Norm, Stepper motors work. You can actually see it turning two real sat antennas on a 4 foot cross boom and it is not as big as a bike. No obscure parts used.
http://www.tomdoyle.org/satellite/SatTrackerRotor.html W9KE Tom Doyle On Fri, Mar 1, 2013 at 1:17 AM, Lizeth Norman <normanliz...@gmail.com>wrote: > Gus and all: > Had a bad experience with a stepper motor based 3 axis mill project. > That thing had a mind of it's own. Definitely needed the big red kill > switch every once in a while. > > The choice of a position sensor is as much as what you can get locally > that meets the need as what will work. > > Three turn pots are necessary unless we want to limit rotation to 360 > degrees. Easy enough to in satpc32. > Also, not all pots rotate 360. Some only 320, some less. The more > expensive pots have much greater possible feature set. The Arduino > does not care what we use.. > What sort of position encoders are available in your local surplus > store? How about available as salvage from other gear?? > > Am going to Peru towards the end of April. What's available here and > what's available there are two different things. > Last time I visited, a few OT's and I had a conversation regarding > exactly what we have been discussing, namely an inexpensive full > featured satellite station using mostly homebrew for super cheep. > > Norm > > > On Fri, Mar 1, 2013 at 12:29 AM, Gus <8p...@anjo.com> wrote: > > On 02/28/2013 11:24 PM, Lizeth Norman wrote: > >> > >> A stepper still needs some sort of position feedback.. > >> > >> > > Not really. > > > > Steppers rotate a predictable amount with each step. To calibrate, the > > software only needs to count steps from one limit switch to the other. > > Then, by keeping track of step count (+/-), it will always know exactly > how > > far round the turn it is. It can store last position in NV RAM or > EEPROM, > > so as to avoid the need to recalibrate on every startup. > > > > Unfortunately, I can't think of a common source for surplus steppers of > > useful size. And driving them is slightly more complicated than firing a > > relay to a DC motor. > > > > > > OK, why do we have to use A multi-turn pot? Why not just an ordinary > linear > > pot? > > > > > > -- 73, de Gus 8P6SM > > Barbados, the easternmost isle. > > _______________________________________________ > > Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. > > Not an AMSAT-NA member? Join now to support the amateur satellite > program! > > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb > _______________________________________________ > Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. > Not an AMSAT-NA member? Join now to support the amateur satellite program! > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb > -- Sent from my computer. tom ... _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
