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Other stuff: I realised that the modulator doesn't have any fiber optic transmitter so I bought one from ebay and it works now perfectly with the controller. And a little criticism about the controller: the inner stabilizers (7824, 7809, 7805) are surrounded by the only heat sensitive elements, all the electrolytic capacitors without any space. More problem, that the 7805 is connected directly to the unstabilized 24V, so it's so hot, it burned my finger literally and I'm not sure how the 7824 will handle the current to the gate driver. I fixed a heatsink to the 7805 and 7824, but I think I should remove them from the PCB and attach all these to a large heatsink and wire them back to the PCB.
The original UD2 did suffer from the regulators getting quite hot. If I recall correctly, the 7809 was one of the hottest, dropping from 24V to 9V, and you are right that they are placed in-between the capacitors. As long as you're not maxing out to 40V input, the 24V regulator should be ok, However, I'd heat sink them to be safe. After all, this one one of the main reasons why I switched to a switching regulator design for my UD2.7 revision, where the 7824 and 7805 uses the main PCB as a heat sink and the 7809 is a switching regulator: . I've had no problems leaving the board on for a whole day in an enclosed box, so hopefully this has solved the regulator heating problem.
Registered Member #1521
Joined: Thu Jun 05 2008, 10:46AM
Location: Hungary
Posts: 128
I see, thanks for the reply.
I welded a frame for the box, which will contain almost everything of the system, the driver, primary circuit and the driving coil for the extra resonator (this is why it's so big). So basically the whole driver will be in a closed box and only 2 wires, or copper tubes needed to be connected to the resonators, plus the modulator and the mains cable of course. The sides and upper plate of the box must be made with some insulator material, as the driver coil will create a few hundred kV's between its ends and it also prevents capacitive currents flowing back to ground.
Registered Member #1521
Joined: Thu Jun 05 2008, 10:46AM
Location: Hungary
Posts: 128
A little update. I brought back my small NST powered model from the university, so I made a few pictures and a video. Video There are problems with the air core transformer as there is no insulation on the surface, but I'm going to add something to prevent these nasty sparks. 350W NST and the max spark lenght is 50cm. But more importantly, it shows that the whole system is usable without a secondary ground. Interestingly, the sparklenght depends way more on the spark gap, than the actual primary capacitance. I changed the capacitors two ways, +-30%, but there was no difference on the output (extremely low primary quality factor?), but when I changed the spark gap, spark grew way bigger immediately. The whole system is very sensitive to what happens in the spark gap, mostly the ON period, while the gap is in the conducting period.
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