Subject:
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Re: Some help or advice requested
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Newsgroups:
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lugnet.technic
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Date:
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Fri, 22 Jan 2010 20:42:24 GMT
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Viewed:
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19957 times
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In lugnet.technic, Owen Dive wrote:
> Hi all.
>
> I am currently working on a project (to be revealed in due course!) and I've
> come across something of a stumbling block. I have a tray that is constrained to
> move in one dimension, and a series of short liftarms under the tray, all
> rotating in phase with each other, and placed such that once per rotation, they
> connect with the tray (ok, so the tray can move vertically as well, but only a
> little bit!) and move it along a specified distance. So far so good. What I need
> is for the motor to change direction when the tray has reached the limit of its
> travel, and to have such a mechanism at each end of the track, so the tray moves
> back and forth for as long as power is supplied. Make sense?
<snip>
Hi Owen,
As you say, you want a mechanism where the switch wants to be either on or
off, but not in the middle. Had you thought about adding a pivot point at the
top of the switch handle, with an axle going up and a weight at the top.
Imagine the right hand switch, switched to the left, and the pivot having the
weight directly above the pivot. The tray slides right, hits the axle, tipping
the weight to the right. There is a limit on the pivot, so the weight's
momentum then forces the switch to flip. Presuming you can do that, then all
you have to do is somehow get the weight back to the starting position.
This solution may not work, but it is worth a try. The word hysteresis comes
to mind, but I'm not sure that is really the case here. I know the problem well
though... Imagine a pneumatic piston flipping a pneumatic switch, but the
switch's outputs control the piston. Once you hit the off position everything
stops. Like you, I worked out a rubber band based mechanism where the switch
hated to be off:
http://www.kclague.net/oscillator/index.htm
But given you already found one of my other "no off" solutions, you probably
found this one as well.
Kevin
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Message has 1 Reply:
 | | Re: Some help or advice requested
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| (...) Hmm, an interesting solution. (...) But there's the rub! I'm afraid I can't see an obvious way to do that, given that the weight will need to be positioned quite precisely. I will play around with it, though, and see what I can come up with. (...) (14 years ago, 22-Jan-10, to lugnet.technic)
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Message is in Reply To:
| | Some help or advice requested
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| Hi all. I am currently working on a project (to be revealed in due course!) and I've come across something of a stumbling block. I have a tray that is constrained to move in one dimension, and a series of short liftarms under the tray, all rotating (...) (14 years ago, 19-Jan-10, to lugnet.technic)
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