Subject:
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Re: Reed Switches was Re: Has Babylon Fallen?
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Newsgroups:
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lugnet.trains
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Date:
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Mon, 27 Nov 2006 19:43:02 GMT
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Viewed:
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5056 times
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In lugnet.trains, Lawrence Livesey wrote:
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In lugnet.trains, Chris Phillips wrote:
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In lugnet.trains, Elroy Davis wrote:
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In lugnet.trains, Christopher Masi wrote:
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You know, it was always fun talking with you at the events, but I have
got to admit, I really miss those crossing gates that you have. Those
things are AWESOME.
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Oh yeah! I remember seeing those at a show before I joined NELUG. I went
out that day and bought some reed switches. The next day I spent a few
hours burning my fingers and melting the things together. I never did get
them to work properly.
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The reed switch
sensors are a bit tricky. There’s not much room to work with, so you’ve
gotta use pretty small switches.
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Miniatronics makes nice
reed switches that seems to work well.
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Good link!
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And they are very easy to break, basically
being tiny glass tubes. (About half of my sensors no longer work.)
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Yes, you have to grab the lead in wire up close to the glass envelope with a
pair of needle nose pliers, and, while holding the pliers you bend the wire.
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I don’t bend the leads on the reed switches at all. I use very small reeds,
maybe 1 cm in length, solder directly to the straight leads, and then carefully
trim them shorter. (Trimming is optional.) The switch is then sandwiched
between a 2x2 plate and a 2x4 plate that have been modified with a dremel tool.
The result is a very flat sensor that will not interfere with the underside of a
passing train. In fact, there is usually enough clearance to “dress up” the top
of the sensor with a pair of 2x2 or 1x4 tiles, if desired. Even though this
operation is Evil on many levels, the end result looks like a pure-LEGO solution
to the untrained eye.
The way I’ve broken switches is by applying too much pressure to the sensor
housing when placing them on the track. A small amount of flex will break the
glass. Sometimes a cracked or broken reed will work intermittently, so it can
be frustrating to diagnose.
I know that some of the custom MindStorms sensor guys are keen on using
hall-effect devices as train sensors, but these are active electronics
(basically a magnetically-sensitive transistor) so you need to add the six-diode
rectifier circuit, etc. This would probably be more durable, but makes for a
much more complex project.
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Message is in Reply To:
 | | Reed Switches was Re: Has Babylon Fallen?
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| (...) Miniatronics makes nice (URL) switches> that seems to work well. (...) Yes, you have to grab the lead in wire up close to the glass envelope with a pair of needle nose pliers, and, while holding the pliers you bend the wire. (...) Those are (...) (18 years ago, 27-Nov-06, to lugnet.trains, FTX)
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