Powering my 40 watt light bulb

[5614]

Aren't transformers with multiple tap points kinda expensive ?

 

not really, ive got one, 3, 4.5, 5, 6, 9 or 12 V

 

[powered from the mains]

 

cost about £10 [uk money]

[pulkit]

[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...

 

So what does being equidistant have to do with it ? It'll have some some arbitrary expression for mutual inductance but transformer formula will still hold.

[pulkit]

cost about £10 [uk money]

 

You sure it has multiple points and not just a voltage divider ?

[5614]

to be honest, i dont know, just wondered, seemed a bit odd, thats all! a triangle! unusual, never seen nor heard of it before, so i wondered if it worked, thats all!

[5614]

You sure it has multiple points and not just a voltage divider ?

 

 

sorry, dont know how it works, just what it does, i know what the difference is, but i havent taken it apart to find out! probably a voltage divider, a guess, going on the fact that it is cheaper, but i cant say for sure.

[Guest Proxy-Cypher]

What effect does the gauge of wire used to make the coils have?

[Guest Proxy-Cypher]

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

 

 

While you are correct, I was hoping to discourage him completely - or even if not, he doesn't do any work anyways so it wouldn't be much of a loss

[pulkit]

It affects the non-ideal properties of the transformer.

Copper loss and stuff like that.

When you model a non-ideal transformer you also consider the capacitance and inductance of wires, this will b affected by the gauge.

[rbewley]

Should the wire be insulated? Especially if it is coiled around itself...

[pulkit]

If you insulate wires, you will affect their magnetic properties.

Most transformers would have this arrangement put away in a well insulated box, so that wires are still un-insulated but you don't kill yourself working with them.

The lead wires are made insulated for obvious reasons.

[rbewley]

Is it still ok to wrap the coils around themselves if my wire is uninsulated? The current won't "circumvent" the loop will it? Is it important that it actually goes through all the loops? I realize I may be rather vague in my question, but what I'm asking is... if all the uninsulated wires are wrapped around each other, will this cause a problem?

 

Thanks,

Richard

[pulkit]

Seems a bit of a problem.

What is generally done is that you wind in two different positions of metallic loop.

The loop is constructed not out of a one piece of metal but several insulated strips glued together. This nearly extinguishes all eddy currents and prevents this current "circumvention".

[YT2095]

this thread has gotten so full of crap since I last posted, it`s tempting to remove it!

 

and the crap about transformers is beyond belief!

 

for a start the shape DOES matter! think "Eddy currents"!!!

 

un-insulateted wires will NOT work!

 

the wire guage IS important as it effects the current (amperage) and can be offset by windings.

 

a bulb is neither an AC OR DC device!!!!!

 

and a variac is a semiconductor and NOT a transformer

 

 

*sigh*

[pulkit]

for a start the shape DOES matter! think "Eddy currents"!

 

As a standard practice, you would make your loop out of thin insulated strips pasted together, so shape can't matter. Eddy currents are out of the picture.

 

the wire guage IS important as it effects the current (amperage) and can be offset by windings

 

Wire gauge also affects circuit capacitance and inductance, which is particularly important to analyse a real transformer.

[YT2095]

the "E l" lamminates of soft steel or the layered toroids, are layered for a reason!

Eddys, the shapes is critical also for HT transformers or else you`ll get breakdown from corona discharge.

[Lance]

and a variac is a semiconductor and NOT a transformer

 

 

*sigh*

 

A Variac is a brand of autotransformer... I didn’t call it an autotransformer because the term Variac is more widely known...

 

Also... magnet wire is used for transformers, it won't look like there’s any insulation but there’s a thin coat of enamel on it.

[YT2095]

I`m all too familiar with "magnet wire" I`m a Coiler

 

btw, I misread and was thinking varactor the semiconductor (it`s an old term, probably not even used today, my goof).

 

either way, my points still stand

[Lance]

I`m all too familiar with "magnet wire" I`m a Coiler

 

Yes I realize that. It wasn’t really directed to you, It was directed to the people who thought magnet wire was not insulated.

[rbewley]

Well, thanks for everyone's help with this. Last question, assuming I'm using insulated wire to make my transformer, if I would like to make a step up transformer, how many loops do you think I would need for the following, and is there an easy formula for this? I understand it is ratios, but I'm not sure how to figure the primary side, any help would be appreciated.

 

Currently:

10 volts

8 amps

 

Thanks,

Richard

[rbewley]

Also as a side note, the wire I would be using is 18 gauge wiring.

 

Thanks,

Richard

[5614]

I understand it is ratios' date=' but I'm not sure how to figure the primary side, any help would be appreciated.

 

Currently:

10 volts

8 amps[/quote']

 

sorry, i dont really follow,

 

where is this 10V and 8A come from?

 

if that is your input, where is it coming from, [i ask as, transformers MUST be AC, and a battery is DC,]

 

maybe try V = IR

or: voltage = current X resistance

 

to work out the primary side, firstly, know your input voltage [transformers work on voltages] and then work what output volatge you want, then finally work out a sum to get from one voltage to the other,

 

e.g to half voltage. divide by 2,,, then put a random amount of wires in primary, say 50, then divide that by 2 as well, so you would have 25 coils on the output.

[Lance]

No, he wants 10V secondary but he doesn't know how many turns the primary should be.

[5614]

well, if you want a 10V output,

 

and your input it 240V,

 

then however many turns you put in the primary, divide by 24 for the secondary.

 

i think that any combination applying to the above rule is fine, just off the top of my head, i suggest: maybe:

 

well its hard to say really, because i dont know, if you can do 24 and 1, does that work as well as 100 and approx 4, i just dont know, try 24primary and 1secondary, and if it doesnt work just try doubling everything,

 

or wait till someone else here, answers the questing:

 

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?

[YT2095]

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

[5614]

yeah, or you could make a plug, transformer, and plug it all in, sounds simpler, doesnt it....

 

do you know the answer to the question i asked before your post?