I have used a 9 DOF sensor on the tail of the PVC cradle that sometimes holds my Elk. It provides the feedback to an ESP processor that sends commands to the az and el servos. There’s also a GPS board that tells the ESP where the antenna is located. TLEs are wifi’d to the tracking code on the ESP. The design of this autonomous, portable satellite tracker was developed a few years ago by WB0OEW and published in QEX. The DOF sensor includes an accelerometer and magnetometer. My comment is that these can be pretty cranky, although there may be better boards now available. Cranky in that 1) the sensor I have requires a frequent calibration ritual and 2) RF sometimes drives it crazy despite liberal use of ferrites and wrapping the sensor in foil. I appreciate the references in this thread because I want to build a new tracker that uses just the servos and the servo control board from the old one. I’d like to interface the servo controller over a USB cable to a laptop running SatPC32. Wish I could get this figured out before FD this year so I can stay sealed inside the tent at night while the tracker does its thing outside. The bugs were horrible last year. Ray KN2K
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On Tuesday, February 8, 2022, 6:36 PM, Burns Fisher wb1fj-bb@fisher.cc wrote:
BTW, check the latest QST for another piece of the puzzle. This guy gets the azimuth reading from the single-chip magnetometer. Someday I thought it would be fun to use a magnetometer and an accelerometer (to measure the acceleration due to gravity) to get both Az and El without pots.
On Tue, Feb 8, 2022 at 2:31 PM Martin Cooper via AMSAT-BB amsat-bb@amsat.org wrote:
Hi Joe, Ha ha! You're right there. I think my total came to about $50, including a case, which was the most expensive item. A lot more than the digital pot solution, but not too bad for a complete rotator controller. Martin.KD6YAM On Tue, Feb 8, 2022 at 10:23 AM Joseph B. Fitzgerald jfitzgerald@alum.wpi.edu wrote:
Martin,
Yes a SAEBRTrack type approach is more general purpose than the AA2TX digital pot solution, it can be used with pretty much any pair of rotors. Tony was never really happy unless you could fill your entire bill of materials for less than $5 - and 4 relays plus the microcontroller and drive electronics blows that budget!
I checked eBay, and apparently missed my opportunity in December for two new old stock Orbit 360's. I did find an RCA rotor only deal that I could not pass up though ... it arrives this weekend!
de KM1P Joe
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