, asuming that you have a iron square with a hole in the middle thing, thats needed in a transformer, hope you know how a transformer works, if not, ask! i can tell you!, but remember transformers ONLY work with an AC current! not DC

 

I don't get it... Why would it be too powerful if it's made for the voltage its being used at?

 

Also instead of winding your own transformer you might be interested in simply buying a Variac. A Variac is basically a variable transformer (it has multiple tap points) this way you can set the voltage (normally 0-140V).

 

Hey people' date='

I know this Rbewley chap, i work with him. May I recommend not helping him or encouraging him - he's a bit.... well, has a bit of 'disregard' for certain, eh, precautions. If you tell him how to actually make these things work, he's going to kill himself. I told him that he only needed 4 batteries and that it wasn't working because of the way he wired it just so he wouldn't hurt himself.

 

Thanks

 

- pC.[/quote']

 

He would be more likely to kill himself if he was not educated. Being given false information is even more dangerous.

[5614]

Any magnetic metallic loop will do, specific shapes do not matter.

 

yes, any shape, made of any magnetic material loop will do,

 

iron is the most common, so i suggested that

 

additionaly, i prefer to use a square shape, as if you use a circular one, occasionally, the wires can come loose and slip around, additionally, they have to be made tight in the first place, to stop them moving and sliding, whereas with a sqaure, even if they fall down, it doesnt matter,

 

[sub-question, could you use an unusual shape, e.g. a triangle]? due to the fact that at least two sides are needed for a transformer, and no two sides, in a triangle, are equidistant from each other...

[pulkit]

Aren't transformers with multiple tap points kinda expensive ?

I would've thought its easier to use a voltage regular instead, such as puttin a variable capacitance in series with a fixed voltage.

[5614]

I don't get it... Why would it be too powerful if it's made for the voltage its being used at?

 

sorry, i dont follow

 

Also instead of winding your own transformer you might be interested in simply buying a Variac. A Variac is basically a variable transformer (it has multiple tap points) this way you can set the voltage (normally 0-140V).

 

yes, that is one way! buying it, but occasioanly, people like to build things for themselves! also, this would be more accurate, with the possibility of reversing it into a step-up transformer, thus increasing the voltage, and consequently the brigthness of the bulb,

 

the Variac is limited, although i do own one.