POWER TRANSFORMER
- OBIT (oil burner ignition transformer)
- Uin = 220 V, 50 Hz
- Uout = 9500 Vef
- Iout = 23 mAef
- P = 220 VA
- no protection
- the resonant cap calculated = 7.71 nF
SECONDARY COIL
Searching the web I observed that big secondaries don;'t fit well with OBITs for a
good spark output, so I chosed a smaller diameter, short secondary trying to match
with the power level and the expected streamer output.
- grey PVC pipe sanded and wax coated
- diameter = 5 cm = 1.96 inches
- total lenght = 27 cm = 10.62 inches
- wound lenght = 23.5 cm = 9.25 inches
- D/L = 1/4.7
- end plasticine caps
- N = 1175 turns with 0.2 mm magnet wire
- no varnish
- calculated inductance = 13086.778 uH
- calculated self capacitance = 3.7031 pF
TOPLOAD
- little toroid made with a little wheel envelope covered with alu foil
- cross section diameter = 5.73 cm = 2.25 inches
- outer diameter = 19.7 cm = 7.75 inches
- calculated capacitance = 8.5524 pF
RESONANT FREQUENCY = 437.61 kHz
PRIMARY COIL
- flat pie coil, wound on a 30 cm diameter wooden support
- N = 10.5 turns with bare copper wire with 10 mm^2 cross section
- inner diameter = 7 cm = 2.75 inches
- outer diameter = 28 cm = 11.02 inches
- tap at 9-th turn
- calculated primary inductance at 9 turns = 19.51 uH
- 1 cm distance between inner turn and the secondary
- the bottom turn of the secondary at the same level as the primary inner turn
PRIMARY CAP
The resonant cap calcul;ated for this OBIT is 7.71 nF. I tryed first with a LTR (larger than resonant) approach, but the sparks were not very long and the gap didn't sound right. For low power systems I'll better go with a lower than resonant primary cap
(good BPS for streamer grow)
- 6.66 nF @ 24 kV MMC
- made with 15 x 100 nF @ 1600 V poplipropilene caps in serie
- the cap is located under the primary support, kept in place with nylon ties
SPARK GAP
- double, variable gap made with 3 aluminium heatsinks. The moving heatsink is placed
on a plastic ruler, kept in position by wooden leaders glued on the base.
GROUNDING: house water pipe
MAINS: no variac used
RESULTS: 9-10 inches streamers with hits up to 11 inches
NEXT STEP: bigger, smoother toroid, new gap design for 14-16 inches output.
RESULTS: 16 inches sparks with a bigger toroid and more gaps.
Hey, I am at the plug, while Costy make some pics....... This is real time pic, not double exposure!
- bigger old toroid, with a "special nail"
- cross diameter = 8.5 cm
- outer diameter = 27.3 cm
- calculated capacitance = 11.77 pF
- 4 gaps for the spark gap (with two more fittings for water pipe)
Works as a charm!
I used two things mentionated by Gary Lau on his page:
"There are two important tricks necessary to extract the longest streamers to a grounded target.
First the tip of the breakout point on the side of the toroid is critical. It must not be a point, but rather a sphere. A rounded arc of 14 gauge wire was too small and a 1.75" diameter spherical doorknob was too big. Best results were had with a 1/2" brass sphere.
Second the strike target is critical. I had using a basement lally column and a basement foundation wall, but the best I could extract was 12 inches strikes. I later noticed that using a chicken wire covered Faraday cage (of Death) as a target at the RATCBA teslathon, I was able to better my 12 inches record by 2". And I have since reproduced the results at home, using small sheet of plywood, covered with chicken wire."
The target is an alu foil screen.
Next goal: new gap for 20-21 inches sparks.
RESULTS: 20-21 inches discharges with a new multiple gap.
- made with 6 steel water pipe fittings, on a veroboard with copper surfaces removed. The electrodes are kept in position by crocodile clips.
Easy to adjust, remove and clean.
