Powering my 40 watt light bulb

[pulkit]

buy a cheap car batt charger, rip out the back end, rectify it to rippled DC then use a 7809 with 3 silicon diodes in series on the Vref (center pin) to pull the voltage up to 11.1 (.7 of a volt per diode) then feed that in as the Base Bias on a pair 2N3055`s in parralel pin for pin, that`ll then drop the output to 10.4 volts

 

ok so it`s .4 of a volt out, but it`s hardly critical and will cost alot less than using a variable V-Reg and all the needed heat compensators

 

I hail thy wisdom !

But a transformer does indeed sound simpler

[5614]

Q) does the amount of wires make a difference, e.g. is there a difference between using 1 and 5 turns, and 100 and 500 turns?

 

[repetition i know, but i think, to help our man building the light, it needs to be answered, so its repeated!

[pulkit]

does the amount of wires make a difference, e.g. is there a difference between using 1 and 5 turns, and 100 and 500 turns?

 

The transformer formula [MATH]\frac{n_1}{n_2}=\frac{V_1}{V_2}[/MATH] is derived under the limit of [MATH]n_1[/MATH] and [MATH]n_2[/MATH] approaching infinity.

[5614]

so ur saying that between the two, n1 and n2, should add up to a massive number?

 

so the more loops the better?...

[pulkit]

so the more loops the better?...

 

The more the loops, the more accurate the transformer formula will become.

[5614]

The more the loops, the more accurate the transformer formula will become.

 

ok, fine, thanks,

 

thats answered all my questions, and hopefully all of rbewley's as well

 

so tell us if you succeed richard, keep us up-to-date, we like to know, see how accurate our transformer is!

 

remember, be careful, mains is 240V, thats enough to kill you, and we dont want that!

 

do ask, if you're not sure, better safe than sorry! even if to be safe, you have to ask basic questions! coz personally, i dont really want you dead, coz i told you to build a transformer from the mains!

[drz]

You know, and maybe this isn't feasible, but why not just use a power transformer for a home telephone? Save you alot of trouble, and probably a store like radio shack has a converter for almost any voltage you need.

 

http://www.alltronics.com/wall_transformers.htm

 

get one of these, wack the end off, one wire is positive, the other negative, at whatever dc volts you order.

 

Chances are you've got a bundle of them tangled up in a box somewhere.

[5614]

sorry dont follow drz, do u mean, instead of making a transformer... use one, in a current electrical item, such as a phone.

 

well yes, that would be an idea, except that then you cant use the fone again,

 

it will be an ac voltage, not dc, but that doesnt matter really, for a light bulb.

 

but yes, you could use a pre-made transformer. nice idea!

[drz]

well, also, if you follow the site I linked to it shows a wide variety of "wall transformers" availible. The name of such a device escaped me at the time of my last post, which is why I mentioned the telephone. I'm sure there are some availible for ac applications as well.

[5614]

I'm sure there are some availible for ac applications as well.

 

all transformers work on AC, thats the only way they work, DC transformers are impossible, they dont work! however, after the input voltage has been transformed, it can then be transferred from AC to DC, in one of several methods

[drz]

i meant ac output

[5614]

ok,

most old transformers have an AC output, however, now-a-days, its 50/50 AC/DC outputs, probably because it was harder to change AC to DC in the "old" days!

[Lance]

He said AC applications not transformers. And most transformers are rectified but it would be easy just to tear the diodes out.

[Lance]

Also I don’t see why you don’t just go to a dumpster (or your garage) and find a suitable transformer. If you know what they look like there are tons of them everywhere. Although you would never find one rated at 8 or 10 amps or whatever you wanted.

[pulkit]

He said AC applications not transformers. And most transformers are rectified but it would be easy just to tear the diodes out.

 

Rectified output won't be good enough for a DC application.

You would need more than just a simple 2/4 diode rectifier, a more complicated filter circuit would probably be involved. I dunno how easy it'd be to detach that.

 

And yes, 8/10 amps seems to be a huge current requirement to run a bulb.

