Planetarium Star Projectors

[m2b]

Ah, great!
5.4 in lb is 0.61N accordning to http://www.boltscience.com/pages/convert.htm and my motors have a 2N rating.
I have drivers with both 1000 and 10.000 microsteps and even one with "analog mode" that are used for star tracking telescopes, will try and see if that will be necessary.
1725 rpm / 18 is 95 rpm, I dont know what torque the motors have left at that RPM, they are speced at 1000 rpm I think but I guess I'll have to try!

I was thinking of putting the motors up on the worm drive with a belt drive instead of the shafts, do you see a problem with that? I read something about the motors obstructing the starfield in the thread, but is that only regarding projectors with dual starballs?
I could use a 1:2 or 1:4 pulley ratio to gain more torque if needed.

I believe the torque rating is at the output shaft after the gear box so it is 5.4 inch/lbs at the 95rpm output. Also remember that you would seldom run the motor at full speed as a day would zoom by in a minute or so. More often during a demonstration you would want a day to run by in 5 to 20 minutes depending on the lecture. You would probably only use the fast speed to reset the projector between shows, unless of course you just wanted an eye candy demo to go with a laser show.

The motors were indeed placed below the base plate so they would not block the various projectors. When showing a northern sky, the star ball is above the horizon axis so no problem, but there are many times when one of the planet projectors would be blocked. If you take the machine to a southern latitude then the star globe would be below the axis and anything mounted to that axis would block star projection. A projector with dual starballs has less of a problem as each hemispheres stars are projected away from the central core.

[dar303]

Thanks for clarifying all this for me! There are a lot of new concepts to take in for a beginner in the planetarium biz!

I am trying to locate the original motors and transmission but they may have re-used it for something else at the museum.

I read a lot over at OC in the thread "Ron's A3P" and that gave me a bit clearer picture of how the machine works. I'm not going to attempt that fantastic modification that made all the planetary movements work with only one motor, that would take me a lifetime! I think i'll try a shot at building new electronics for the motors, I understand that you vary the frequency to control the motors from about 60hz and down and that they are all driven in parallell by a squarewave signal right?
But what voltage and current does the motors require?

I'm starting out slowly by restoring the orrery, it had a broken lamp socket, a loose lens holder and some glass shards between lenses in the Venus-projector, very interesting and well built machine!
I'm adding a 5V switching PSU and a little control panel for stand alone operation, my oldest son (6) wanted me to show it at his school the day after tomorrow so I better get it going!

[m2b]

The standard motors in the USA are 120vac and pull 5 watts each. The original electronics generated the 60Hz and down. Basically full speed (a year in about a minute) could be run directly off of the ac line. I'm not sure what your standard voltage and frequency are over there and I'm not at all sure if Spitz used different motors dependent on what the line was in different countries. If your mains are 240v my guess is that Spitz would have just included a large step down transformer.

One of the interesting things that Spitz did do with original electronics is add a 24vdc electronic brake to the system. The motors would all turn in sync as long as power was supplied but when turned off they would coast to a stop. Do to the mechanical load on each different planet drive, the motors would tend to "coast" to a stop at different rates and thus throw off the proper positions of the various projections. The reason I went for the complete mechanical drive rather then keeping the separate motors is that the relationship between the Earth and the Sun should remain identical on all of the drives. Once set, there is no variation between the various projectors and no slippage at all. Besides, it was fun to see if it could be done.

As I'm sure you know the orrery will need to move from where is is in the picture.

It is interesting how these strange mechanical devices bring out the "kid" in all of us. To see the eyes of a child light up even before the projector projects does ones heart good.

But, the day after tomorrow...???...???

[SpitzSTP]

Work continues down in mission control, hours (no, days) consumed in rather mundane prepatory tasks, but progress nonetheless on the full-dome projection system. Two PC's networked to the HD24 through a baseline switch. The newly-built PC now stable, this was far easier said than done

[m2b]

Work continues down in mission control, hours (no, days) consumed in rather mundane prepatory tasks, but progress nonetheless on the full-dome projection system. Two PC's networked to the HD24 through a baseline switch. The newly-built PC now stable, this was far easier said than done

Good to see work continue.

I still want to work on that other piece of equipment. I thought you were coming up.

[SpitzSTP]

Good to see work continue.

I still want to work on that other piece of equipment. I thought you were coming up.

Sorry for the delay. I hope to bring it to you soon (Conic Orrery, to be restored).
With about 100 hours of work, the new Omniscan PC is further along. The challenge now is to resolve an address conflict between the QM32 board and the SMPTE/MIDI board. But, it's getting there. I will be researching PL to see if there are any tips out here for resolving QM32 / ISA address / IRQ conflicts as this seems to be the case now. Update: thanks to the tips on PL, I resolved the IRQ conflict through BIOS adjustment and disabling pnp -- and it ALL works.

[SpitzSTP]

I put the switch in the back with a label for all the IP addresses. I had a hard time figuring out how to setup the network until someone turned me on to Wireshark. Ready to cable it all up and see what happens. Last time Karl and Swami were over we used an ALC60X, next time we'll use the HGM8.

[m2b]

There is something about computers that tend to drive me up a wall. I think as I grow older, I can't logically think things through anymore. Give me a switch any day and not software.

[SpitzSTP]

There is something about computers that tend to drive me up a wall. I think as I grow older, I can't logically think things through anymore. Give me a switch any day and not software.

Then this thing will be right up your alley. I cannot find the cables that connected it to the PSU, unless they are in the boxes from Gillette. May have to make them. It also has ten years of dust on it, just the way you like it, barn fresh.

[m2b]

Then this thing will be right up your alley. I cannot find the cables that connected it to the PSU, unless they are in the boxes from Gillette. May have to make them. It also has ten years of dust on it, just the way you like it, barn fresh.

Love it, love it, love it!