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Lead screw limiters for motor - RF Cafe Forums
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| troy
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Post subject: Lead screw limiters for motor
Posted: Mon Feb 25, 2008 4:57 pm
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Joined: Mon Feb 25, 2008
4:53 pm
Posts: 10 |
Hey guys I'm using a car window motor to
drive a lead screw with the standard automotive
12V system. Is there a simple way to put something
inline so when the leadscrew reaches the end of
the travel and hits a stop, it stops the current
to the motor. the stock unit must have something
built in but I need different limits. Im trying
to avoid mechanical limit switches. Troy
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nubbage |
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Post subject:
Posted: Tue Feb 26, 2008 5:19 am
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Joined: Fri Feb 17, 2006
12:07 pm
Posts: 304
Location: London UK
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Hi Troy
If you are against mechanical limit
switches because of dust, then you might consider
a ceramic magnet on the traverse driven by the lead
screw , which operates a reed relay at the limiting
points.
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troy |
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Post subject:
Posted: Tue Feb 26, 2008 11:27 pm
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Joined: Mon Feb 25, 2008
4:53 pm
Posts: 10 |
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Thanks Mr. Nubbage
I am using this to open
and close a vent in a shop so you're right that
I am worried about dust and other crap in the air
(including bugs). I need to open the unit and see
where the existing limit switches connect into the
circuit. So do you have a manufacturer to suggest
for your kind of limit switch, or should I just
do an Internet search for something? I'm guessing
the current level that the switch needs to carry
is pretty low so just about anything will work?
Thanks.
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nubbage |
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Post subject:
Posted: Wed Feb 27, 2008 7:44 am
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Joined: Fri Feb 17, 2006
12:07 pm
Posts: 304
Location: London UK
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Hi Troy
The beauty of the approach is that the
components are readily available and very tolerant
of environment.
Just google for "ceramic magnets"
and "reed relays", and that should throw up a number
of local sources in your area. When you have a handfull
(and they are inexpensive) just fiddle around with
different arrangements on a test fixture until you
get reliable switching every time.
Reed relay
contact ratings go up to several amps, and the sensing
distance for the ceramic magnet is several millimetres,
so tolerances are relaxed whilst still ensuring
reliable operation. Ceramic magnets, as you might
guess, are high-energy types and can operate up
to quite high ambient temperatures without demagnetizing.
Give us some feedback how the project is going
later.
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Posted 11/12/2012
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