Anyone tried using a stepper motor? I put together a circuit that will half-step a 1.8 deg./step motor. This circuit allows adjustable speed at 400 steps per 360 deg. but still in operation it vibrates as it rotates. I haven’t yet placed a turntable(N scale) on it so I don’t know if it would be OK. I like the idea of precise track alignment a stepper would allow.
I tried a few different stepper motors but they were too jerky for my taste. I ended up using a Walthers motor kit. Still a bit jurky in spots but the problem is the turntable being made of plastic and not metal ( I have a HO scale Heljan T.T.).
A geared motor that operates with variable voltage works best.
However, New York Railway Supply ( http://www.nyrs.com ) uses a stepper motor for their indexing system. So give it a try since you went through all the trouble making a curcuit for it. Just don’t hack up the turntable in case you have to go back to the drawing board.
Good Luck!
G.
Two things, you need to increase the rotational inertia ot the system, and if desired, add some damping to the system.
Adding brass beams, and hidden weights will increase the rotational inertia.
A couple of heavy wieghts, one each end of the TT mounted in latex rubber work fairly well as dampers and increasing the rotational inertia. The wieghts should be as close to identical as possible, and mounted to maintain the balance of the turn table.
Use as small a stepper motor as you can get away with - to reduce the forces and vibrations that it puts into the system. Also try some waveform shapping, closer to sinusoidal rather than square.
Do NOT use a flexible coupling between the motor and the TT. Make it as rigid as possible.
FYI; I am design engineer and work on control systems - this sort of thing is what I do for a living.
Thanks gsetter, I’ll go and look at that site.
And thanks to you mfmisso, weights and a change of wave-form could help, possibly with a rising wave and not the square. It will take some major changes to my circuit for I am using a 1-of-10 output chip to get my 8-step pulses. My circuits are made on a Radio Shack breadboard so I can try new things fairly easy.