Hi, 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? Thank you Saul
how to separate ground potential
Started by ●October 16, 2008
Reply by ●October 16, 20082008-10-16
"Saul Bernstein" <jiffylube@freenet.de> wrote in message news:48f6e1b8$0$6569$9b4e6d93@newsspool4.arcor-online.net...> Hi, > > 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?Sure. Feed it AC and use an isolation transformer. Might have to get one special-made to withstand that sort of potential difference. Watch for safety regs. Rectify/regulate on-board. Bob M.
Reply by ●October 16, 20082008-10-16
Saul Bernstein wrote:> Hi, > > 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? > > Thank you > > Saul > >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.
Reply by ●October 16, 20082008-10-16
On Thu, 16 Oct 2008 08:40:17 +0200, "Saul Bernstein" <jiffylube@freenet.de> wrote:>Hi, > >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?--- Will the PCB be connected to anything other than the high voltage supply positive and the 220V mains? JF
Reply by ●October 16, 20082008-10-16
On Thu, 16 Oct 2008 08:40:17 +0200, "Saul Bernstein" <jiffylube@freenet.de> wrote:>Hi, > >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?--- If you need your +5V to ride on the high voltage, you could do it like this: (View in Courier) +--------------------------------------+ | PCB | | 7805 | | +----+ +-----+ | 220AC>-----+-----+ +--|~ +|-----+-----| |--+5V | | | P||S | | |+ +--+--+ | | | R||E | | [BFC] | | | | I||C | | | | | 220AC>---+-|-----+ +--|~ -|-----+--------+-----GND | | | | +----+ | | | | | | | | | +----------------------------|---------+ | | | | | | | | | | | +------+ | | +------------------|~ +HV|-----+---> | | | +--------------------|~ -HV|---------> +------+ You'll need a transformer with high isolation, and if your high voltage is 4kV I'd recommend a dielectric strength of at least 5kV from secondary to primary and from secondary to core. More would be better. Be aware that this is a dangerous circuit and you could easily get hurt or killed, or cause someone else to get hurt or killed JF
Reply by ●October 16, 20082008-10-16
On Thu, 16 Oct 2008 08:40:17 +0200, "Saul Bernstein" <jiffylube@freenet.de> wrote:>Hi, > >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? >You haven't indicated the voltage and power requirement for this housekeeping supply. At lower power levels, some simple self-constructed solutions are possible. RL
Reply by ●October 16, 20082008-10-16
On Thu, 16 Oct 2008 15:16:56 -0500, John Fields <jfields@austininstruments.com> wrote:>On Thu, 16 Oct 2008 08:40:17 +0200, "Saul Bernstein" ><jiffylube@freenet.de> wrote: > >>Hi, >> >>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? > >--- >If you need your +5V to ride on the high voltage, you could do it like >this: (View in Courier) > > +--------------------------------------+ > | PCB | > | 7805 | > | +----+ +-----+ | >220AC>-----+-----+ +--|~ +|-----+-----| |--+5V | > | | P||S | | |+ +--+--+ | > | | R||E | | [BFC] | | > | | I||C | | | | | >220AC>---+-|-----+ +--|~ -|-----+--------+-----GND | > | | | +----+ | | > | | | | | > | | +----------------------------|---------+ > | | | > | | | > | | | > | | +------+ | > | +------------------|~ +HV|-----+---> > | | | > +--------------------|~ -HV|---------> > +------+ > >You'll need a transformer with high isolation, and if your high voltage >is 4kV I'd recommend a dielectric strength of at least 5kV from >secondary to primary and from secondary to core. More would be better. > >Be aware that this is a dangerous circuit and you could easily get hurt >or killed, or cause someone else to get hurt or killed--- Oops... I'd intended for that to be held in abeyance until the OP replied with an answer as to whether or not there were only the two mains connections and the connection to the HV connected galvanically into the PCB, but somehow it slipped out. Phil nailed it as well. JF
Reply by ●October 17, 20082008-10-17
On Thu, 16 Oct 2008 17:49:25 -0400, legg <legg@nospam.magma.ca> wrote:> >You haven't indicated the voltage and power requirement for this >housekeeping supply. > >At lower power levels, some simple self-constructed solutions are >possible.At very low power levels, just send optical power up on an optical fiber and the data down on an other fiber. This system is used on some high voltage measurement instruments hanging on an overhead high voltage line. Paul
Reply by ●October 17, 20082008-10-17
Paul Keinanen wrote:> On Thu, 16 Oct 2008 17:49:25 -0400, legg <legg@nospam.magma.ca> wrote: > > >>You haven't indicated the voltage and power requirement for this >>housekeeping supply. >> >>At lower power levels, some simple self-constructed solutions are >>possible. > > > At very low power levels, just send optical power up on an optical > fiber and the data down on an other fiber. > > This system is used on some high voltage measurement instruments > hanging on an overhead high voltage line. > > Paul >Thats an interesting technique I've been hearing a little about lately. Whats state of the art for power over fiber? How big a laser does one need for how many mW at the remote end? Got any good links? Thanks. Ian.
Reply by ●October 17, 20082008-10-17
On Fri, 17 Oct 2008 07:36:36 +0100, IanM <Invalid@totally.invalid> wrote:>Paul Keinanen wrote: >> On Thu, 16 Oct 2008 17:49:25 -0400, legg <legg@nospam.magma.ca> wrote: >> >> >>>You haven't indicated the voltage and power requirement for this >>>housekeeping supply. >>> >>>At lower power levels, some simple self-constructed solutions are >>>possible. >> >> >> At very low power levels, just send optical power up on an optical >> fiber and the data down on an other fiber. >> >> This system is used on some high voltage measurement instruments >> hanging on an overhead high voltage line. >> >> Paul >> >Thats an interesting technique I've been hearing a little about lately. > >Whats state of the art for power over fiber? How big a laser does one >need for how many mW at the remote end? Got any good links?Do a Google search such as "optically powered" "current transformer" should give some useful links. For instance http://homepage.ufp.pt/alobo/page8/page5/files/IEEE%20PPT%20Conf2001_2.pdf describe a 300 mW laser at 810 nm and a photocell efficiency of 40 %, so you would get about 100 mW of usable DC power for the sensor and the optical transmitter to send back the information. Paul
