stepping motors and watthers turntable

The All Electronics stepper motors are just fine. You might want to try #SMT-46 as it gives you 0.9 degrees/step. Hope you realize you don't just hook these up to voltage and away you go. You need a stepper motor controller!

That looks like a really nice stepper, must bookmark it. Also, further to Jon's comment about needing a controller, you will need a Bipolar controller for that stepper motor. (stepper motors come in unipolar and bipolar) Try:

for a good review/tutorial on the subject.

David

J> The All Electronics stepper motors are just fine. You might want to try

The trick is to have automatic shutoffs for the DC motor so that it stops at approximately the same point each time. Then you can do fine positioning with pushbuttons if so desired. The usage of photodiodes and so forth under each track can also automate that process to an accuracy that is good enough to keep locos from bouncing as they cross the divide. It is just a matter of minor design and building the electronics to do these things

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works every time it is tried!

Even a .9 Deg stepper motor will be too jerky as is for a turntable. You will need to gear or belt it down to get good movement. I have been experimenting with a micro stepper driver is 3977 from Allegro. But even with 8 steps per whole step you have don't want to spend much time at the slow speeds as the jerkyness is still apparent.

Best Regards,

Ken Harstine

[This followup was posted to rec.models.railroad and a c> I have, afer much travail, assembled and installed the walthers ho

I'm trying to find a tight gear set so I can do somewhere between

5 and 20 to 1 reduction. I figure I can use a 1.8 degree stepper at 20 to one and have the jerkiness minimized. According to the "Tutorial" that David indirectly pointed to,

"

" you can sacrifice torque for smoothness?

Paul

Yes, and while 0.9 degrees per step is better than average for stepper motors, it's still FAR too coarse an increment to align a turntable with adjoining tracks. So, some gearing will be needed, probably something like 10:1 reduction. That will give, approximately, a 0.1 degree resolution ... probably about minimal for acceptable alignment. More reduction would be better. The longer the turntable, the greater the precision in alignment needed.

Dan Mitchell ==========

J>

Ken you have got to get your controller ready for market!!!!!

I gave up on trying to do it myself and bought a PTC model II unit. Expensive but really good. They use geared stepper motors.

First site is the current owner of the product and second site still has data on it.

Worm gear sets from the gear makers like Boston Gear and so forth aren't that expensive and provide a fairly tight gearing for a turntable. In addition, you always want to set a forward direction and a reverse direction for the table and when doing a reverse motion of the table, overshoot the position and go back in the forward direction to get the right position. Make the reverse overshoot adjustable in the software of the controller and you will be able to have to hardly move the table to get the right position when going in the forward direction.

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works every time it is tried!

Thanks for the heads up on suppliers

I'll try to remember that, thanks again.

Paul

This question comes from someone who is electronically challenged: What is a stepper motor and how does it help the turntable operation?