Good points, Bob. At 400 Hz and low power, I'd think a decent LC low-pass filter would be feasible for cleaning up any trash on the inverter output. LC to minimize the series losses and provide a bit of peaking at 400 Hz.
Tom Holmes, N8ZM Tipp City, OH EM79 > -----Original Message----- > From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On > Behalf Of Bob Camp > Sent: Wednesday, March 27, 2013 6:21 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] OT - DC-10 gyros > > Hi > > The first question is "how much 400 Hz power do I need?". Without knowing if it's > tens of amps (no, it's not.) or a tenth of an amp, it's a bit though to decide how > much to spend on the solution. > > Eight ohms at 28 volts would be just a bit under 4 amps. It's also right at 100 > watts. I'd be very surprised it you need anywhere near that much current. You > probably want a pure sine wave to keep everything happy. A lot of the simple > inverters are "sort of" sine waves. I think I'd vote for something like an cheap > audio amp driven by a nice clean / stable 400 Hz tone. > > Bob > > On Mar 27, 2013, at 4:40 PM, Bill Ezell <w...@quackers.net> wrote: > > > Well, I can come up with something topical, read on. :) > > > > I saw a 'Bendix yaw-rate gyro' on FleaBay recently for $14.50. Of course, I had > to buy it. > > > > What I got was the yaw-rate gyro package from a Northwest Airlines DC-10 that > was stripped for parts around 2000. The gyro included the pull tag with tail > number, the license number of the A&P mechanic that pulled it, and some other > cool stuff. > > > > What it turned out to really be is two gyros with two sets of electronics in one > box about 6" x 2" x 5" box, all vintage '80s or so. Even better, it's a strapdown > system. The actual gyro wheel is about the size of your thumbnail. I've just started > tracing things out, and I've gotten the gyros to spin up. I really love mechanical > gyros for some reason, too bad there's not a gyro-nuts group. I'm going to have > great fun getting the package traced out and running. > > > > So, to be a bit more topical, the package of course needs 28V 400Hz for the > gyros, 28VDC for something, and +/-15V for most of the electronics. > > > > Question - anyone figured out some clever solution for the 400Hz power? I > faked it with a signal generator and power amp, but that's a bit bulky. I'm thinking > I'll use one of the class-D amp ICs and a simple op-amp phase-shift sine > generator. > > > > Topical in a more abstract way, strapdown systems really are very interesting. > They require precise integration of the rate output over time to derive velocity and > position, and really weren't practical until the 70's when small enough computers > existed to do the requisite calculations. (I worked on the nav system for the > Trident missile back in my Draper Labs days). > > > > -- > > Bill Ezell > > ---- > > They said 'Windows or better' > > so I used Linux. > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.