[YT2095]

all transformers work on AC, thats the only way they work, DC transformers are impossible, they dont work! however, after the input voltage has been transformed, it can then be transferred from AC to DC, in one of several methods

Hmmm... I hate to be seemingly "picky", but that statement`s not entirely true.

Pulsed DC transformers work perfectly well and can even out perform AC types when Frequency matched

[5614]

Hmmm... I hate to be seemingly "picky"' date=' but that statement`s not entirely true.

Pulsed DC transformers work perfectly well and can even out perform AC types when Frequency matched [/quote']

 

 

well, i agree, you are being "picky"

 

but you are right

 

however a pulsed DC current acts similar to an AC current, in a way

and yes, it does work...

 

thanks!

 

rbewley, whats happening, have you done this? are you alive?! keep us informed please...

[rbewley]

Well, thanks for all your help with this, I've actually made an induction coil and did some pretty cool things, but unfortunately, my lightbulb still does not work.

 

Since a transformer would be for AC, I'd have to use the mains, and using the mains to power my lightbulb would defeat the point, as the lightbulb needs 120V and it's already at that. I really wanted to get my DC batteries to power my lightbulb, so would I need to construct a transformer with a pulse DC current? If so, can anyone point me in the right direction of doing so?

 

And, actually it makes sense with the pulse, because if the magnetic field isn't changing, then it's not going to produce a current on the other side, just like putting a magnet that's sitting completely still inside of some coil, it's not going to generate a current either without some movement...

 

Thanks,

Richard

[5614]

has it ever occured to you that your light bulb may be broken? or that you may be connecting the leads to the wrong place. i think that your bulb should have at least glowed a bit by now, dimly, but you would have noticed it! try screwing it into a real light thing in your house/flat wtvr, and seeing if it works!

 

http://www.scienceforums.net/forums/showthread.php?goto=newpost&t=5509

 

is a bit about dc --> ac

 

alternatively you could use a 555 timer chip, which creates a pulse, look it up on the internet, its a pretty simple chip

[pulkit]

alternatively you could use a 555 timer chip, which creates a pulse, look it up on the internet, its a pretty simple chip

 

I used that recently, very handy indeed, small 8-pin IC

[5614]

yes, and you can get more than one pin to produce the output somehow, i did it whilsts experimenting, and easy and simple chip i found!

[vrkelley]

I have a similar question for a bicycle light.

 

a. With a 18V bulb how can I attach a 24V (.6AM) LED tail light to the back of the bike?

 

b. Do I need some sort of voltage regulator/transformer so the battery can last longer? If so which one?

 

18V

bulb >--------18V drill battery -----<24V LED tail light?

 

-Virginia

[pulkit]

What battery do you have ?

A 24V supply or 18V ?

[vrkelley]

The battery is 18V. I built another similar light with just the 18V bulb and battery and it worked cool. Now I want to add that 24V (.6amp) LED for a tail light.

 

Any suggestions?

[5614]

one sec; you want to power your 24V bulb with a 18V battery?

 

if so it wont work because transformers only work with AC and a battery is DC, all batteries are DC. therefore you would need to pulse the circuit, so probably use a 555 timer chip, read back over the past few pages of this thread for ways of pulsing the circuit. once the circuit is pulsed you can then use it in a transformer as, ONE SEC, this isnt to vrkelly, but everyone else......

 

if you use a batter --> 555 IC chip --> transformer, it still wont work, because transformers use AC, alternating, ac current is going back/forward, whereas a 555 timer makes a pulse, which is on/off all in one direction, so does a pulsed current work on a transformer????

 

if it does, then vrkelly, your light may work, if not then i dont think you can turn your DC battery into AC, in which case you cant make a transformer for it, in which case i dont think you can increase its Voltage. so why dont you just buy a bigger battery, or get a bulb which works on a lower voltage. you can get low voltage ultra-bright bulbs, they are normally used for bicycles, im suprised yours is 24V thats a lot! or it is a for a cycle light anyway.