Making A Magnet - Off topic

richard nineteenfortyone richard1941 at gmail.com
Mon Jul 21 14:47:21 MDT 2014


The goal is a wire fine enough to blow within 1/2 of an AC cycle.

On Sun, Jul 20, 2014 at 8:15 AM, Richard J. Nelson <rjnelsoncf at cox.net>
wrote:

> What an interesting idea.
>
>
>
> I will have to test this with known wire sizes.  Circuit breaker
> characteristics vary greatly and they don't respond very fast unless the
> current is many times their rating.  I wonder how long you could get away
> with, say, 100+ ampere current draws and I suspect it could be several AC
> cycles.  Certainly a piece of wire is much cheaper than using an actual
> fuse.
>
>
>
> Another thought is to use an NTC thermistor inrush current limiter.  They
> make some very low resistance (as low as 0.2 ohms) high energy values (30
> Jules) these days.
>
>
>
> My favorite way to make a magnet is to use an iron rod hanging on a
> string.  Orient it parallel with the earth's magnetic field (pointing to
> magnetic north - check where it is these days because it is moving 20 miles
> a year into Canada - and tilted slightly upwards if you are in the US - and
> then rapping it sharply with a hammer.  Presto, it is detectably magnetized.
>
>
>
> I use magnets a lot and I use a dozen magnetic tool holders.  My Philips
> head screwdrivers get magnetized all the time and I use a demagnetizer I
> made ten years ago as shown in the photo below.  The coil ID is 2-3/4" and
> it is very effective.  There is a transformer inside the old data cable
> switching cabinet.  The power switch is a spring loaded off type.  I have
> tried all kinds of demagnetizers and none of them are as effective as this
> one.  The coil is 14 Ga. house wiring and the turns were determined for
> maximum 2x current draw from the transformer.
>
>
>
>
>
>
>
>
>
> Perhaps I can use the same coil and add a switch to magnetize or
> demagnetize adding a small wire fuse holder/fixture as shown in the second
> photo.
>
>
>
>
>
>
>
> X < > Y,
>
>
>
> Richard
>
>
>
> -----Original Message-----
> From: hhc-bounces at lists.brouhaha.com [mailto:
> hhc-bounces at lists.brouhaha.com] On Behalf Of Richard
> Sent: Saturday, July 19, 2014 10:21 PM
> To: 'Handheld Computing Conference discussion list'
> Subject: RE: zapping NiCAD Cells
>
>
>
> You reminded me of the old procedure for magnetizing an iron bar.   Wrap it
>
> with heavy insulated wire, and wire it in series with a much finer wire
> that
>
> acts as a fuze.   Then plug it in.   Current rises as rapidly as the AC
>
> power waveform and the inductance will allow until the fine fuze wire
> blows.
>
> The current gets very high, more than enough saturate the iron bar beyond
> its magnetic capabilities.
>
>
>
> The fuze wire must be fine enough to blow in a small fraction of one cycle
> of the 60 Hz AC power.
>
>
>
> I tried this method when I was about 15.   My dad smelled the burned wire
>
> and came running in.   When he saw what I had done, he was really angry.
>
> But the house circuit breaker did not blow.   I guess my fine fuze wire was
>
> fine enough.
>
>
>
>
>
>
>
> -----Original Message-----
>
> From: hhc-bounces at lists.brouhaha.com [
> mailto:hhc-bounces at lists.brouhaha.com <hhc-bounces at lists.brouhaha.com>]
>
> On Behalf Of Roger Hill
>
> Sent: Sunday, July 13, 2014 9:51 PM
>
> To: Handheld Computing Conference discussion list
>
> Subject: Re: zapping NiCAD Cells
>
>
>
> Hi all,
>
>
>
> The capacitor method would undoubtedly be better, though my model train
> power supply did work every time for the cells in HP printer (or tape
> drive) battery pack.  I didn't aim for any particular amount of power
> applied.
>
>
>
> Actually, I do use a 3500-uf capacitor charged up to 30+ volts to operate
> the electromagnets used to throw the track switches on my model railroad
> layout.  The switch machines have coils designed to operate on 12-15 volts
> AC/DC, but by giving them a good "wallop" from the capacitor they are much
> more powerful, and because the pulse is very short, the coil is less likely
> to burn out (which could happen if a steady voltage is applied for too
> long).  I use relays and other capacitors to control the time (around 1
>
> second) for charging the main capacitor so that it is ready to throw
> another switch.
>
>
>
> Looks like the recommended procedure (below) is similar to my
> switch-throwing circuitry but with a bigger zap.  And agreed, the zapping
> procedure can effective for cells that won't hold their charge (due to
> shortage from internal conducting "whiskers" or filaments), but would
> probably not be effective from a cell that is weak for other reasons (or
> has too many whiskers).
>
>
>
> -- Roger
>
>
>
> ------------ On Richard N's messages ------------
>
>
>
> > The usual procedure is to charge a capacitor and discharge it into the
>
> > cell. This provides an energy controlled pulse.  Check the Internet
>
> > for UF values and voltages.
>
>
>
> > "To zap a NiCd battery, a 47,000mF capacitor is charged to 90V, after
>
> > which the raw power is discharged directly across a single NiCd cell
>
> > of 1.2V. After the shock treatment, the cell is cycled and then zapped
>
> > once more. Experts say that once a cell is treated and used in
>
> > service, zapping will no longer improve performance, nor does it
>
> > regenerate a weak cell."
>
>
>
> _______________________________________________
>
> HHC mailing list
>
> HHC at lists.brouhaha.com
>
> http://lists.brouhaha.com/mailman/listinfo/hhc
>
>
>
> _______________________________________________
>
> HHC mailing list
>
> HHC at lists.brouhaha.com
>
> http://lists.brouhaha.com/mailman/listinfo/hhc
>
> _______________________________________________
> HHC mailing list
> HHC at lists.brouhaha.com
> http://lists.brouhaha.com/mailman/listinfo/hhc
>



-- 
NOT sent from that galldurned iPhone with its crippled bluetooth and
authoritarian restrictions.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.brouhaha.com/pipermail/hhc/attachments/20140721/1ecc4ff6/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image002.jpg
Type: image/jpeg
Size: 43838 bytes
Desc: not available
URL: <http://lists.brouhaha.com/pipermail/hhc/attachments/20140721/1ecc4ff6/attachment-0002.jpg>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image006.jpg
Type: image/jpeg
Size: 71106 bytes
Desc: not available
URL: <http://lists.brouhaha.com/pipermail/hhc/attachments/20140721/1ecc4ff6/attachment-0003.jpg>


More information about the HHC mailing list