Introduction: My Small Transformer

Picture of My Small Transformer

this is my homemade transformer..i mean small...
its a transformer from a rc car charger...
i use ac adapter 12v...
i winding the primary coil(input)5 turn and in secondary coil(output)20 turn...
it is a e_block transformer...
i use ac adapter 12v as the input voltage...
i use 18v small pc fann...
its doesnt workk!!!!1
but why???
i hope u guys can help me solve thiss...
thanx you.....
one more...i want to make step up transformer.....
help me....


GaneshK24 (author)2017-04-12

I do not think so that a DC powered RPS would work . Becoz
chajgng current would produce magnetic flux which induces

chrismicro305 made it! (author)2016-12-23

Your transformer design is wrong. You need to wind both your coils en the center of the core and not on the outside. The way you winded it, it will never work, because the flux generated by the primary coil get lost in the center of your core and cant reach the secondary coil. You can wind the coils side by side or on top of each other. Then you need an AC supply connected to the primary and you will get AC out at the secondary. To drive the DC motor you need to connect a bridge rectifier in the AC output and a smoothing capacitor of about 3000 micro Farad between your positive and genitive. A good idea is to give your primary coil a center tap, that way you can use a two transistor oscillator to generate AC from any DC supply.

Lima79 (author)2016-11-24

i think i should start something like this instead of just blindly:P trying to make myself a 45-0-45 VAC which i failed twice miserably(:

shintashi (author)2016-04-11

when you plug in the DC adaptor to the wall, it has a transformer in it that is converting the wobbly goodness of polyphase AC wall current into the smooth non serrated butterknife uselessness of DC. When your butterknife current tries to saw through that meat transformer, nothing happens. You need wobbly goodness by either using AC directly, or by recreating AC from your DC. Engineering types will tell you all sorts of stuff, but basically, you need to turn your flat line (on the oscilloscope) into a series of serrated teeth. First they will get boxy with part 1 of the circuit, then the boxy shapes will get curved with part 2. I think it's kind of like acceleration vs. velocity. When you are traveling in an airplane, you don't notice how fast you are going until you change direction. Transformers are the same way - unless the voltage is constantly changing, it adapts and then ignores whatever voltage it is set to.

Here's another analogy: DC is like gravity, reliable, and always there, but to get a transformer to work, you need to make fake gravity, (fake AC), which is kind of like putting water in a bucket and spinning it around. The water doesn't fall out when the bucket is upside down because the water experiences fake gravity from the bucket. Scientists have fancy words to describe centripetal fake gravity, but even a 3 year old can keep the water from falling out, but it takes that extra step of spinning the water up and down in a circle. Pulse Width Modulation can probably do that. I dunno. I've only been studying electricity since March.

Haribalan (author)2016-02-11

hi.i just studied your your question.i didnt understand.

GabrielP11 (author)2016-01-17

Try to simulate and develop a functional circuit. It should help.

ahelm3 (author)2013-05-01

The Fan is DC and the input is AC. The transformer is going to output what the input is so an input of AC will yield AC output. DC input will yield DC output. You need some sort of converter to get dc into the transformer.

belangers (author)ahelm32015-10-06

A transformer will not operate on DC voltage, unless it is modified, pulsed, etc., however, the transformer is made to transform a clean sinewave, not a square wave, even though the square wave will make the transformer function, it will not function in the correct manner since the wave is not linear. The ac wall wort transformer must have an AC output, not DC... this is the first problem. Second, when you get the transformer to work, you will have to put a bridge rectifier on the output with a smoothing capacitor so the output voltage is a DC current, and, the voltage output spikes are absorbed to keep them around 18 volts and, the additional voltage spikes will be stored into the cap so it is released smoothly and at a lower voltage range spread out evenly to give the fan a smooth and steady DC voltage so the fan operates at the correct voltage without getting smoked from the higher voltage emf pulses.

ahelm3 (author)ahelm32013-05-01

Sorry the input has to be AC. Change the voltage to DC after the transformer with a converter.

