The Turn Of The Century Electrotherapy Museum http://www.electrotherapymuseum.com Poulsen / Duddell "Singing Arc" Powered Tesla Coil Experiments I wanted to build one of these years ago - a decade or more - I recall early discussions with "Bill The Arcstarter" from the Tesla list, and David Quinlan, who built a working Poulsen Arc.  I have unfortunately lost contact with both people...any ideas as to where they are to share these experiments with would be greatly appreciated. This initial crude test was made on the floor with components that were handy.  An electromagnet for inductance, a diode from a welder (I also did the same experiments with a full-wave rectifier, but since the large aluminum heats take up so much floor space for this initial bit on the site I am half-wave rectifying it to keep it simple), capacitor from a microwave oven, electromagnet, homemade arc gap, small alcohol burner (brass tube with cotton dipped in alcohol as a small spirit lamp), Pancake Coil. I found it much easier to work with 240V than 120V, so I used a small transformer (actually a ballast from a 175W Mercury Vapour lamp).  I am sure a small industrial control transformer with a 480V tap would really do the trick, but 240V works really well. ..."In this form of break [Fig. 33], I changed the atmosphere in which the arc was operating.  The atmosphere was mostly hydrogen, and with this device I was performing my experiments before the Franklin Institute in Philadelphia and the National Electric Light Association in St. Louis.  This has been used by Poulsen and it is now the "Poulsen system".  But of course, there is no invention in it. I am on record in prior publications, and besides, the hydrogen does not have any other effect that it lowers the tension under which the device can operate.  It has the disadvantage of producing asymmetrical or distorted waves, and the impulses obtained are not best suited for tuning."                  Nikola Tesla, On His Work With Alternate Currents, Leland I. Andersen, Twenty First Century Books T. C. Martin book extracts "Singing Arc And Spark" test apparatus.  The lack of input current here (and crude magnet setup) hides the normal "squealing" of high current arcs and magnetic fields...but the oscillation part works fine!!  Note the arc gap is submerged under alcohol flame Hot short spark from Tesla Coil CLICK HERE FOR A MOVIE! Closeup of arc gap - I machined the parts from EDM graphite blocks and an old carbon arc electrode! Heavy Navy magnet, crude bolts to intensify the magnetic field around the arc.  A lot to improve upon, but starting off crude. Carbon Arc Gap...and Mejla.  Duddell used plain carbon electrodes.  I had to dig here, because most of my arc carbons are rare-earths filled for AC operation.  Everyone needs an arc lamp.  Be sure to check out Charles Brush's web site for more on those! "Food?" . . . More to come!!! 19. Dec - Modified Arc Gap - Copper-Carbon Gap. (In the style of Poulsen, copper positive, carbon negative) 20. Dec - More Tests, 10am - (Would have started earlier, but Mejla peed on the bed...at 2am.  4 loads of laundry later, I'm ready) Accidental shot with flash Appearance of sparks when operating smoothly Appearance of sparks when arc moves to a different part of the carbon - fluctuations. Typical appearance of arc gap Bubbling Alcohol, Cherry Red Copper, and Incandescing Carbon...no water-cooling yet, but it is still functioning even so hot! My alcohol burned is a cartridge shell, previously fired...turned on the lathe a bit.  Need to buy some wicks next...I was using a Q-tip! For these tests, I upped the capacitor to just under 2 mfd.  (2 Microwave Oven Caps) This time I opted out on the magnetic field.  I need to get some smaller magnets, rare earths or something similar! Not to mention some nice refractory material to replace the asbestos plate with.  I'm moving forward, reluctantly...