Lever frames & Slow-mo point motors

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steve howe
Posts: 911
Joined: Sun Feb 01, 2009 10:16 pm

Lever frames & Slow-mo point motors

Postby steve howe » Wed Sep 25, 2013 8:14 am

I am thinking about using the Society lever frame for my current shunting plank since it will only require four levers for the points. In the past I have made my own slow action point motors using 6v motors with integral gearboxes that I get from a Robotics supplier. I want to put the frame onto a detached control panel so the layout can be operated from front or back.

I usually operate the motors through centre off DPDT switches on the control diagram, the 1 or 2 second pause when throwing the switch is enough for the motor to do its thing before the current cuts off when the switch is released. My problem is: how could this be related through a lever frame? I may be just missing the obvious here, but it seems that the lever operated microswitches will only ever be 'on' or 'off', can you get passing contact microswitches? or is there some cunning way of wiring the frame so that current is momentarily passed, but also reversed when the lever is returned? :?

Steve

nigelcliffe
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Joined: Mon Jul 21, 2008 8:31 am

Re: Lever frames & Slow-mo point motors

Postby nigelcliffe » Wed Sep 25, 2013 8:35 am

You need a cunning plan....

a - is it possible to put a limit switch on your motors, so that they cut-off automatically at the end of travel ? This is probably the simplest option and the reversing needs very little to sort it, just feed the circuit with AC, which is half-rectified by one of the two diodes. The switch determines which direction of diode is used:

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b - what happens if you hold the existing switch a little too long ? There will be electronics means to control the length of running time.



There are numerous solutions. My usual choice is to use Servo motors for the turnout movement, and control them with a MERG Servo4 board (or similar). The input to that board can be the microswitches on the level frame.



- Nigel
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Tim V
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Re: Lever frames & Slow-mo point motors

Postby Tim V » Wed Sep 25, 2013 4:04 pm

steve howe wrote: I usually operate the motors through centre off DPDT switches on the control diagram, the 1 or 2 second pause when throwing the switch is enough for the motor to do its thing before the current cuts off when the switch is released. My problem is: how could this be related through a lever frame? I may be just missing the obvious here, but it seems that the lever operated microswitches will only ever be 'on' or 'off', can you get passing contact microswitches? or is there some cunning way of wiring the frame so that current is momentarily passed, but also reversed when the lever is returned? :?

Steve

So how do you know in your example that the point has motored over? You don't, until the train falls off, because the route is wrong. Of course, the signal that reads through it (assuming you have interconnected/locked signals) may pull off. Have you read "design for reliability" by Stewart Hine (Feb 1976 Model Railways)? You are putting a problem into the design.

Much better to, as Nigel has suggested, have ordinary microswitches worked by the frame, with limit switches on the motors. At a glance, you will be able to look at the frame and know with certainty what the state of the route is. It is that that brings confidence into operating, without having to look at the route. And again, pulling interconnected signals off will prove the route. Signals are not an afterthought :!:
Tim V
(Not all railways in Somerset went to Dorset)

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steve howe
Posts: 911
Joined: Sun Feb 01, 2009 10:16 pm

Re: Lever frames & Slow-mo point motors

Postby steve howe » Thu Sep 26, 2013 7:28 pm

Actually Tim, my system works very well.

I just fancy a few levers to pull.


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