Thursday, 8 February 2018

switches - Can this double-pole double-throw switch be simplified for controlling a motor (skylight)


I'm considering retrofitting skylight motors but would like to know if I can use standard home switches to control it. I have not found examples of up, down and open switches (is this 3 pole, normally open?). I imagine this should be similar for blinds or any motor that steps in two directions (but not just fully open or fully closed like a garage door).


The skylight manual contains this diagram, first below.



The second I simplified because I don't understand the need for a double-pole, double throw where the Neutral disconnects when untouched. Any ideas why they would want that?


Finally the third diagram shows my idea to use two momentary switches which I believe should work. However would anyone be able to speculate if the motor is likely to have protection against both open and closed being pressed simultaneously? Am I overlooking anything else?


wiring diagram


Update The winning solution is: https://electronics.stackexchange.com/a/340685/169328


The local supplier of one brand, Topp, that operates at mains voltage supplied the following diagram with matches second circuit diagram 2(b).


Switch Wiring Diagram for Topp C20 actuator


This uses two common momentary switches. Note how 2 feeds into C of the second switch.



Answer



schematic


simulate this circuit – Schematic created using CircuitLab



Figure 1. (a) Probable wiring scheme. (b) Typical limit-switch wiring.


You are probably correct in thinking that the neutral need not be switched. The manufacturer may have had some reason to prefer that the motor is fully isolated though so you should check the motor units to see.


schematic


simulate this circuit


Figure 2. Possible solutions using standard domestic single-pole, 2-way switches. Both circuits prevent attempting to run both motor coils simultaneously.


You should have no difficulty in obtaining a changeover switches and wiring them as shown in Figure 2.


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