Jim Brain wrote: > On 9/13/2013 2:57 PM, Gerrit Heitsch wrote: > >> On 09/13/2013 09:15 PM, email@example.com wrote: >> >>> >>> On 2013-09-13, at 05:33, Jim Brain wrote: >>> >>>> Does anyone have ideas (or could point to a person or company) that >>>> might have a way to safely synthesize an isolated 9VAC for the >>>> machines from 5VDC? >>> >>> >>> Yes, that's one of the things, I'd like to see solved for good as >>> well. I was approaching it from different angles. Even "invented" PWM >>> based sine-wave generation once before sleep ;-) The problem always >>> was that in the end one needs a transformer, which is what I always >>> wanted to avoid in the first place.. >> >> >> You can't. There is no way around a transformer in this case. > > > I'm not opposed to a transformer. I have, I think, the other piece > > o uC DSS implementation (2 of them, one is a R2R implementation and 1 is > a PWM implementation), coupled with a power transistor and a RC filter > to smooth out the waveform. > > Now, if I could just find a 1:2 transformer that would handle 9VAC (9W?) > and work at 50 and 60 Hz, I'd be golden. > > But, I know *NOTHING* about inductors and transformers. I faintly > remember taking a part of a course on them in college, but nothing stuck. > > So, Bil et al, help would be appreciated. I looked at Coilcraft, and > saw some step down and forward mode transformers, but I need the > reverse, I think. > > Jim > > > Message was sent through the cbm-hackers mailing list > Magnetics are traditionally black magic, but transformers aren' all that hard. I assume you're talking 5VDC so you want a transformer that's more like 2.6 : 1 (9VAC is 12.73 peak) Assuming you're dead set against just using a 9VAC wallwart or something next to your 5VDC, I think I'd try 5VDC to ~ +-13VDC then synthesize the 9VAC from that. The cheap inverters use a wave form something like this. _ _ _ _| |_ _| |_ _| |_ | |_| |_| Typically (I think) with the area under the curve aproximating a sine wave and the peak close to the sine wave peak. If you were going to wind your own transformer you could give it more steps. If you were using a computer supply with +-12 and +-5 VDC you could try synthesizing it from that (maybe filtering) then running it thru a 1:1 isolation transformer. It would depend on how much power you want, PC supplies usually aren't rated for much current on the negative supplies. Message was sent through the cbm-hackers mailing listReceived on 2013-09-14 02:00:05
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