Hi Chris,
Quote:
Originally Posted by chrisp9au
I envisage a handset with momentary switches for forward and reverse slewing, and a speed adjustment potentiometer(?) to reduce speed when at the eyepiece.
I think I could manage that, momentary switches that reverse the wiring for change of direction, plus the potentiometer.
Is it that simple?  |
Yes, but.. there will be power dissipation issue if you use those motors (any resistor in series with motor may get quite hot, depends on current/voltage... so you may end up with a need to introduce relays and to cool potentiometeres ( or to use wire-wound variety, not easy to find these days).
Astro-nutt's advice may be better - use a small motor with gearbox, just for adjustment/correction of position while you are observing. The coupling with your dob shafts may be frictional (with rubber wheels, for example).
However, very soon you will want more so I think you should go straight with stepper motors - later it will be much easier to upgrade to GoTo system (actually you are almost already there with steppers).
Recently I did some evaluation work on stepper driver chips, those Pololu drivers (or their clone, StepStick) are cheap, and work really well (threads are in this section,
http://www.iceinspace.com.au/forum/s...ad.php?t=90164,
http://www.iceinspace.com.au/forum/s...ad.php?t=91039).
The cost is ~$15 for driver module (Pololu or Stepstick), ~$10 for stepper motor, and couple of bucks for other stuff (inverter gates, connectors, wires, protoboard..). Multiply this by 2x for two axis control.
And what's more, they are compatible with both bartels scope.exe and Maciel's SoundStepper sofware (for this you have to invest ~$10-more for sound modules, some more connectors, switches, box...) and voila, you have full blown GoTo system if you add Cartes du Ciel or Stellarium to that mix.
The only (small) drawback is, you have to carry your laptop with your dob. But when you consider all the capabilities you are getting...