Stuart Stevenson wrote: > Gentlemen, > Jon, I don't know the level of demand for a resolver board. Would > this be a ppmc card or a separate module? I would like to have the > option in the ppmc set. If the price isn't too high I would buy five > to start. I think it makes more sense to just make a resolver to quadrature board, maybe with a DC tach emulator, too. It could still be used with the PPMC, of course. > There are still quite a few machines in service that have resolvers. > All the early Fadals have resolvers. I am not sure when they went > to pulse encoders. Both of ours have resolvers. Our newest one was > purchased in 1998. > The older Cincinatti 5 axis machines have resolvers. > I am sure as time passes the resolver demand will continue to > dwindle unless there is some overriding advantage to using resolvers > and the use is facilitated. In what application would a resolver be > the preferred choice? Why? > I have heard price is the reason people have switched to pulse > encoders. Unless alzheimer's has prevailed I remember the price of > pulse encoders is around US $150.00/$200.00. and the price of > resolvers for our Fadals is US $150.00/$200.00. Doesn't seem to be > much difference. Some of this is historical nonsense. The original optical encoders used light BULBS, and when the bulb went out, you could have a servo runaway. This gave encoders a bad name. Also, some of the early LED encoders suffered from degrading of the LED, and would eventually become unreliable. They also need good seals to protect the optics from contamination.
Resolvers can run fine when filled with water or oil, and there are no active devices in them to wear out. > Maybe the reason everyone uses digital is there is no good/cheap > way to get the analog signal into the current controls? Yes, although the latest AD chip really brings the price down. > This is definitely beyond my expertise but my perception of the > comparison between digital and analog is something like this. > With digital, the signals do not deteriorate until they just don't > work anymore. There is no adjustment necessary (or even possible). > With analog, as the individual components deteriorate the signals > need to be adjusted. Sometimes, this gets to be quite frequent and/or > involved. Yes, that is about right, although the AD chip, once set up for the right voltage and frequency, should not need any adjustment. > Therefore, the initial cost be equal, the maintenance and repair > of digital is cheaper and easier than analog. In the old days, with boards covered with dozens of trimpots, that was absolutely true. > What about pressure/temperature transducers? Would a resolver > board also be able to connect to these and allow the use of their > feedback? Maybe with another pin selection? Possibly. They often use either strain gauge or LVDT, which is somewhat related to a resolver. But, I think AD makes chips more specific for that application. A resolver-digital converter is expecting a sine/cos relationship, where those sensors produce a linear relationship between signals and position. Jon ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
