TWO GROUPS OF LAMPS CONTROLLED FROM THE SAME LOCATION (THEORY)

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A typical need for an electrical system, concerns the control of two (or more) groups of lamps from the same location. The common case is a chandelier with three light bulbs

for which we want to be able to turn on only one light bulb

or two light bulbs

or finally all three light bulbs.

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A possible solution to the problem is to use two single-pole single-throw switches, where one switch is connected to a single light bulb (which in general could represent a first group of lamps) while the other switch is connected to the remaining two light bulbs (which therefore represent the second group of lamps).

The circuit diagram is illustrated in the following figure.

We can see that when both switches are open all light bulbs are off.

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When the switch placed at the top of the diagram is closed, only one light bulb turns on, as desired.

When we close the switch at the bottom of the diagram and at the same time we open the switch at the top of the diagram, two light bulbs will turn on, as desired.

Finally, when both switches are closed, all three bulbs will turn on.

We can therefore conclude that we are able to obtain the required functionality. In particular, with the diagram just illustrated, we can control the number of light bulbs to be turned on from the same position in the room.

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