115/230V voltage switch key for transformer?
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From: Fred Bartoli on 25 Nov 2009 15:48 Joerg a �crit : > 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. > Have a dual 120V primaries xfrmer with a relay switched series/parallel connection. The relay rest position is connecting the xfrmer in 240V mode, then you have all the time you need to decide what to do with the relay. Cost: one relay and 10c parts. But I'm confident you'll find something that won't fit ;-) -- Thanks, Fred.
From: Joerg on 25 Nov 2009 15:54 Fred Bartoli wrote: > Joerg a �crit : >> 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. >> > > Have a dual 120V primaries xfrmer with a relay switched series/parallel > connection. > The relay rest position is connecting the xfrmer in 240V mode, then you > have all the time you need to decide what to do with the relay. > Cost: one relay and 10c parts. > > But I'm confident you'll find something that won't fit ;-) > Yeah, two things :-( One, a primary side relay adds more than those 10 cents. The other is that a brown-out situation would cause the relay to partially let go ... bzzz ... phssss ... *PHOOMP* Of course I could make a brown-out detector and all that. But things would need to go fast because the transformer is without power during the switch-over. Did you decide which theremin to build with your daughter? -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Joerg on 25 Nov 2009 15:56 Rich Grise wrote: > 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. > Yes, sometimes, but as usual, integrated into the IEC connector. Can't use that, no space. > 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? > Well, there will be sluggish brown-outs and the like. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Fred Bartoli on 25 Nov 2009 16:11 Joerg a �crit : > Fred Bartoli wrote: >> Joerg a �crit : >>> 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. >>> >> >> Have a dual 120V primaries xfrmer with a relay switched >> series/parallel connection. >> The relay rest position is connecting the xfrmer in 240V mode, then >> you have all the time you need to decide what to do with the relay. >> Cost: one relay and 10c parts. >> >> But I'm confident you'll find something that won't fit ;-) >> > > Yeah, two things :-( > > One, a primary side relay adds more than those 10 cents. You said 1 buck is OK, not five. I said one relay and 10c parts. I guess that would not make for 5 bucks... The other is > that a brown-out situation would cause the relay to partially let go ... > bzzz ... phssss ... *PHOOMP* > > Of course I could make a brown-out detector and all that. But things > would need to go fast because the transformer is without power during > the switch-over. > But don't you have a bulk cap somewhere? Just keep the relay in the same state until the bulk cap voltage is over. And if you use a low voltage coil WRT to the nominal bulk cap rail, then you have plenty brownout time before the relay decides to switch back. Oh, and it'll never switch on 240 mains, so in not 3rd world countries we won't experience any failure at all. > Did you decide which theremin to build with your daughter? > Not yet, but I got some bit of interesting info I didn't think about, like the one (it's all about ergonomic) that use some "linearizing trick" to get a usable hand stroke. But I don't like the way they do it (1000s turns coil). Also the one you pointed me too was already preassembled. Just fit it in the box and voil�. That's not what I was after. But now I begin to feel I've the info I missed to design a good one, so I might go that path. Of course work will get in the way, but... -- Thanks, Fred.
From: Baron on 25 Nov 2009 17:02
Joerg wrote: > petrus bitbyter wrote: >> <osr(a)uakron.edu> schreef in bericht >> news:f664eb19-4b19-4565-b198-87d60393c2a8(a)j19g2000yqk.googlegroups.com... >> On Nov 24, 8:48 pm, Joerg <inva...(a)invalid.invalid> wrote: >>> Hello Folks, >>> >>> Never needed this before but now I do: What are those things called >>> that you unplug and insert 180 degrees rotated to switch the >>> primaries of a transformer between 115V operation (parallel) and >>> 230V operation (series)? Circuit board mount. >>> >>> Or better yet, does anyone know a source? Must be super cheap, as in >>> <<50c altogether in qties, as usual :-) >>> >>> Under categories such as "voltage selector" I only found fuse >>> holders with this feature in there, really expensive plus way too >>> large. I want to avoid a slide switch because someone could >>> accidentally hit it and ... *PHUT* >>> >>> -- >>> Regards, Joerg >>> >>> http://www.analogconsultants.com/ >>> >>> "gmail" domain blocked because of excessive spam. >>> Use another domain or send PM. >> >> | The classic term used in Marshall and other Audio Amps is voltage >> | selector plug. >> | >> | Somebody decided they should be removed from the electrical code. >> | Your left with the voltage selecting fuseholders. try schurter. >> | >> | Steve >> | >> >> FAIK that old method does not meet current EU safety regulations >> anymore. So that selectors became obsolete. >> >> 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. Dunno if it helps, I've seen multi pole jumpers used for voltage selection where the cap has multiple links in it. -- Best Regards: Baron. |