Building a transformer
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From: John Fields on 14 Aug 2006 09:02 On 13 Aug 2006 06:03:46 -0700, meow2222(a)care2.com wrote: >Mark Fortune wrote: > >> Greetings to the collective. >> >> For my next project I want to build a bench power supply and do away >> with this old switch mode AT computer PSU that i'm currently using. >> >> The design I have in mind will be pretty beefy, giving a wide range of >> fixed and variable output voltages (i'm thinking from -50v up to +50) >> and deliver up to 5amps of current. if my estimates are right i'll need >> a 600va+ (100v * 5a + overhead) transformer to do the job well. Now i've >> had a look at some transformers in this range, and they're a little out >> of my price range. so now i'm considering building my own. >> >> The specifications I need are as follows: >> >> primary: 0-230v @ 50Hz >> Secondary: 60v-0-60v >> secondary output current max: 5A > >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. > > >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. > >So you need 50v 5A = 250w transformer. > >Toroidals are smaller, lighter, and more money. Microwave transformers >should be avoided, they just need too many mods to be worth playing >with. > >I'd be asking myself if I really needed +-50v at 5A, and would be >answering no. I once had a massive all singing psu and almost never >used it. A small portable bench supply is a lot easier to use than a >meatlump. For those occasional jobs that need more power I'd use >something much more basic. > >These days I'd buy one, or maybe look at modding a pair of pc psus if >for some reaosn thats not an option. > > >NT -- John Fields Professional Circuit Designer
From: ian field on 14 Aug 2006 11:21 "joseph2k" <quiettechblue(a)yahoo.com> wrote in message news:d%XDg.8137$kO3.4237(a)newssvr12.news.prodigy.com... > 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 There were "doorknob" tubes as well - which actually looked like glass doorknobs.
From: Jim Thompson on 14 Aug 2006 11:48 On Mon, 14 Aug 2006 10:11:21 GMT, joseph2k <quiettechblue(a)yahoo.com> wrote: >Jim Thompson wrote: > [snip] >> >> 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. I probably have an appropriate data book around here somewhere. I'll look for it. ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Jim Thompson on 14 Aug 2006 12:28 On Mon, 14 Aug 2006 08:48:42 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: >On Mon, 14 Aug 2006 10:11:21 GMT, joseph2k <quiettechblue(a)yahoo.com> >wrote: > >>Jim Thompson wrote: >> >[snip] >>> >>> 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. > >I probably have an appropriate data book around here somewhere. I'll >look for it. > > ...Jim Thompson See.... http://analog-innovations.com/SED/2N1358.jpg ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Michael A. Terrell on 14 Aug 2006 13:49
joseph2k wrote: > > 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. The DS501/2N441 was a "Doorknob", AKA "JEDEC TO-36" package. I can put some pictures on alt.binaries.schematics.electronic if you want to see a real part. -- Service to my country? Been there, Done that, and I've got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida |