Subject:
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Re: Grade Crossing Signal Thingy...
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Newsgroups:
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lugnet.trains
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Date:
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Fri, 17 Dec 2004 21:28:37 GMT
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Viewed:
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2161 times
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In lugnet.trains, Joe Strout wrote:
> I have a couple of newbie questions about things like this.
>
> First, how do you protect the motor? In this particular design it looks like
> you could actually rotate the arm past vertical, which I guess isn't a problem
> until you hit the ground on the other side. Or, if you were to go the other
> way, you could lower the arm instead of raising it, again smashing into the
> ground. At that point, if you don't let up quick, aren't you going to strip the
> motor?
>
> This might not be a problem for AFOLs, but I'd like to have some things like
> this on a layout that would be played with by my 4-year-old, so it needs to be
> robust to abuse. Should I always go though a clutch gear? Or is there some
> other clever trick to cut the power to the motor when it goes too far?
One approach is to use a linkage mechanism in which the gate is driven by a link
that no matter how the motor rotates, never takes the gate below horizontal or
beyond directly vertical.
That of course introduces other issues, such as knowing what position you are
in, as you allude to below.
>
> A similar question applies to those nifty motorized track switches I see used at
> shows. There, even with an adult operator, it looks like it'd be easy to hold
> the button down too long and end up frying the motor. Why isn't this a problem?
Steve Ringe's mechanism uses such a link so that as you run the motor, the
switch oscillates between one position and the other.
>
> Next: when controlling a crossing like this from an RCX, is cumulated error a
> problem? I'm talking about imprecision in the position of the arm after many
> up/down cycles. I don't see a rotation sensor on this unit, so how does the RCX
> know exactly where the arm is? Or is the RCX/motor combo so precise that this
> isn't a problem?
I think this IS a problem that needs to be addressed somehow.
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Message is in Reply To:
 | | Re: Grade Crossing Signal Thingy...
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| I have a couple of newbie questions about things like this. First, how do you protect the motor? In this particular design it looks like you could actually rotate the arm past vertical, which I guess isn't a problem until you hit the ground on the (...) (20 years ago, 17-Dec-04, to lugnet.trains)
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