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Re: [TowerTalk] Connecting limit switches on a tower winch

To: Dan <>,
Subject: Re: [TowerTalk] Connecting limit switches on a tower winch
From: Jim Lux <>
Reply-to: Jim Lux <>
Date: Tue, 27 May 2008 17:50:53 -0700 (GMT-07:00)
List-post: <">>
It's pretty easy, but tricky to explain in words.

I'll explain for a DC motor first..

THe switches are mounted and connected so they are normally closed, and when 
you hit the limit, they OPEN, interrupting current flow.

Say that positive goes UP and negative goes DOWN.  You put the limit switches 
in with a diode across it. the switch at the TOP (limiting UP travel) has the 
diode across it so that when the voltage applied to the motor is negative, the 
diode carries the current. Even if the switch is open, the motor can still move 
The DOWN limit switch is wired with the diode the other way.

You can also wire the limit switches in parallel with the diode in series.  The 
diode that is forward biased when going up is in series with the UP limit, and 
the one that is forward biased when going down is in series with the DOWN limit.

For reversible AC motors, it depends on how you're doing the reversing and what 
kind of motor it is. Typically, it requires a DPDT reversing switch (instead of 
the usual SPDT) and hooking the limit switch in series when going the 
appropriate direction.

-----Original Message-----
>From: Dan <>
>Sent: May 27, 2008 5:05 PM
>Subject: [TowerTalk] Connecting limit switches on a tower winch
>I came across this reflector after doing a search on tower winches.
>I mounted a Dayton AC winch with forward reverse to my Hy Gain HG55SS Crank
>up tower. It works like a charm, but I want to mount two limit switches on
>I have two Allen Bradley 802T switches, the same used on some commercial
>Since I cannot afford a $2000 solution from the commercial tower companies,
>I hope someone on this reflector has done what I want to do, or can provide
>me with a wiring diagram on how to go about this.
>Any help would be greatly appreciated.

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