Limit switches and reversed polarity

Thread Starter


Joined Aug 16, 2019
Hello i wanted if someone can help me with a circuit but in a way i can understand because i am dont know much.
I want to attach 2 external limit switches in a linear actuator and i want with a third limit switch (like a trigger) to operate the system as follows:

I want when i press the 3rd limit switch the actuator to start expanding and when it reaches the first limit switch to stop. When i let go the 3rd limit switch i want the actuator to go back all alone and when it reaches the 2nd limit switch to stop permanently unless i press the 3rd limit switch again and the system starts again .

If you didn't understand i want to press a limit switch and the actuator starts going forward and when it reaches the front limit switch to stop and remain stoped. But if i let go the limit switch i want the actuator going back (retracts) and when it reaches the back limit switch to stop again and restart this motion only if i press again the limit switch working as trigger

So i want to use limit switches because they are small and i think i ll probably need a relay that i can put it in an other spot


Joined Feb 25, 2011
How about drawing us a diagram of the sort of mechanics your after,
and a state diagram of the three switches and the expected action


Joined Mar 14, 2008
Will this do what you want?
It uses two relays besides the three limit switches.
Note that you may need to add 4 suppression diodes to protect the relay contacts from the actuator motor inductive spikes.

The limit switches are shown for the retracted state.

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Joined Aug 1, 2013
If switch 3 is DPDT, then you don't need a relay. This schematic is from another thread. Instead of reed switches, use the NC (normally-closed) contacts on your limit switches.

If switch 3 must be a SPST or SPDT limit switch, use it to control a DPDT relay in the place of SW1 (switch 3 in your description).

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