Trash Demagnetizer

[Rabid Badger]

I was cleaning out the shed and came across an old EI core transformer. Since tinkering is more fun than cleaning I grabbed some scraps and made myself a demagnetizer.

It's pretty potent; my Kill-a-Watt says it runs at 160W, which is more than units that sell for $100. To test it out I ran some screwdrivers and pliers over a hard drive magnet until they were very magnetic. One pass over this thing and they wouldn't even pick up iron filings.

 

[acer66]

Very cool.

 

[foghorn1966]

Have to ask. What was the transformer from? Nice job on the housing & build.

 

[Rabid Badger]

I think it came out of a little amplifier that I gutted for the housing when I put my bench power supply together.

I just cut the welds and removed the "I" part of the core and the secondary windings. That left the primary winding and the "E" core which I just wired up with a power cord and a momentary switch.

I did think the housing came out nicely for such a quick and dirty project.

 

[pizza]

good ****.

might add some kind of strain relief on the power cord though.

 

[Rabid Badger]

good ****.

might add some kind of strain relief on the power cord though.

It's glued in place with a generous glob of adhesive. Not my first choice but my box'o'cords seems to have gone AWOL.

 

[American Locomotive]

Very cool! One thing though, 160W is quite a bit of power. Since the transformer isn't doing anything anymore, that means all that power is getting turned into heat. 160W being directly dumped into the copper windings will heat them very fast (especially the coils in the middle).

Keep the "on time" short!

 

[Rabid Badger]

Very cool! One thing though, 160W is quite a bit of power. Since the transformer isn't doing anything anymore, that means all that power is getting turned into heat. 160W being directly dumped into the copper windings will heat them very fast (especially the coils in the middle).

Keep the "on time" short!

Yeah, I taped a thermocouple to the windings and they heat up an average of 7 degrees F per tool demagnetized. I doubt I'll ever need to do more than 2-3 at a time so there should be plenty of safety margin.

 

[Rabid Badger]

I suppose I shouldn't have posted a project like this without stressing the importance of testing and characterization.

When working with inductive loads it's important to have a device like a Kill-A-Watt that can measure actual wattage rather than VA.

Also temperature characterization is critical, especially if your housing is flammable.

 

[mc4life27]

Nice and I’m sure that’s way more powerful then the one I use. I got mine from my moms friend. Think I could find another one at a record store? O wait record stores are
Gone for the most part let alone any that sells accessories for tapes. O wait who even uses cassette tapes to record on any more lol.


Sent from my iPhone using Garage Journal

 

[Rabid Badger]

That thing says it pulls 5 amps at 117 volts. Assuming a power factor similar to mine that would be around 195W.