TESLA TECHNOLOGY LOG >> 2003/10/7 << Started this log on Tetsuo. ASCII for compactness and portability, on Tetsuo 'cause Loki is often in use for gaming & whatnot at the moment. Attempted to take pictures of partially constructed tesla coil with /Digital Dreams/ Precision Mini Digital Camera. Disaster. the thing is almost brilliant, but needs an extra fiver's worth of internals to make it so. Also I couldn't get a good looking shot in my bedroom, as it was full of junk and the lighting sucks. >> 2003/10/8 << Stuck log up on internut (and why not?). Got a couple of sort of pictures (in /photos) of my coil. Unfortunatly, my little camera isn't up to the task and they're dead blurry. The coil is an offcut of blue water pipe,the sort the council puts in (or whoever runs the water pipes these days). Two reels of 1.4amp 1kV stranded equipment wire were wound about the top section of this, creating a nifty looking black and yellow bifilar winding. The idea is not only to half the resistance by placing the two coils in series, but also to give me a big bifilar transformer, should I ever feel like building a giant Blumlein bridge or something. Below this is the primary. Rather than the usual practice of a wide, conical winding (typically bare), i've gone for a multi layer winding of solid core conduit wire. This will be brought out to a terminal panel, to allow the coils to be switched in and out at whim for tuning. The primary is quite far below the secondary, to keep the coupling coefficiant low. My last coil (which I built for the pulsed power group in Strathclyde University was a traditional coil (antique varnished wire primary, copper strip from an old grid transformer, top stuff). I wanted to try something a bit different this time. The lowest coil, of only a few turns, is a tickler. I hope to be able to use this to both monitor the field in the coil and to provide feedback to a triggered spark gap, to improve syntony. Made a tertiary out of 221 turns of conduit wire on a cardboard tube which once held wrapping paper. Diameter is 1 5/8" and the length 24 1/2", giving an inductance of about 127.8 uH and a self capacitance of about 37.5 pF. (NR)^2 L (uH) = -------- 9R + 10H C (pF) = 0.29 L + 0.41 R + 1.94 (R^3 / L)^0.5 N=turns, R=radius, H=hight (both inches) (formulae from http://home.earthlink.net/~electronxlc/formulas.html) I'm not sure how accurate these are for such a long, thin coil, but given that I'm hoping for multiple resonant modes, simple resonance calculations are liable to be unhelpfull anyway. >> 2003/10/9 << I succumbed to temptation: assuming the coil will resonate normaly against its self capaciance, its natural frequency would be about 2.3 megacycles (somewhere between the medium wave & marine bands). With the sort of capacitance I'm looking at using, it should operate at about 90 kcps, which is where I was aiming at. >> 2003/10/10 << No work on Tesla gear today. Spent all day at work wrestling with jabberd and CPAN - very much not in the mood. Wrapped 11 turns of my conduit wire on a toilet roll tube and called it a day. I estimate that this little coil will resonate with a 2l irn-bru bottle leyden jar somewhere in the marine band, which I can pick up with my multiband receiver and no mucking about with bizzarely long coils. I should really make some bare wire coils for tuning purposes. >> 2003/10/20 << Haven't updated here in a while - been busy (drinking irn-bru, so I've got lots of Leyden jars). However, on Saturday, a small triumph: I managed to salvage four electromechanical counters and a big power supply from the gutted remains of a fruit machine. 7.5A at 38VDC, 7.5A at 12VDC & 5A at 48VAC. I had thought it just a transformer at first and was going to convert it into an HT supply for the coil, but it seems to be a propper filtered supply, so I think it best to keep it as is. The counters might make an inertial instrument (a "velocimeter", for measuring velocity in three dimentions) - I could feed them from a set of acceleration dependent pulse generators or something. >> 2003/10/26 << Woo-hoo! I just worked out how to make kedit talk to an FTP server! No more faffing arround with multiple versions of files.