SarathC1 (author)2015-06-20

Your set up is step down transformer so the ratio of voltages of the primary and secondary coils is equal to the inverse of the no of turns of primary and secondary so the voltage generated is 3volts so the 18 volt fan doesn't works and also the current is DC but not Ac

GokulkrishnanG (author)2015-04-23

i think the flux produced in primary is not completely linked with the secondary coil... try increasing the no. of windings in both primary and secodary... then give its output to a regulator and then to the fan...

rz1997 (author)2014-06-11

to induce current in secondary coil the primary coil should have A.C. input D.C will work only at the moment when u initially connect the +ve and -ve leads to the primary , it will not work after that (as in DC the current only fluctuates in the beginning when when u touch it to the leads of the primary .).

So a transformer requires AC input and WILL gives out AC output .

if u want to convert the AC output to DC use a bridge rectifier(search bridge rectifier on google ).

rundmcarlson (author)rz19972015-04-19

I know this is old, but if you use a transistor-transformer setup, you can rapidly turn the dc from nil to max repeatedly, creating a magnetic flux in the process. The voltage does not have to be traditional ac, it just has to vary. You certainly can do this with dc using a transistor, and if the frequency is high enough the fan will spin without you being able to notice that it isn't continuous. This is how joule thiefs work.

s.vishnuV (author)2014-12-30

all the below cmnts are wrong the reason is the output after step up will be AC and not DC.Theoretically only AC current can be stepped up.the a DC fan will not run on AC supply (author)2014-11-14

I am shocked are you crazy ? this small winding ! this shortcircuit the AC
adapter you are using . you need more lots of winging at primary atleast 10
ohm resistance okey baby

myfcr (author)2011-11-04

Your 12V ac adpater is giving 12V DC on the output

You CAN NOT put DC on a transformer and get DC transformed(what you are ding is just a electromagnet)

ARJOON (author)2010-08-20

your frequency is toooooo low

cam1128 (author)ARJOON2011-04-11

How do you make a 7.5 times step up DC transformer? (for 90V neons)

Thanks Cameron Dry

ARJOON (author)cam11282011-04-12

use a 555 timer. amplify with mosfet or a transistor through the transformer. rectify other end connect it to your load

cam1128 (author)ARJOON2011-04-14


musher95 (author)2010-07-20

ok thanx.... does anyone have pic like mine??i mean step up transformer thread or forum...

musher95 (author)2010-07-19

ooh..i got it.. thanx... so where to get the ac adapter.....

ironsmiter (author)musher952010-07-19

what gmoon said was not ENTIRELY correct, but from a basic, practical standpoint, it's close enough.(for short-term, cutting edge, supercooled DC transformer theory, consult your local Physics PHD, NASA engineer, or a really good theoretical physics text. AC transformers are just DC transformers that wildly swing their polarity to prevent heat and magnetic flux buildup in the ferrite core) AC adapters can be had at many electronics stores(normal retail and surplus) you could also crack open the one you have, and re-wind the transformer inside IT, to get your correct voltage. If you make your own step up transformer, and use an AC adapter, don't forget to rectify the voltage before feeding it into the fan. 18VAC probably will not work with that style fan. If you choose to work with what you have, after cracking the plastic case of the power supply open, you should clearly see the transformer that needs rewiring. As always, your warrenty on ALL parts is now void, but it sure was fun wasn't it?

gmoon (author)ironsmiter2010-07-19

Ironsmitter: reference please, especially how a typical inductively coupled transformer is just an offshoot of something called a "DC transformer."

Yes, my comment was intentionally simplified.

But inductive coupling only happens with change in magnetic flux. With DC, the only energy transfer to the secondary happens when the current is applied or removed.

Faraday's law of induction:
The induced electromotive force or EMF in any closed circuit is equal to the time rate of change of the magnetic flux through the circuit.

After the initial inrush current, an inductor with DC applied is basically a resistor (with an EM field). Inductors are essentially the opposite of capacitors: they pass low frequency current easily, tend to resist higher frequencies. Caps pass high freq easily, tend to resist lower freq...

Lets not stray into subatomic physics, or supercooled magnets, since that's not gonna help the OP.

ironsmiter (author)gmoon2010-07-19


I completely agree that we shouldn't stray into the area normally described as "significantly complex as to appear as magic" area here. Unfortunately the reply box chose to eliminate paragraph breaks so THAT part of my comment probably came out looking a lot snarkier than it was. Mea culpa.

