115/230V voltage switch key for transformer?
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From: krw on 25 Nov 2009 13:35 On Wed, 25 Nov 2009 10:25:01 -0800, Joerg <invalid(a)invalid.invalid> wrote: >osr(a)uakron.edu wrote: >> Yeah, the ON circuit is crude, and the SCRs in series are a failure >> point. But its a start. >> And from a safety point of view, its got to be more of a hazard then a >> properly made jumper. >> Kinda my point. >> >> I take it this is on a linear for noise or cost reasons? >> > >Two reasons. The cost of transformers is remarkably low, around five >bucks for 10-15VA. Can't beat that with a switcher, even considering >your own PWM stuff behind it because that only adds a buck or two. > >Then, temperature. Beats me but all the places I've called won't endorse >more than 50C or 60C for their switcher modules and that's just not >going to fly. For some reason my own designs never had such limits but I >can't justify the NRE for all the agency testing on this one if we >rolled our own mains-connected switcher. > >The only 250V-rated selectors I see are panel mount and insanely >expensive, such as this one: > >http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=0033.1118-ND How about a wall wart? You should be able to find something like that for $10-$15.
From: Joerg on 25 Nov 2009 14:31 krw wrote: > On Wed, 25 Nov 2009 10:25:01 -0800, Joerg <invalid(a)invalid.invalid> > wrote: > >> osr(a)uakron.edu wrote: >>> Yeah, the ON circuit is crude, and the SCRs in series are a failure >>> point. But its a start. >>> And from a safety point of view, its got to be more of a hazard then a >>> properly made jumper. >>> Kinda my point. >>> >>> I take it this is on a linear for noise or cost reasons? >>> >> Two reasons. The cost of transformers is remarkably low, around five >> bucks for 10-15VA. Can't beat that with a switcher, even considering >> your own PWM stuff behind it because that only adds a buck or two. >> >> Then, temperature. Beats me but all the places I've called won't endorse >> more than 50C or 60C for their switcher modules and that's just not >> going to fly. For some reason my own designs never had such limits but I >> can't justify the NRE for all the agency testing on this one if we >> rolled our own mains-connected switcher. >> >> The only 250V-rated selectors I see are panel mount and insanely >> expensive, such as this one: >> >> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=0033.1118-ND > > > How about a wall wart? You should be able to find something like that > for $10-$15. The only way to get one in would be to snip the end off a two-prong Christmas extension code, solder it in and strap the whole kludge down with cable ties. Any fire marshall would blow a gasket ;-) Plus I think wall warts don't like to bake in there. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Rich Grise on 25 Nov 2009 15:16 On Wed, 25 Nov 2009 08:52:29 -0800, Joerg wrote: > petrus bitbyter wrote: >> >> Why a slide switch will not do? You can find voltage selector slide >> switches in which the slider is burried so deeply it can only be >> operated by a small screwdriver or something like that. Sliding it >> accidentaly seems next to impossible. >> > Not that easy anymore. Slide switches often don't have the respective > agency ratings and since they are primary side they must. Also, it is very > hard to find any that are rated 260V which is required for countries such > as the UK. Don't PC power supplies have these? If so, then _somebody_ is making millions of them, and they can't be terribly expensive. Another thing - if it's inside the case, (i.e., soldered to the PCB), couldn't you put a "No User-Sericeable Parts Inside" sticker, and just set an ordinary slide switch or jumper at the factory? I once worked at a battery charger manufacturer, and the boss had "designed" a circuit that would automatically switch, depending on what you plugged it into. - a relay, a diode, a cap and a couple of resistors. If you plugged it into 120, the relay didn't pull in, but if you plugged it into 240, the relay pulled in and switched the primaries. But that's a little parts-intensive, and you're not expecting pathological operating conditions, right? Thanks, Rich
