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Re: build your own magnet charger


 :
11/7/2005 7:45 PM
Joe Gwinn
Re: build your own magnet charger
On 11/7/2005 8:07 PM, DoctorX said:  
[QUOTE]If you took a large photo flash unit and fed the output into a set of coils and holding fixture, could that be used as a magnet charger? Also, since the better photoflash units have adjustable outputs, could that feature be used to "dial in" the amount of energy you would use to magnetize AlNiCo? Custom magnetizations per pole, maybe?  
 
Please note I am not talking about the photoflash units that sit on top of a 35 mm camera. I am referring to the types the pros use for studio work. The great big heavy bastards used to fire off large Xenon flash tubes.[/QUOTE]This can work, but with one change: The xenon flash tube is essential, as it acts as the switch that controls when the flash happens, as well as making the flash. The standard circuit has the flashtube across a humongous electrolytic capacitor charged to at least 350 volts. The xenon in the tube is un-ionized, and so no current flows. When it's time for the flash, the trigger transformer puts about 10,000 volts on the trigger electrode, that thin wire wrapped around the flashtube. This partly ionizes the xenon, allowing 350 volts to arc over. And the rest is history, the next millisecond or so.  
 
So, put the magnet charging coil in series with the xenon tube. And stay well away from it while firing the flash and magnetic pulse.  

 
quote:
"Just another nightmarish idea....."
I would submit that anyone not quite well versed in electonic things should not attempt this project. A sufficiently large capacitor at 350-400 volts is quite capable of killing the unlucky. A datapoint: A defibrillator delivers about the same amount of energy as a big photoflash, about 400 watt-seconds.  
 
For those who want to understand flash circuits, the classic book is "Electronic Flash/Strobe" by Harold E. Edgerton, The MIT Press, 1979. Also available in paperback. Professor Edgerton invented the electronic flash, I think around the 1920s.  
 
The design must be such that the voltage on the flash capacitor is never reversed, as electrolytics really don't like reverse polarity. This requires damping resistors along with the added inductance of the magnet charging coil. This is discussed by Edgerton.

 

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