Old Niclk

To all the people who who have commented on this topic, especially with problems, my recent experience with a complex application may be useful. Used as directed by DCC concepts using their supplied bits and pieces they are not too bad. The following though should be noted. The instructions describe how to perform a 'reset' but do not clearly state when/if this should be done. In practice it is essential that it is the first thing you do when you have got it basically wired up and before you connect it physically to the point and adjust it. The intention may have been that the point motor was in the default position fresh out of the box - in fact this is rarely true. These small stepper motors have very little torque and can not deal with any excess friction so be careful how you set them up. Trying to push a limit switch for instance is not recommended. The adjustment for the throw although indicated as four distinct setting is actually a continuous adjustment so you can fine tune it. Be aware that the way this works is to vary a timer in the control box which determines how long the motor should operate for. There is no electronic feedback to tell the controller the motor has reached the end of its travel. If it is forced to stop moving (for any reason including friction) before the controller expects it to it will become out of adjustment and will probably not work properly again until another 'reset' is performed and you re-adjust. Also if you are driving two or more motors with one control channel then their linkages must be identical, particularly where there is any slack. Mixing point manufacturers would be very unwise. Now we come to the issue where I maintain there is a design flaw. In my conversations with DCC Concepts they have not admitted it as such but they are aware that the limitation is present and they have their own suggested work-around. The actual drive pin on the motor in which you hook the linkage wire is driven by a threaded rod and as you can see the thrust is taken off to one side rather than in-line. This means that any slight tendency for the linkage to exert pressure or a twisting moment at this point will cause the mechanism to bind and the previously mentioned low torque situation means that it will refuse to move and you are scuppered. The way they overcome this (without explaining it) is that their supplied linkage wires are thin enough and shaped so that they have some inbuilt flexibility which is intended to eliminate any such 'twisting' force. If, because of the geometry you need to fabricate your own linkage this must be replicated somehow. They use 0.3mm wire inside PTFE tubing for special longer runs of linkage and claim it works - I have yet to try it but plan to.