Subject:
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Re: Train Depot DCC Update
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Newsgroups:
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lugnet.trains
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Date:
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Mon, 15 Mar 1999 17:45:49 GMT
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Viewed:
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986 times
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Matthew Bates wrote:
> > I have a question though. Inside the LEGO motor unit is a tiny disc between
> > the one terminal of the electric motor and the metal contact stip (i.e. in
> > series). It is about 1/4" diameter and 1/32" thick, made of some black
> > substance with silvery foil on each side. What is its purpose? It doesn't
> > appear to have any resistance.
Larry Pieniazek responded:
> I am sure it has a purpose and unless you know what it is you won't know
> whether it's safe to leave out or not. Manufacturing nowadays doesn't
> typically put stuff in that's not needed, need to save those pennies.
>
> My guesses:
> capacitator (but if this is in series between the motor input and the
> contact, no way... current would not flow)
> Fusible link
OK, here's my guess. It's a polymer thermal resistive protection device.
Put it in circuit, and turn up the power...basically, no resistance.
Now, with the power up, try to stop the wheels. This would increase
the amount of current drawn by the motor, causing a heat build-up, and
potential damage to the plastic components holding the motor. This
would be a Bad Thing. So, the ploymer device, now being asked to pass
more current than it is rated for, begins to heat as well, causing the
current-passing element to become highly resistive, thus preventing the
motor from heating too much. This would cause the train motor to stop
working if it got too hot (maybe after pulling a really heavy load).
There are also thermal switches, versus this high-resistance device.
So, if LEGO uses this technology in the motors, would they also use
them in the speed controllers? This could explain some of the problems
where folks put 2-3 motors on a train, and the controller finally
quits after a while, but then resumes operation after the device has
had time to cool.
(I'm an ex-hardware-hacker, who hasn't opened his speed controller
or a LEGO motor (yet). I'm only offering one possibility. :-)
-Z- http://baylug.org/zonker
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Message has 1 Reply:
 | | Re: Train Depot DCC Update
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| Hmmm, that's a jolly fine theory, I didn't know such a material existed. Maybe I need to go back and figure out a way to incorporate the disc into the modified motor[1]. It would be kind of embarassing if my motor fell out onto the track one day (...) (25 years ago, 15-Mar-99, to lugnet.trains)
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Message is in Reply To:
| | Re: Train Depot DCC Update
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| I am sure it has a purpose and unless you know what it is you won't know whether it's safe to leave out or not. Manufacturing nowadays doesn't typically put stuff in that's not needed, need to save those pennies. My guesses: capacitator (but if this (...) (25 years ago, 15-Mar-99, to lugnet.trains)
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