Using a Common mode Choke (differential) as a joule thief transformer (working)

Almost any switch mode power supply has one of these chokes for noise suppression.  The type pictured below is the type that has been tested working.

The prewound choke Coil has even windings on both sides and uses many turns of thick wire around a ferrite core.
Using the standard Joule Thief configuration, it has been tested with a BD139 transistor, 1.4K Ohm Feedback Resistor and a Blue LED.
Starts up easily at 0.6V DC. and is much brighter than the standard joule thief at 1.5 Volts.

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Creating cheap custom power transformers by reusing a microwave oven transformer

Microwave oven transformers can easily be found discarded and reused to make a powerful custom transformer.  The ability to easily reuse the transformer comes from the primary and secondary windings being physically isolated from each other on the metal core.

The aim is to remove the secondary windings as cleanly as possible and wind a custom winding using enameled wire.  In my case for every one loop around the core gets one volt, the thicker the wire, the more current that can be supplied.

There are three windings on a microwave transformer, one primary and two secondaries.  In the pictures below, the primary is on the bottom and the secondaries are on the top.
The primary has hundreds of turns of thicker wire, do not modify this, keep it pristine.
The high voltage secondary, with thousands of turns of fine wire, we do not need this.
The six volt filament winding made from cloth insulated wire, we do not need this.

Removing the secondary is relatively easy. 

  • Clamp the transformer in a vice and using a hacksaw, cut one end of the secondary off.  Be careful that the saw does not cut into the primary at the end and try to avoid cutting the paper inner paper insulator.
  • Spray penetrating oil into the exposed wire in the transformer, this will help in the next stage.
  • Using a large drift and hammer, bash out the rest of the wire a bit from both sides at a time until it comes out like a horseshoe.  If the drift is too small, it will compress the wire and make it impossible to remove easily.
  • Once removed, clean all metal filings and make sure that the mylar paper insulator is intact, repair using insulating tape if required.  You do not want exposed metal cutting into the wire while winding.
  • Now using enameled wire, rewind to your own specifications.  The image below is a 4 volt ugly monster with several windings in parallel.

Remember that this transformer will hum like a microwave when in use.  It will draw lots of power. 
It will require some kind of forced air cooling to keep it happy.  Reuse the microwave fan…
Don’t attempt to take the laminations apart.  They are often welded. 
Best to source a transformer from a larger microwave oven, bigger = more power.

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Reclaiming space taken by plugpacks

I was pissed off the other day with the plug pack from my WD USB hard drive taking up so much space.  This time it was not the body of the plugpack, but rather the adapter for the multiple clip-on plug for various countries.

The ‘ears’ on this device were much wider than expected and needed to be lopped.

Taking a pair of side-cutters to it, did the trick.

If I collect enough, I will make a necklace just like Dolpf from Universal Solider.

I’m all ears.

WindyCityTech Blogger
windywindycitytech wordpress

Reclaiming space taken by plugpacks

I was pissed off the other day with the plug pack from my WD USB hard drive taking up so much space.  This time it was not the body of the plugpack, but rather the adapter for the multiple clip-on plug for various countries.

The ‘ears’ on this device were much wider than expected and needed to be lopped.

Taking a pair of side-cutters to it, did the trick.

If I collect enough, I will make a necklace just like Dolpf from Universal Solider.

I’m all ears.

WindyCityTech Blogger
windywindycitytech wordpress