Another long delay, but this time the telescope project has been totally remade.
All the framework has been machined out of Aluminum sheets making the unit much more rigid without being too heavy, plus re-sized to allow for a larger telescope in the future (the current 4.5″ mirror isn’t all that exciting… ). I’ve also used secondary gearing so I get more torque out of the motors as well as better accuracy – I now get 0.0018 degrees per step.
Electronics are based around the NXP LPCeXpresso dev board using an lpc1769 ARM processor. The NXP chip controls 3 separate motor circuits gated for 12V drivers ( Azimuth, Altitude and Focus) all timed off separate timers so each can be individually speed regulated. Communication with the PC is by a Bluetooth serial module and the board also drives a 132×132 pixel color LCDmodule to show tracking details. This chip runs at 120MHz and has plenty of speed to keep tracking and control as smooth as possible.
I’ve mostly programmed the NXP to emulate the SynScan AltAz GOTO mount commands as well as a few of my own custom for other work. This command set allows easy control via Stellarium software for field work.
This video shows the mount going from flat North to M48 then to the Moon via PC, then I click the Home button on the hand controller at the end.
This video is the same but from the software viewpoint.
Just need to weatherproof the electronics inside a box and add a stable mount. (then get a real telescope for it… )
Until next time!
How do you like the Expresso IDE? I’m looking at moving an Arduino project over to the LPC1769 and wanted some of your feedback.. Looks like a monster of a chip..
I love the LPC chips, they have a surprising amount of power and speed. As for the IDE that took a few trials to sort, I eventually discovered that by compiling as a release instead of debug then it gave my board a LOT more speed and a MUCH smaller memory usage. I very quickly filled the free licence limits running under debug compile and get very upset with it but now I’m running release builds it works very sweet. I think my current compile is about 28kB
I have since bought a few lpc1954’s for some smaller projects and am planning to get a few LPC1768’s as well.
Will you be releasing the source code and build? What do you use for sensors? I love the movement it is so smooth.
I have a project that I’d like to assemble this summer that will track satellites (but could also be pointed at celestial objects). I can figure out how to drive the stepper motors, struggle through MCU programming, but am clueless about how standard Sky Chart sends “GoTo” signals and the corresponding protocol. How is this done? Also, would the PC continuously output coordinates of the satellite, and my PIC/Arduiino/ARM chip translate that into stepper motor movements, or would it be better to send the microcontroller the trajectory, whereby it would translate the data into an acquisition position followed by a constant rate slew across the sky? I appreciate your thoughts, an e-mail correspondence might be more appropriate.
Sounds like a good project, had similar in mind on mine when I started for tracking things like the ISS.
Signals from software is the real challenge, when I started I found it very difficult to find much specs on the various protocols used, I ended up with Synscan GOTO protocols as it was the only spec sheet I could find that was simple enough to implement to my code, took me ages to find it, then I had to snoop on the output from Stellarium to see what commands IT was using to drive the scope.
Google for “Synscan GOTO Protocol” and you should get a couple of pdf links. This one http://ca.skywatcher.com/upfiles/en_download_caty01335568752.pdf for eg, then look at appendix B for the protocol.
The main issue I had was that Stellarium would point the scope at an object but not actively track it, it instead relied on the fact that most goto mounts would naturally track on sidereal movement. As most RA mounts do, but since I had Alt/Az tracking I had to program in sidereal tracking with my own code.
I have not looked at Satellite tracking for a long time (>10 years) so I have no idea what protocols software would use or what formulas there are for calculating movements. Since their movements are based on orbits instead of just earth rotation like stars. Although planet tracking is on my TODO list.
A quick Google search I find this may be a place to start: http://www.amsat.org/amsat/ftpsoft.html#win-rot
Look for source code I guess and see what they do and how, maybe search for the actual formulas used for tracking from the satellite lists that can be downloaded and go from there.
Myself I’d do the calculations on the chip for tracking in real time. Tho you’d need a fast chip, I’d doubt a PIC would do it, my code on the LPC arm chip gets about 20 updates/sec calculating sidereal in real time. From there you could send the satellite’s orbit data you wanted to track via serial to the chip and let the chip track from there. Unless you find software that would send real-time alt/az data to the chip then any chip would do. I remember in DOS days a program called Orbit that would do that, but thats like 15+ years ago…
Hope some of this helps point you in the right direction, sorry there’s no direct answer, but that’s programming in my experience 🙂