Turntable Indexer

[AndyID]

A simple way to drive a turntable.

 

It's a very basic servo. When the motor is connected to A as shown the turntable will rotate clockwise until the A contact is no longer connected to POS or NEG. Connecting the motor to B, C or D will make the turntable rotate to park at those positions. If the turntable does happen to overshoot the motor will reverse to align the position.The indexing depends on how accurately you can make the slot between POS and NEG. It needs to be very slightly wider than the width of the wipers. Increasing the diameter of the contact segments will also improve the indexing accuracy.

 

The POS and NEG segments are fed though slip-rings.

 

A 180 degree rotation (for example from A to D) requires a brief "kick-start" to get the turntable moving, In practice that can be achieved as the selector switch contacts B or C on the way to D.

 

EDIT:

 

To keep it simple and if you don't intend to run your turntable very often, POS and NEG could be supplied from a few AA batteries.

 

 

 

 

Edited October 8, 2020 by AndyID
more info

[DCB]

I can't see how you could power this from an ordinary model railway power supply,   Surely it needs a 12v-0v-12v power unit like an old school computer PSU or batteries as per my doodle to get the 0 volt supply?   The indexing needs to be plus or minus half a millimeter for reliable running off and on the turntable.