Im trying to craft a homemade transformer. I dont need any specific voltage/ current, Im just experimenting.

The problem im having, is that I just cant get my secondary coil to register any voltage at all.

Ive used both ferrite beads, and cylinders, and also steel rod as the core.
Im wrapping around the core a 36SWG copper enamled magnet wire.

No matter how many turns I do (primary or secondary), when I 'pulse' 9V through the primary, no voltage appears on the secondary!

If I repeat the same experiment with a proper salvaged transformer, the multimeter reads a brief voltage, as you would expect.

Does any one have any ideas where im going wrong?

Many thanks

 

Are you familiar with transformer theory? describe your setup exactly.

 

Maybe a voltage is induced but the meter isn't fast enough to see it. Best to look with a scope or apply AC voltage - very low of course ..

__________________
stevez

 

Im not to sure about transformers yet, just in the early stages of trying to understand.

My setup is:

I have tried tiny ferrite beads: i.e exactly as is described here, Appart from i used 36SWG enamled wire.

I have also tried steel rod with 50 turns each (primary and secondary)
however, i did not cut the steel rod to length (i.e about 0.5M to much!)

I have also tried ferrite rod, salvaged from a radio, This time i used standard stranded wire, 20 turns each.

All methods fail, but the 'proper' transformer that i salavaged works as expected!

Thats what i originally thought, however if I apply 9v to the salvaged transformer, the meter is quick enough to catch it.

I have tried pulsing with a 555 and transistor, but that didnt work either.


What can i be doing wrong?

thanks

 

You're mostly making RF transformers (high frequency ones), you need to be making LF (low frequency) ones. You need a laminated core, like from a mains transformer, and lots more windings.

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50 - 60 Hz transformers use soft iron not steel for their core.

 

Ok, but how come the Joule thief uses ferrite bead successfully?

 

hi,
The ferrite TXR's are run at a high frequency, the chances of seeing a 'kick' on your meter needle/or DVM, when you '9v' pulse the winding, are slight.

Make up a 555 10/100kHz osc driving a small power transistor, the transistor output drives the primary winding and a rectifier and smoothing cap are connected to the secondary winding, this should give a Vdc output across the cap.

If you want to avoid using an ext [555] osc, add a tertiary winding, to give positive feedback the base of the driver transistor, making it a self osc.

Eric

 

OP needs to read up on transformer theory.

 

Cheers eric,
I see what you mean now
The fact that i can see the single spike that occurs across the secondary coil in the salvaged transormer is because its core material is much lower freq (in a range that my multimeter can handle).

Sorry for being stupid, but do you think you could provide me with a circuit diagram of what you mean.

Also how many windings would you suggest for the feedback coil?

 

If you do erics suggestions, make sure your duty cycle / primary drive waveform is symmetrical so that you do not generate a DC component on the primary! If you do, your transformer will saturate and likely destroy your transistor driver. Transformers love perfect AC waveforms and hate anything with DC on it (even milli-volts of DC sometimes)

 

hi bitem,
Look at these links, they have blocking osc examples.

http://www.vias.org/eltransformers/l...ers_11_01.html
http://www.tpub.com/content/neets/14.../14181_132.htm
http://www.du.edu/~etuttle/electron/elect37.htm

Eric

 

ok cheers mate.