A new type of switch machine?

[donatode]

I have seen a variety of different methods utilized to move the points on our turnouts. Motors, rods and levers, servos etc. While surfing for some micro motors for some experimentation, i came across these little gems. They are micro stepper motors activating a linear screw. They are cheap and easily adapted mechanically to operating the turnout from below the layout. My question to our more electronically knowledgeable brothers, how hard would it be to wire these little puppies to do the job without going into too much elaborate use of micro controllers....just a plain dpdt switch...!!

http://www.ebay.com/itm/DC5V-2-Phase-4-Wire-Miniature-8mm-Stepper-Motor-Mini-Stepping-Motor-Linear-Screw-/263016192408

[jbvb]

The reason they're called 'stepper motors' is because they move in increments.  Typically, there are multiple coils.  You hold it in place by putting voltage on one coil.  You move it one step by putting the voltage on two or three more coils, in sequence, then switching it back to the first.  You could run one of those by twiddling a rotary switch, but your wrist would get tired long before you got the points from one locked position to the other: most steppers only turn a few degrees per cycle.

[donatode]

Thanks James, didn't realize that.

[Jim Donovan]

I just found this thread and the motors look very interesting. So what would thy be good at?

[friscomike]

Perhaps animation, e.g., water tank spouts, signals, people moving... ~mike c

[jbvb]

Jim, stepping motors are designed for precise positioning, at the cost of slow (with lots of tiny steps) or jerky (fewer, larger steps) motion getting to the position.  They first appeared on the modeling scene as salvage from dead dot-matrix printers.  Once you've got the control electronics set up correctly, if it takes exactly 29 steps to move a turntable or crane from one position to the next, that's what the stepper delivers.  Many of the common stepper drivers can reverse too, and change the interval between steps for variable speed.  Running a stepper slower with direct drive usually gives much better precision than a gear train with fast steps.

[Blazeman]

So would one use the shortest unit (19MM) for moving switch points?  How much time is estimated to complete the moving?

[bparrish]

This is an interesting conversation that keeps coming around.

These are not new.   I played "pass the box" with a modeler friend for nearly twenty years with a bunch of these.  They were a bit different and actually designed to be under the bench mounted....  But they have their draw backs.

I followed the link shown in the opening thread and looked at they photos.  These are not steppers.  They might be capable of it but not as shown.  There are four contacts shown but only two have wires to them.  That would be the motor drives.

The only way to run these safely is to have a center off position toggle switch and a double throw that the operator would hold and watch the switch points move and then let off the switch.  A spring wire could be used so as to not over load the turnout. 

Elaborate contacts could be used as location sensors but for the price and availability of tortoise machines... why stray very far from them.

It is an interesting conversation.

thanx
Bob