From: Rich Grise on 25 Nov 2009 15:22 On Wed, 25 Nov 2009 11:31:18 -0800, Joerg wrote: > krw wrote: >> On Wed, 25 Nov 2009 10:25:01 -0800, Joerg <invalid(a)invalid.invalid> >>> osr(a)uakron.edu wrote: >>>> Yeah, the ON circuit is crude, and the SCRs in series are a failure >>>> point. But its a start. >>>> And from a safety point of view, its got to be more of a hazard then a >>>> properly made jumper. >>>> Kinda my point. >>>> >>>> I take it this is on a linear for noise or cost reasons? >>>> >>> Two reasons. The cost of transformers is remarkably low, around five >>> bucks for 10-15VA. Can't beat that with a switcher, even considering >>> your own PWM stuff behind it because that only adds a buck or two. >>> >>> Then, temperature. Beats me but all the places I've called won't >>> endorse more than 50C or 60C for their switcher modules and that's just >>> not going to fly. For some reason my own designs never had such limits >>> but I can't justify the NRE for all the agency testing on this one if >>> we rolled our own mains-connected switcher. >>> >>> The only 250V-rated selectors I see are panel mount and insanely >>> expensive, such as this one: >>> >>> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=0033.1118-ND >> >> How about a wall wart? You should be able to find something like that >> for $10-$15. > > The only way to get one in would be to snip the end off a two-prong > Christmas extension code, solder it in and strap the whole kludge down > with cable ties. Any fire marshall would blow a gasket ;-) > > Plus I think wall warts don't like to bake in there. What exactly is it you're trying to produce? You've given several different conflicting scenarios here. Is the user supposed to be responsible for selecting the voltage? Does it get set at the factory? What code are you trying to satisfy? Please, Joerg, tell us the "big picture" here. BTW, how do you pronounce "Joerg?" :-) Thanks, Rich
From: Joerg on 25 Nov 2009 15:34
Rich Grise wrote: > On Wed, 25 Nov 2009 11:31:18 -0800, Joerg wrote: >> krw wrote: >>> On Wed, 25 Nov 2009 10:25:01 -0800, Joerg <invalid(a)invalid.invalid> >>>> osr(a)uakron.edu wrote: >>>>> Yeah, the ON circuit is crude, and the SCRs in series are a failure >>>>> point. But its a start. >>>>> And from a safety point of view, its got to be more of a hazard then a >>>>> properly made jumper. >>>>> Kinda my point. >>>>> >>>>> I take it this is on a linear for noise or cost reasons? >>>>> >>>> Two reasons. The cost of transformers is remarkably low, around five >>>> bucks for 10-15VA. Can't beat that with a switcher, even considering >>>> your own PWM stuff behind it because that only adds a buck or two. >>>> >>>> Then, temperature. Beats me but all the places I've called won't >>>> endorse more than 50C or 60C for their switcher modules and that's just >>>> not going to fly. For some reason my own designs never had such limits >>>> but I can't justify the NRE for all the agency testing on this one if >>>> we rolled our own mains-connected switcher. >>>> >>>> The only 250V-rated selectors I see are panel mount and insanely >>>> expensive, such as this one: >>>> >>>> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=0033.1118-ND >>> How about a wall wart? You should be able to find something like that >>> for $10-$15. >> The only way to get one in would be to snip the end off a two-prong >> Christmas extension code, solder it in and strap the whole kludge down >> with cable ties. Any fire marshall would blow a gasket ;-) >> >> Plus I think wall warts don't like to bake in there. > > What exactly is it you're trying to produce? You've given several > different conflicting scenarios here. Is the user supposed to be > responsible for selecting the voltage? Does it get set at the factory? > What code are you trying to satisfy? > > Please, Joerg, tell us the "big picture" here. > Ok, big picture follows: Unit in fields, outdoors, think farm. The sun is pelting it brutally all day long and the electric stuff sits inside an enclosure, no vents big enough to write home about. No choice, it has to be that way and it works fine in a 120V version. Client wants users to be able to ideally just plug it into 120 or 240, and not worry about a thing. That ain't going to fly because SMPS modules seem to not be that great. Maybe cheap electrolytics, I don't know, but mfgs don't want to endorse >60C and it sure does get hotter than that in there. Just by the sun. So, the next best avenue would be a configurable 120/240 transformer because then we can have our own (better) switcher behind that. Unfortunately the cheap voltage selectors have become pariahs. Configuring at the factory would be ok but it has to be simple, like flicking a hidden switch or reversing an insert. But it (meaning also that switching element) must be code-compliant, in this case UL as well as VDE (CE) plus later some others, maybe Japan. Up to now it was only UL. Cost is critical. Adding a buck in total is ok, adding five bucks is not. > BTW, how do you pronounce "Joerg?" :-) > It's o-umlaut, pronounced just like Archie Bunker and many New Yorkers say "poifect" or "point". -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |