There are several ways to mechanize limit switches, including:
Mechanical arrangements such as micro switches with a lever or similar
that is pushed to change state on contacts either open to closed or
closed to open depending on the particular design.
Reed switches and magnets or Hall effect devices and magnets.
Optical, typically an LED and a photoreceptor not unlike the safety
mechanism that controls a garage door. Your kid or dog breaks the beam
and the door stops and maybe reverses. Same idea for tower sections
moving with respect to one another. Components are readily available at
OVERHEAD DOOR or probably the big box store but I don't know this latter
for a fact. A DIY project, not a super simple kit.
Some limit controls are current sensing. When the mechanical limit is
reached the current drawn by the motor spikes to a value above the
normal operating current which is sensed by the controller which kills
the power to the motor.
There may be other mechanisms in use (maybe some humorous Rube Goldberg
ones) but I am not familiar with any others in use if there are any.
There was a fellow with an experimental controller that had a follow up
pot like a rotor. You dial in a height and the tower motor ran the
tower to that height. I think his system had micro switches with levers
as fail safe limit switches for just in case.
73,
Patrick NJ5G
On 5/14/2014 4:16 PM, Steve Baughn wrote:
I was fortunate enough to just acquire one of these towers. It was taken
apart-cabling,nuts,bolts, motor etc. and the previous owner decided to moved
rather than put it back together. Is anyone on TT familiar with this tower or
perhaps have a manual that I could get a copy of? I want to make sure I get all
the cabling and parts back where they belong. I have a call in to U.S. Tower
but have not heard back from them. I saw that this tower did not have limit
switches with it unless you purchased the remote control. Has anyone fabricated
their own remote switch w/limits that they could share the diagram on? I am not
familiar with how the limits mount on the tower or where. Many thanks!
73,
Steve Baughn, WD8NPL
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