Building a transformer
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From: meow2222 on 13 Aug 2006 18:49 Phil Allison wrote: > <meow2222(a)care2.com> wrote in message > news:1155474226.768278.253900(a)75g2000cwc.googlegroups.com... > > ** Groper FROM HELL alert thank you for at least warning me. > > Need to backtrack on the maths a bit first. To get 50v dc regulated you > > need 50v dc +5v for regulator drop + 3v for rectifier drop + say 15% to > > allow for mains sag. Thats 66.7v dc. > > > > Now to get 66.7v dc peak you need 66.7 / 1.414 = 47v ac. > > > > To get +-50v dc you need the same transformer, no reason to have 2 > > windings at all. So you just need one 50v winding. > > > ** So a two diode voltage doubler ?? dont be dense. NT
From: Phil Allison on 13 Aug 2006 22:27 <meow2222(a)care2.com> wrote in message news:1155509358.338411.288670(a)74g2000cwt.googlegroups.com... ** MASSIVE GOOGLE FUCKWIT ALERT ~!!~ >> > To get +-50v dc you need the same transformer, no reason to have 2 >> > windings at all. So you just need one 50v winding. >> >> >> ** So a two diode voltage doubler ?? > > dont be dense. ** Uranium is translucent compared to this asinine POS. ......... Phil
From:
John Woodgate on 14 Aug 2006 01:50 In message <1155474226.768278.253900(a)75g2000cwc.googlegroups.com>, dated Sun, 13 Aug 2006, meow2222(a)care2.com writes >Need to backtrack on the maths a bit first. To get 50v dc regulated you >need 50v dc +5v for regulator drop + 3v for rectifier drop + say 15% to >allow for mains sag. Thats 66.7v dc. You've allowed for all those and forgotten transformer impedance (usually expressed as 'regulation', when it's the opposite). For this sort of transformer, you can expect the open circuit voltage to be 5% higher than the full-load voltage. > >Now to get 66.7v dc peak you need 66.7 / 1.414 = 47v ac. Again, that's the voltage you would get with no output current. Calculating what you get with a given output current is difficult, but you can get an approximate value by assuming that the diodes conduct for (these days, with BIG filter caps) a quarter of a cycle. It's difficult to explain the calculation without a diagram and I don't have time to do it at the moment. > >To get +-50v dc you need the same transformer, no reason to have 2 >windings at all. So you just need one 50v winding. > > >Now, current. If you play it within all specs you could use 5A x 1.6 = >8A transformer. But I built supplies for years when younger without >using that 1.6 factor and never had any problems from the bridges or >tfs, and since this is for personal hobby use I'd be tempted to do >that. Or if you need something portable you could even go smaller and >add fan cooling. If you were 'younger' 30 or more years ago, and operated your transformers outside of an enclosure, you got away with it. Modern transformers, with those big filter caps (resulting in higher r.m.s. diode current), mean higher temperature rises, and you won't get away with it now. Diodes now have lower losses, so they generally don't overheat. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk 2006 is YMMVI- Your mileage may vary immensely. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
From: joseph2k on 14 Aug 2006 06:06 RST Engineering (jw) wrote: > What primitive semiconductors did you use in the output stage, or was it a > toob device? Did we have 2N3055s in '75? I don't memember. > > Jim > > > >> I couldn't get him really interested until I sweetened the pie by >> offering to help him build a 400W guitar amplifier IF he got an "A" in >> Algebra. >> >> He did get the "A". >> >> We built this beautiful thing (in 1975) that was so heavy that it took >> two people to carry it, and I had to use fans on the heat-sinks ;-) >> >> Put out 400W RMS into 4 x 16 ohm speakers in parallel. Kinda late but i was playing around with 2n3055's in the late 1960's. Also 2n4400's i think. -- JosephKK Gegen dummheit kampfen die Gotter Selbst, vergebens. --Schiller
From: joseph2k on 14 Aug 2006 06:11
Jim Thompson wrote: > On Tue, 08 Aug 2006 14:48:15 -0700, Tim Wescott <tim(a)seemywebsite.com> > wrote: > >>Jim Thompson wrote: >>> On Tue, 08 Aug 2006 21:19:21 GMT, "ian field" <dai.ode(a)ntlworld.com> >>> wrote: >>> >>> >>>>"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote in >>>>message news:99uhd21d83biuj4122hfrv1p47k4gip41h(a)4ax.com... >>>> >>>>>On Tue, 8 Aug 2006 13:44:27 -0700, "RST Engineering \(jw\)" >>>>><jim(a)rstengineering.com> wrote: >>>>> >>>>> >>>>>>What primitive semiconductors did you use in the output stage, or was >>>>>>it a >>>>>>toob device? Did we have 2N3055s in '75? I don't memember. >>>>>> >>>>>>Jim >>>>>> >>>>> >>>>>[snip] >>>>> >>>>>I'm trying to remember what semiconductors I used. But, IIRC, >>>>>2N3055's *were* available around that time. >>>>> >>>>> ...Jim Thompson > >>>> >>>>Was it Ge or Si ? >>>> >>> >>> >>> It was Silicon. I didn't use any Germanium power devices since I >>> boosted my car radio back when I was a junior in high school. >>> >>> ...Jim Thompson >> >>Correction: it _is_ silicon. >>http://www.onsemi.com/pub/Collateral/2N3055-D.PDF. >> >>Digi-Key has them for $2.10 a pop, in the TO-3 case, no less. > > I said it was silicon. The Ge device I used in HS was a Delco > doorknob power device. I did 10W class-A ;-) > > ...Jim Thompson OK. You have used a "doorknob" power device. What the heck did it look like? Where can i find outline drawings? You are about the third person i have heard admit of their existence. -- JosephKK Gegen dummheit kampfen die Gotter Selbst, vergebens. --Schiller |