Hello!
I am thinking a making the most basic transformer possible as an experiment. But first, I want to find out if it is possible or not. I have a small cardboard tube and some magnum wire. I make 100 coils of wire on the tube, and secure it with clear tape. Then, I make 50 coils on top of the first coil separate wire, and secure that. If I power my primary coil of 100 coils with an oscillating DC current of 9V, will 4.5V be generated in the second coil (step down transformer)? I the 50-coil is used as primary instead, will the voltage be stepped up to 18V?
Thanks!
with an oscillating DC current...
In that case, it wouldn't be DC. 
You can run a square-wave through a transformer, but you normally don't get a square wave out of the secondary.
You may be able to make something that "works", but it's not easy to make a efficient-usable transformer.
With 100 turns, you won't have much inductance and the DC resistance will be low. At low frequencies (say 50Hz or 60Hz power-line frequency) you'll get too much current through the primary coil. If you have a high-frequency oscillator, you could experiment with something like that, but it would still be a good idea to limit the current, especially if you don't have a way of measuring inductance. (If you limit the current, you also be limiting the voltage.)
If you want to make a transformer, I'd suggest winding your coils around a bolt or iron rod. You'll still have to limit your current (at lower frequencies), but you could probaby measure the step-up voltage (with no load). Maybe at a frequency of 100kHz, you could get useful results but that's just a wild guess and I don't know.
Why not answer your own question by trying it? That's the whole idea behind an experiment ---
Build an electric transformer (DIY)
RoyK:
Why not answer your own question by trying it? That's the whole idea behind an experiment ---
At this time, I don't have magnum wire. I also want a bit of background information (as DVDdoug provided), so I know if it is worth it or not. Also, instead of an iron bolt, can I use the cardboard tube wrapped in aluminum tape instead? Also, the YouTube video was a good tutorial, but not a "most simple" one. By "simple", I mean that it only needs the most basic principle of a transformer, and can produce voltage in the secondary coil.
Iron will work best - need something ferrous.
Got any big nails laying around? That would work.
What is the role of the iron?
What is the role of the iron?
If you ask that question then you haven't bothered to do much if any research on how a transformer works. Ten minutes reading this single google result for "transformer" will be worth your time.
The diagrams show a square of iron. How would I do it with a large nail?
Wrap both windings around the nail. Might be tricky if the nail is small. Try an iron bolt. Or go buy a ferrite core from your electronics supplier.
Wrap both windings around the nail.
Side by side, primary on top of secondary or secondary on top of primary?
I'm not Mr Transformer Expert, but I would have experimented with wrapping either the primary or secondary first, and then the other one on top of it. The idea of the nail (iron) is to help with the magnetic flux in a way that the Wikipedia article explains. This image for example suggests they are on top of each other:
(Attribution: File:Transformer-hightolow smaller.jpg - Wikipedia )
If I was experimenting, I would try various permutations and see which one works the best. It probably varies by frequency, amongst other things.
DVDdoug:
with an oscillating DC current...
In that case, it wouldn't be DC.
That's precisely what you should get, the same voltage waveform out, since the same flux change links
the two windings (for an efficient transformer).
Of course an air-cored transformer will not be efficient since the flux linkage is far from 100% (except for
bifilar wound transformers).
Once you load the secondary you may get distortion of the waveform - that usually indicates that the
efficiency is varying between the frequencies of the various signal harmonics. A good pulse transformer
will keep waveshape when terminated correctly across a wide frequency range.
Without using a ferrite core you are unlikely to make a reasonable wideband transformer.
Your requirement;-
- 100 coils of wire
- an oscillating DC current of 9V
- step up
- step down
You could experiment wireless power supply module
Wireless Charging Module Couple-01 5V/600mA
Wireless Charging, elecfreaks.com, $7.90
Use ferrite core to increase efficiency, change coils of receiver and capacitor of receiver, may be replacing zener or power regulator for output voltage.
Iron will work best - need something ferrous.
I have a 0.9cm wide BBQ lighter tube that has about 11cm of space for the coils. I can attach magnets to the tube, meaning it is iron or steel. So, I'll just experiment with this for now. Thanks for all the info!