Natwerk Designs

design a three way light control.?

assume a room has three doors and switch by door controls a single light in the room. let X,Y,Z denotes state of switches. assume the light is off if all switches are open. closing any switches turn the light on. closing another switch will have to turn the light off. light is on if any one switch is closed and off if two or no switches are closed. light is on if all three switches are closed.

Public Comments

1. You didn't indicate if these switches are SPST or SPDT. If the are single-pole single-throw then according to your conditions (turn any one switch on will light the lamp), all three switches must be connected to the hot wire for this to be true. If this is true then you must open the same switch to turn the light off. The other two switches will have no effect on the light. I know this is not solving your question, but the proper way to control a single light with three switches is to use two 3-way switches and one 4-way switch. I hope someone gives you a solution using 3 SPST switches. EDIT The answer I gave you yesterday is true, but perhaps you stated the question wrong. A more direct question would have been how do you control one lamp from three places. The on and off statements are of no value, if this is what you desired. As stated yesterday, the proper way to control a lamp from three different places is with two 3-way switches and one 4-way switch. Single-pole single-throw switches are the only common type of swtch which have definite 'on' and 'off' markings and positions. These switches are unmarked in regards to the on and off positions. Both positions can be either on or off, depending on the position of the other two switches. In fact, all three switches have both open and closed contacts at the same time. The second respoder included a rough 'sketch' of the use of these switches. TexMav
2. ..........2.o-------o---o------o 2 >___1_o/...........X...........\.o_1___ ..........3.o-------o---o-------o3..........I <_________________________bulb This is your circuit. 1 common, 2 n/c., 3 n/o. The center switch is a cross-over switch, with the switch in the up position phases feed from 2 to 2 and 3 to 3, in the down position phases feed 2 to 3 and 3 to 2. You need at least 3 wires, two of which will be switched phases and the third a neutral. If your light has metal it might require an earth. All power to the bulb MUST go through the switches, NOT the other way. Done that way it would leave the light socket live. Because there are two phases mark your cabling clearly identifying possible live wires for the person coming after you. Position of switches up / down is not important. Be Safe. GL>