I have to design a printed circuit board for a high-voltage environment. Hence, the "ground potential" of the board has to be on 4 kV. Du to the fact that the absolute potential values don't matter, one could say that the 2 kV are virtually my ground potential. The problem arises by reason of the power supply. I have to power my board with 5 V and for the mains adapter ground is really 0 V.
Can someone think of a possibility to supply my board with a mains adapter (AC/DC 220V/5V) and translate between the two ground reference potentials?
Nobody wants to touch this query because if you dont know HV stuff pretty well, you *will* be incapable of safely implementing any suggestions.
The idea of using a pluggable adaptor is EXTREMELY DANGEROUS as any fault could lead to having 4 KV on the plug pins.
Its in the category: Make your will, pay for a funeral plan but dont bother with life insurance because they wont pay out for suicide.
BUY IN an isolated PSU rated for sufficiently more than your working voltage, Ground the case to the same ground as the HV source with a BOLTED on cable (not removable without tools). Have all the high voltage wiring hooked up by a qualified HV technician and you *may* stay out of that pine box. *DONT* order anything you haven't cleared with the technician.
Alternatively why not consider battery power? A SLA battery and a regulator could easily power most microcontroller circuits for a day's running then you'd shut down, isolate your circuit, unplug the battery and recharge it overnight with an off the shelf charger. No more risky than the rest of your board if the battery is in the same enclosure.
If you need to transfer data, use fibre optic cable or any sort of wireless link.
If this is an academic project you've just been given for ****s sake consult with your tutor, the senior departmental technician and the Prof. You *may* need another project if you are asking this sort of question here (sci.electronics.basics) and you want to pass the course.
The easy way to do this is probably to use an isolated DC-DC converter. A few kV of isolation is typical; I'm sure you can find ones with higher ratings if needed. If you do not have any circuitry whose ground potential needs to be at 0V then you can use an isolated switching power supply to go from mains current to a floating 5V output (this would be cheaper than a non-isolated supply followed by an isolated converter). The transformer in many power supply designs provides this kind of isolation "for free".
Wim Lewis , Seattle, WA, USA. PGP keyID 27F772C1
"We learn from history that we do not learn from history." -Hegel
6V (open circuit) GaAs photovoltaic diode. It looks like there would be no particular problem getting 15 mA at 3.3 V for a microcontroller or whatever. I suspect that it would be out of the price range of the average hobbyist but if one is building Van Der Graph generators or similar it might be justifiable.
Its a far cry from two minature PM DC motors coupled shaft to shaft with a couple of feet of Perspex rod in between :-)
At low powers and bad efficiencies, transformers to handle a 4KV isolation is fairly easy. At bigger power levels or efficiencies above 50% it gets harder fast.
What does this PCB have to do? How much power etc?
Does the PCB live inside a shield?
At low powers, the simplest design is to use an "air core" transformer with the primary and secondaries tuned and loose coupling between then because of the large clearance. The down side is that this tends to radiate a lot of RF at your operating frequency.
At least this mechanical system can be scaled to quite large power levels :-)
Other low power isolated power transmission systems include feeding acoustic vibrations into an isolating rod or using radio frequency power transmission (after all the isolation distance required is only a few meters).
Yes this sort of thing can be done but you really should know what you are doing in the high voltage areas when doing projects like this. Some of the systems I work with have rails of 132kV DC (in the MW region) and this takes very special handling and checking from the design through the implementation to maintenance planning before we build such systems.
As many of the professional engineers here who would know this stuff and know of the dangers it is hardly surprising you are not getting much help without knowing your level of experience. It is an area that is at such a level that if you have to ask then you shouldn't be doing this without adequate oversight and supervision. The professionals will want to know that you have that in place and by asking here it is obvious that you probably haven't and it would be criminal for them to offer a solution.
Paul E. Bennett...............
This is the same sort of problem as electron microscopes (and even microwave ovens) have in driving the filament. The easy solution is to box up a 6V battery and regulate down to 5V. The commercial solution is a custom-made, tested, transformer that safely holds off 4 kV. It's likely to be potted (embedded in a blob of tar or silicone).
You don't want any of the 4kV parts outside a shielded and interlocked enclosure, of course...