You did hit the nail on the head though, when it comes to how the "dc transformer" works. To quote your succinct explanation of how it works, "inductive coupling only happens with change in magnetic flux. With DC, the only energy transfer to the secondary happens when the current is applied or removed." As long as you continue to supply the DC current, and can keep your core from saturating magnetically and thermally, you can continue to add energy to the primary, and extract it from the secondary.
The practical limitations obviously being the core. That's where the NASA engineers and PHDs come in. Material engineering.

I'm thinking though, if this comment doesn't satisfy your curiosity, we should move the comment thread to the forums :-) when we start using phrases like "flux capacitance" then suddenly people will think we're nuts, instead of just using proper technical jargon. Just gotta love when science-fiction and science fact overlap. :-)

gmoon (author)ironsmiter2010-07-19

( had to reposted this--it somehow got bumped to the top, even though I replied in the tread...things is messed up here today. Can't view my own projects...)

Dude, I totally enjoy your tone. I'm never looking for a fight. Conflict on the web is pervasive, petty, and consequently really boring. ;-)

Unfortunately, you gotta go back to school on this one. No current is induced in a coil unless the magnetic field is changing. Yes, you can induce current in a secondary by connecting DC--but it's induced only when you initially apply it OR when you remove the DC and allow the field to collapse.

But a steady DC voltage produces zero induction in a secondary coil. Yes, it produces a magnetic field, but induction requires a changing field.

I'll grant you--pulsed DC can do this as well as AC. Technically , you can't call even a sine wave "Alternating Current" unless it alternates both positive and negative, respective to some ground reference. But it's the change that really matters here, and most folks consider DC to be a continuous voltage...

It would be so awesome if a fixed magnetic field induced current. All the world's energy needs would be solved--just wrap coils around permanent magnets and draw off all the current we need! No work--infinite energy!

But that doesn't work, obviously. Generators require that either the magnets or the coils move --I.E., the changing EM field is what induces current in the coils...

Take this to the forum, if you like.

rimar2000 (author)musher952010-07-19

1) Five turns in the primary and twenty in secondary coil are too few. Try tenfold both, and performance will improve. 2) With these relations 1 to 4 (5 to 20, or 50 to 200) you will transform 12V AC to 60V AC. Your fan can burn if the transformer functions well. 3) To convert AC to DC you must use an diodes bridge. You can make it (it is easy) or buy it.

musher95 (author)2010-07-19

rimar200 n ironsmitter..thanx for the comment... okay.. actually i want to make a step up transformer... i just ripped my transformer from my rc car charger..(not in the pic..) what i found inside there is a transformer,diodes brigde ,capasitor... can i use 2 transformer..which mean 1st transformer without the diodes brigade or capasitor..that is directly from the ac(step down transformer)from 220v to 12v and connected secondary to the primary of second transformer (step up transformer)12v to **v......i upload the pic if u don understand what i mean.

ironsmiter (author)musher952010-07-19

If you are attempting to avoid the process of rewinding your power supply transformer...

Simple answer YES. The actual DOING can be a little fiddly, but sure you can do it that way. without too much trouble. The only real trouble you should run into is fitting the second transformer into the power supply case. If they're too close together, you can get magnetic field "bleed" between the two transformers.

I would still suggest de-soldering, rewinding, and re-inserting the main transformer into your power supply. That would probably be safest and fastest. Since you're going from 7.5V output to 12 volt fan... rewinding the secondary with an extra 50% turns of wire(If there's 10 turns now, rewind with 15 turns, etc.) should supply 11.5 volt. Close enough for almost any electronics.

I save this to last, because you have shown a certain comfort level doing this sort of thing already. So mainly, this is aimed at the crowd likely to sue when they land in the hospital.This is dealing with mains voltages. If you think holding live 110/220 wires in each hand might hurt, don't go here. Doing things badly can cause explosions, fire, and terminal electricity poisoning. Proceed with a healthy respect for the forces you are playing with.

gmoon (author)2010-07-19

If the AC adapter outputs DC then the transformer won't function.

Transformers, like all inductors, only work with a changing magnetic field--I.E., an alternating current supply.

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