Retired airline pilot.Enjoy building grinding and polishing mirrors and showing the wonders of the universe to others at star parties
"My advice is free and worth every penny!"
AP 130EDF-GT & AP Mach1
C14-XLT & AP 900GTO
Quote:Thanks for the tips and the inspiration!A heftier battery would indeed be a good start. A switching regulator would also be a smart decision. I was using the 7805 mostly because I had it laying around and I needed 5V for the arduino. However, the stepper motor draws a decent amount of current and the regulator would get incredibly hot. I'll add a switching type regulator to my next digikey order and explore some different battery options. I'd like to get the current through the stepper down to around 200 mA as well.Chris, that's a nice looking barndoor tracker right there. Small, simple, clean. I'll try using vice grips on the hinge to see if I can get rid of some of the play.I'm really hoping to get some quality wide-field (up to 105mm) imaging done with this tracker.
Quote:I've looked at the ZX24r and I don't really see how it is simpler for the beginner than an Arduino..sure it's Basic but the weird mangled C++ dialect used by Arduino is pretty simple, too.. and between a China Arduino Nano fur under $10 and a "special package" containing a ULN2003 chip and stepper motor with 1/64 gear reduction.. you're all set.
Quote:I think the Arduino is a good choice if people are interested in programming microcontrollers, but are intimidated by the learning curve associated with both the electronics and programming aspects. As they learn and write more complicated programs, they can delve further and branch out. The arduino also serves as a development platform so that people can test ideas on the fly and see what would work and what wouldn't work. I don't have to move the chip from my programmer to the circuit each time I make a change. In my final design, I'll probably end up with a PIC or ATmega driven circuit and move my Arduino to other projects under development. On a stepper related note: Currently I'm half-stepping my motor, but would be interested in microstepping for smoother function. Can microstepping be easily implemented in software without any additional ICs?
Quote:There really is no need to go looking through junky printers when you can get this for $3.20http://www.ebay.com/bhp/stepper-motor-driver-board-uln2003(and that's including shipping)Actually the nice thing about an Arduino is if you buy an Uno (with the DIP28 packaged Atmega328, not the SMD package) you can pull out the Atmega328, wire it up to a super-minimal circuit (2 small caps, 1 bypass cap, and a crystal) and it will still work. http://www.instructables.com/id/Standalone-Arduino-ATMega-chip-on-breadboard/"Arduino" is nothing more than a tiny bootloader for the AVR, and a nice IDE that hides the ugliness of AVRdude and the cross-compiler.Here's another wrinkle.. the good folks at Digilent have come up with a new board, the DP32. It is not physically compatible with Arduino, but it is software-compatible and uses the MPIDE (Arduino-compatible) IDE from Digilent.The nice thing? the DP32 uses a PICMX that is also a DIP28 and can also be put in a minimal circuit like the Atmega328. The difference? 50 MHz, 512K of flash, and 32K of RAM - enough to implement a full-blown telescope controller with GoTo. If you want to go there..
Quote:Chris, the stepper motor in that link has a 1/64 gear head and is unipolar with 48 ppr. I have like 10 of them.So $3.20 with shipping for both the gear head stepper and the ULN2003 board can't be beat.
Quote:one huge advantage of using a stepper motor and micro-controller, is that you can get away without a bent shaft.with a straight shaft the speed has to be varied as you go along the shaft (this is what the Astrotrac does). So in your shoes, I'd use an Arduino, an A4988 Pololu stepper motor controller, the AccelStepper library, and one of those steppers (you could micro-step them to smooth them out, but frankly at 400 steps/rev it will not be an issue).You can also do guiding and periodic error correction with the Arduino...
Quote:Quote:one huge advantage of using a stepper motor and micro-controller, is that you can get away without a bent shaft.with a straight shaft the speed has to be varied as you go along the shaft (this is what the Astrotrac does). So in your shoes, I'd use an Arduino, an A4988 Pololu stepper motor controller, the AccelStepper library, and one of those steppers (you could micro-step them to smooth them out, but frankly at 400 steps/rev it will not be an issue).You can also do guiding and periodic error correction with the Arduino... Are you able to tell me what rate I would need to increase the rotation speed with the Arduino if using a straight rod?