Post by thread:DC to AC inverter

-----Original Message----- From: Eduardo R. <.....eriveraKILLspam@spam@UMEMPHIS.CAMPUS.MCI.NET> To: PICLISTKILLspamMITVMA.MIT.EDU <.....PICLISTKILLspam.....MITVMA.MIT.EDU> Date: Monday, March 22, 1999 7:23 AM Subject: DC to AC inverter > I am looking for an application to get 110V. AC using a 12V. battery. Has >anyone successfuly tried it? I've played with this application but not with any success due to lack of persistence. I was using a PIC to drive some big power mosfets, in an Hbridge arrangement around a transformer. The idea was to first drive the transformer with 60HZ square waves, then in phase II try to go to a pseudo sine wave idea. I'd like to see a successful design in this area, I might try to build it again.

Lawrence Lile wrote: > > -----Original Message----- > From: Eduardo R. <EraseMEeriveraspam_OUTTakeThisOuTUMEMPHIS.CAMPUS.MCI.NET> > To: PICLISTspam_OUTMITVMA.MIT.EDU <@spam@PICLISTKILLspamMITVMA.MIT.EDU> > Date: Monday, March 22, 1999 7:23 AM > Subject: DC to AC inverter > > > I am looking for an application to get 110V. AC using a 12V. battery. Has > >anyone successfuly tried it? > > I've played with this application but not with any success due to lack of > persistence. I was using a PIC to drive some big power mosfets, in an > Hbridge arrangement around a transformer. The idea was to first drive the > transformer with 60HZ square waves, then in phase II try to go to a pseudo > sine wave idea. > > I'd like to see a successful design in this area, I might try to build it > again. I think there is a "reference design" on an UPS on microchip site. I think that should solve your problem. And since the design contains a PIC this answer is not considered OT either :-) regards /Sten -- Sten Dahlgren ! I'd rather have 39 hp under my right arm than Enea Data AB ! one horse under my bottom ! Box 232 ! Join your nearest karting club ! 183 23 TŠby ! Sweden ! +46 8 6385000 ! KILLspamstdaKILLspamenea.se !

On Mon, 22 Mar 1999 08:37:51 -0600 Lawrence Lile <RemoveMElilelTakeThisOuTtoastmaster.com> writes: {Quote hidden}>-----Original Message----- >From: Eduardo R. <spamBeGoneeriveraspamBeGoneUMEMPHIS.CAMPUS.MCI.NET> >To: TakeThisOuTPICLISTEraseMEspam_OUTMITVMA.MIT.EDU <RemoveMEPICLISTTakeThisOuTMITVMA.MIT.EDU> >Date: Monday, March 22, 1999 7:23 AM >Subject: DC to AC inverter > > >> I am looking for an application to get 110V. AC using a 12V. >battery. Has >>anyone successfuly tried it? > > >I've played with this application but not with any success due to lack >of >persistence. I was using a PIC to drive some big power mosfets, in an >Hbridge arrangement around a transformer. The idea was to first drive >the >transformer with 60HZ square waves, then in phase II try to go to a >pseudo >sine wave idea. > > >I'd like to see a successful design in this area, I might try to build >it >again. > Not QUITE the same thing, but we did an inverter for use at solar powered telemetery sites for oil and gas pipelines. The 16c61 based device would watch an RS232 line and the phone line for any activity (like phone line loop current or ringing, or the telemetry trying to send something). The 16c61 would then generate 60 Hz gate drive to a pair of FETs that drove a transformer. The secondary of the transformer was 12VAC square wave that then powered an external modem. After inactivity for a user specified time (using a thumbwheel switch), the AC would be shut down. It seems to me that the most difficult part of such a project is in the transformer design. I just gave my requirements to a local transformer manufacturer and they came back with a working prototype. We then just ordered more. I used a center tapped transformer instead of an H bridge with 4 FETs. This seems lower cost. Going to pseudo-sine using PWM would be interesting, and more complex! You'd need a low pass or band pass filter (probably) after the transformer. Design of the filter would be interesting, since you don't really know what it would be terminated in to. I recall from my daze working on broadcast transmitters that we used to use class C amplifiers for the highest efficiency. The tube would conduct for only a small portion of the cycle, but there was still a sine wave on the plate of the tube. This increased the tube dissipation since the "rounding" of the sine wave forced there to be some voltage on the plate when the tube was conducting. One manufacturer added a third harmonic resonator allowing the plate voltage to be more square (since it now included the fundamental and the third harmonic), vastly increasing the efficiency over the 70% typicla for a class C amplifier. I would imagine a similar technique could be used in an inverter to get higher efficiency. Finally, a word about cost... Inverters and UPS's are CHEAP! I certainly wouldn't want to try to compete in that market! Harold Harold Hallikainen haroldEraseME.....hallikainen.com Hallikainen & Friends, Inc. See the FCC Rules at http://hallikainen.com/FccRules and comments filed in LPFM proceeding at http://hallikainen.com/lpfm ___________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com/getjuno.html or call Juno at (800) 654-JUNO [654-5866]

-----Original Message----- From: Eduardo R. <EraseMEeriveraumemphis.campus.mci.net> To: Lawrence Lile <RemoveMElilelEraseMEEraseMEtoastmaster.com> Date: Monday, March 22, 1999 8:13 PM Subject: Re: DC to AC inverter > What kind of difficulties did you experienced ? My biggest difficulty was timing the signals to the mosfets. I was using a homebrewed mosfet driver built up out of discretes. If the signals were not timed right, both arms of the H-bridge would be on at the same time tresulting in a dead short across my power source. As this was a 12V car battery, it made quite a mess. Later I learned of mosfet driver chips that can prevent this problem. Another post recommended a center tapped transformer which might eliminate the need for the H bridge and change the cost and complexity. I never got back into that project as it was just a hobby effort. Lots of fun though, and one of my earliest efforts at using a PIC for more than blinking lights.