I took a look around at a few semiconductor manufacturers, and found an app note from Freescale (Motorola), on their MC3PHAC AC motor drive chip. It does use an external timebase of 4 MHz, but they only used a resonator, and this could be made way more precise. Though this is a 3 phase controller IC, they do make drives for smaller single phase motors, but I'm not sure who makes the controller IC's, nor do I know about any external time bases for them.
It could be as simple as buying a surplus, single phase, AC motor drive, and setting it up for the correct speed, and adding a good timebase in place of a resonator. I have seen these types of drives sell for pennies on the dollar on ebay. It might be worth taking a look at. Best, Will *********** REPLY SEPARATOR *********** On 6/25/2011 at 1:38 PM J. Forster wrote: >> John, >> >> I forgot to add, that an H bridge could work for a clock motor, since >> those are used to drive ac motors in industry every day. > >Yes, of course. > >> You would have a sqauare >> wave though, unless it was modified. If I recall, that's the way a lot of >> the AC drives work today, using four sets of switching semiconductors, >> unless the motor is small enough to be ran off a power chip. In this >case, I wonder how an AC drive would act if it ran a clock motor? > >The static inverters should not have issues with an induction motor. > >> Set it at 60 Hz, and be done with it? > >Yes, but you have to get to the H bridge timing logic to do that. That's >why you need the prints. > >-John > >=================== >> >> Best, >> >> Will >> >> *********** REPLY SEPARATOR *********** >> >> On 6/25/2011 at 12:55 PM J. Forster wrote: >> >>>Certainly, the inverters can run that low, but if so they sing a lot. >>> >>>Best, >>> >>>-John >>> >>>================= >>> >>>> John, >>>> >>>> I didn't mean to say you said all that, just that the new inverters are >>>> cheap. I wrote that I thought some ran at around 1 kHZ, as I had an old >>>> one >>>> that did, and used a toroidal transformer in it. The new ones, as far >>>> as >> I >>>> am aware, are similar to the new-style switching power supplies, like >> the >>>> ones Maxim and a few others show in their app notes. >>>> >>>> Best, >>>> >>>> Will >>>> >>>> *********** REPLY SEPARATOR *********** >>>> >>>> On 6/25/2011 at 12:37 PM J. Forster wrote: >>>> >>>>>> Chris, >>>>> >>>>>No I didn't say the output was 1000 Hz. No way. >>>>> >>>>>What I said (a bit amplified) was that the cheapie inverters use a high >>>>>frequency, think 50 KHzish, DC-DC converter to make about 170 VDC, then >>>>>use that to feed an "H" bridge, driven with either a square wave or a >>>>>modified square wave, to make the output. You snmply need to vary that >>>>>drive frequency to get 50, or 60, or any frequency you want. >>>>> >>>>>There is no output transformer. In fact, that is the cleverness of the >>>>>design... no big, heavy, expensive magnetics. >>>>> >>>>>-John >>>>> >>>>>=================== >>>>> >>>>>> As John mentioned earlier, the el-cheapo inverters are pretty much >>>>>> junk, and run as high as 1 kHz, if I recall. They were made to run >>>>>> small >>>>>> TV's, etc, that don't require a fixed line frequency, since they all >>>> have >>>>>> hot chassis now that don't use isolation transformers. >>>>>> >>>>>> Best, >>>>>> >>>>>> Will >>>>>> >>>>>> *********** REPLY SEPARATOR *********** >>>>>> >>>>>> On 6/25/2011 at 11:55 AM Chris Albertson wrote: >>>>>> >>>>>>>> The reason for using 12 Vdc, is that you can pick them up, and 24 >> Vac >>>>>>>> CT >>>>>>>> transformer, on the cheap >>>>>>> >>>>>>>That's a good point. So use two of them. One to power a high >>>>>>>current amp that produces a 12V AC signal from a high precision 60Hz >>>>>>>input. Then the other to convert the 12V to 120V. This avoids the >>>>>>>need for a high voltage DC power supply. Likely cuts the total cost >>>>>>>in half at least. So just use use 12V supply to the amp and then >>>>>>> a >>>>>>>cheap 12V transformer connected "backwards" to step up to the desired >>>>>>>voltage. >>>>>>> >>>>>>>The second advantage of this design is that you can connect a lead >>>>>>>acid gell cell battery in parallel to the 12V DC supply and if the AC >>>>>>>fails the battery will power the amp for a while. This way there is >>>>>>>no switching so the 60Hz wave remains continuously even if AC mains >>>>>>>fails. >>>>>>> >>>>>>>This is something most UPS don't do but for this application you >>>>>>> don't >>>>>>>want the 60Hz sine wave to be broken. >>>>>>> >>>>>>>As long as the load is only a few milliamps of AC this should not be >>>>>>>hard to do. >>>>>>> >>>>>>> >>>>>>>-- >>>>>>> >>>>>>>Chris Albertson >>>>>>>Redondo Beach, California >>>>> >>>>> >>>>> >>>>>__________ Information from ESET Smart Security, version of virus >>>> signature database 5851 (20110206) __________ >>>>> >>>>>The message was checked by ESET Smart Security. >>>>> >>>>>http://www.eset.com >>>> >>>> >>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>>> >>>> >>> >>> >>> >>>__________ Information from ESET Smart Security, version of virus >> signature database 5851 (20110206) __________ >>> >>>The message was checked by ESET Smart Security. >>> >>>http://www.eset.com >> >> >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> > > > >__________ Information from ESET Smart Security, version of virus signature database 5851 (20110206) __________ > >The message was checked by ESET Smart Security. > >http://www.eset.com _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
